src/Doc/System/Server.thy
author wenzelm
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     1 (*:maxLineLen=78:*)
     2 
     3 theory Server
     4 imports Base
     5 begin
     6 
     7 chapter \<open>The Isabelle server\<close>
     8 
     9 text \<open>
    10   An Isabelle session requires at least two processes, which are both rather
    11   heavy: Isabelle/Scala for the system infrastructure and Isabelle/ML for the
    12   logic session (e.g.\ HOL). In principle, these processes can be invoked
    13   directly on the command-line, e.g.\ via @{tool java}, @{tool scala}, @{tool
    14   process}, @{tool console}, but this approach is inadequate for reactive
    15   applications that require quick responses from the prover.
    16 
    17   In contrast, the Isabelle server exposes Isabelle/Scala as a
    18   ``terminate-stay-resident'' application that manages multiple logic
    19   \<^emph>\<open>sessions\<close> and concurrent tasks to use \<^emph>\<open>theories\<close>. This provides an
    20   analogous to @{ML Thy_Info.use_theories} in Isabelle/ML, but with full
    21   concurrency and Isabelle/PIDE markup.
    22 
    23   The client/server arrangement via TCP sockets also opens possibilities for
    24   remote Isabelle services that are accessed by local applications, e.g.\ via
    25   an SSH tunnel.
    26 \<close>
    27 
    28 
    29 section \<open>Command-line tools\<close>
    30 
    31 subsection \<open>Server \label{sec:tool-server}\<close>
    32 
    33 text \<open>
    34   The @{tool_def server} tool manages resident server processes:
    35   @{verbatim [display]
    36 \<open>Usage: isabelle server [OPTIONS]
    37 
    38   Options are:
    39     -L FILE      logging on FILE
    40     -c           console interaction with specified server
    41     -l           list servers (alternative operation)
    42     -n NAME      explicit server name (default: isabelle)
    43     -p PORT      explicit server port
    44     -s           assume existing server, no implicit startup
    45     -x           exit specified server (alternative operation)
    46 
    47   Manage resident Isabelle servers.\<close>}
    48 
    49   The main operation of \<^verbatim>\<open>isabelle server\<close> is to ensure that a named server is
    50   running, either by finding an already running process (according to the
    51   central database file @{path "$ISABELLE_HOME_USER/servers.db"}) or by
    52   becoming itself a new server that accepts connections on a particular TCP
    53   socket. The server name and its address are printed as initial output line.
    54   If another server instance is already running, the current
    55   \<^verbatim>\<open>isabelle server\<close> process will terminate; otherwise, it keeps running as a
    56   new server process until an explicit \<^verbatim>\<open>shutdown\<close> command is received.
    57   Further details of the server socket protocol are explained in
    58   \secref{sec:server-protocol}.
    59 
    60   Other server management operations are invoked via options \<^verbatim>\<open>-l\<close> and \<^verbatim>\<open>-x\<close>
    61   (see below).
    62 
    63   \<^medskip>
    64   Option \<^verbatim>\<open>-n\<close> specifies an alternative server name: at most one process for
    65   each name may run, but each server instance supports multiple connections
    66   and logic sessions.
    67 
    68   \<^medskip>
    69   Option \<^verbatim>\<open>-p\<close> specifies an explicit TCP port for the server socket (which is
    70   always on \<^verbatim>\<open>localhost\<close>): the default is to let the operating system assign a
    71   free port number.
    72 
    73   \<^medskip>
    74   Option \<^verbatim>\<open>-s\<close> strictly assumes that the specified server process is already
    75   running, skipping the optional server startup phase.
    76 
    77   \<^medskip>
    78   Option \<^verbatim>\<open>-c\<close> connects the console in/out channels after the initial check
    79   for a suitable server process. Also note that the @{tool client} tool
    80   (\secref{sec:tool-client}) provides a command-line editor to interact with
    81   the server.
    82 
    83   \<^medskip>
    84   Option \<^verbatim>\<open>-L\<close> specifies a log file for exceptional output of internal server
    85   and session operations.
    86 
    87   \<^medskip>
    88   Operation \<^verbatim>\<open>-l\<close> lists all active server processes with their connection
    89   details.
    90 
    91   \<^medskip>
    92   Operation \<^verbatim>\<open>-x\<close> exits the specified server process by sending it a
    93   \<^verbatim>\<open>shutdown\<close> command.
    94 \<close>
    95 
    96 
    97 subsection \<open>Client \label{sec:tool-client}\<close>
    98 
    99 text \<open>
   100   The @{tool_def client} tool provides console interaction for Isabelle
   101   servers:
   102   @{verbatim [display]
   103 \<open>Usage: isabelle client [OPTIONS]
   104 
   105   Options are:
   106     -n NAME      explicit server name
   107     -p PORT      explicit server port
   108 
   109   Console interaction for Isabelle server (with line-editor).\<close>}
   110 
   111   This is a wrapper to \<^verbatim>\<open>isabelle server -s -c\<close> for interactive
   112   experimentation, which uses @{setting ISABELLE_LINE_EDITOR} if available.
   113   The server name is sufficient for identification, as the client can
   114   determine the connection details from the local database of active servers.
   115 
   116   \<^medskip>
   117   Option \<^verbatim>\<open>-n\<close> specifies an explicit server name as in @{tool server}.
   118 
   119   \<^medskip>
   120   Option \<^verbatim>\<open>-p\<close> specifies an explicit server port as in @{tool server}.
   121 \<close>
   122 
   123 
   124 subsection \<open>Examples\<close>
   125 
   126 text \<open>
   127   Ensure that a particular server instance is running in the background:
   128   @{verbatim [display] \<open>isabelle server -n test &\<close>}
   129 
   130   The first line of output presents the connection details:\<^footnote>\<open>This information
   131   may be used in other TCP clients, without access to Isabelle/Scala and the
   132   underlying database of running servers.\<close>
   133   @{verbatim [display] \<open>server "test" = 127.0.0.1:4711 (password "XYZ")\<close>}
   134 
   135   \<^medskip>
   136   List available server processes:
   137   @{verbatim [display] \<open>isabelle server -l\<close>}
   138 
   139   \<^medskip>
   140   Connect the command-line client to the above test server:
   141   @{verbatim [display] \<open>isabelle client -n test\<close>}
   142 
   143   Interaction now works on a line-by-line basis, with commands like \<^verbatim>\<open>help\<close> or
   144   \<^verbatim>\<open>echo\<close>. For example, some JSON values may be echoed like this:
   145 
   146   @{verbatim [display]
   147 \<open>echo 42
   148 echo [1, 2, 3]
   149 echo {"a": "text", "b": true, "c": 42}\<close>}
   150 
   151   Closing the connection (via CTRL-D) leaves the server running: it is
   152   possible to reconnect again, and have multiple connections at the same time.
   153 
   154   \<^medskip>
   155   Exit the named server on the command-line:
   156   @{verbatim [display] \<open>isabelle server -n test -x\<close>}
   157 \<close>
   158 
   159 
   160 section \<open>Protocol messages \label{sec:server-protocol}\<close>
   161 
   162 text \<open>
   163   The Isabelle server listens on a regular TCP socket, using a line-oriented
   164   protocol of structured messages. Input \<^emph>\<open>commands\<close> and output \<^emph>\<open>results\<close>
   165   (via \<^verbatim>\<open>OK\<close> or \<^verbatim>\<open>ERROR\<close>) are strictly alternating on the toplevel, but
   166   commands may also return a \<^emph>\<open>task\<close> identifier to indicate an ongoing
   167   asynchronous process that is joined later (via \<^verbatim>\<open>FINISHED\<close> or \<^verbatim>\<open>FAILED\<close>).
   168   Asynchronous \<^verbatim>\<open>NOTE\<close> messages may occur at any time: they are independent of
   169   the main command-result protocol.
   170 
   171   For example, the synchronous \<^verbatim>\<open>echo\<close> command immediately returns its
   172   argument as \<^verbatim>\<open>OK\<close> result. In contrast, the asynchronous \<^verbatim>\<open>session_build\<close>
   173   command returns \<^verbatim>\<open>OK {"task":\<close>\<open>id\<close>\<^verbatim>\<open>}\<close> and continues in the background. It
   174   will eventually produce \<^verbatim>\<open>FINISHED {"task":\<close>\<open>id\<close>\<^verbatim>\<open>,\<close>\<open>\<dots>\<close>\<^verbatim>\<open>}\<close> or
   175   \<^verbatim>\<open>FAILED {"task":\<close>\<open>id\<close>\<^verbatim>\<open>,\<close>\<open>\<dots>\<close>\<^verbatim>\<open>}\<close> with the final result. Intermediately, it
   176   may emit asynchronous messages of the form \<^verbatim>\<open>NOTE {"task":\<close>\<open>id\<close>\<^verbatim>\<open>,\<close>\<open>\<dots>\<close>\<^verbatim>\<open>}\<close>
   177   to inform about its progress. Due to the explicit task identifier, the
   178   client can show these messages in the proper context, e.g.\ a GUI window for
   179   this particular session build job.
   180 
   181   \medskip Subsequently, the protocol message formats are described in further
   182   detail.
   183 \<close>
   184 
   185 
   186 subsection \<open>Byte messages\<close>
   187 
   188 text \<open>
   189   The client-server connection is a raw byte-channel for bidirectional
   190   communication, but the Isabelle server always works with messages of a
   191   particular length. Messages are written as a single chunk that is flushed
   192   immediately.
   193 
   194   Message boundaries are determined as follows:
   195 
   196     \<^item> A \<^emph>\<open>short message\<close> consists of a single line: it is a sequence of
   197     arbitrary bytes excluding CR (13) and LF (10), and terminated by CR-LF or
   198     just LF.
   199 
   200     \<^item> A \<^emph>\<open>long message\<close> starts with a single that consists only of decimal
   201     digits: these are interpreted as length of the subsequent block of
   202     arbitrary bytes. A final line-terminator (as above) may be included here,
   203     but is not required.
   204 
   205   Messages in JSON format (see below) always fit on a single line, due to
   206   escaping of newline characters within string literals. This is convenient
   207   for interactive experimentation, but it can impact performance for very long
   208   messages. If the message byte-length is given on the preceding line, the
   209   server can read the message more efficiently as a single block.
   210 \<close>
   211 
   212 
   213 subsection \<open>Text messages\<close>
   214 
   215 text \<open>
   216   Messages are read and written as byte streams (with byte lengths), but the
   217   content is always interpreted as plain text in terms of the UTF-8
   218   encoding.\<^footnote>\<open>See also the ``UTF-8 Everywhere Manifesto''
   219   \<^url>\<open>http://utf8everywhere.org\<close>.\<close>
   220 
   221   Note that line-endings and other formatting characters are invariant wrt.
   222   UTF-8 representation of text: thus implementations are free to determine the
   223   overall message structure before or after applying the text encoding.
   224 \<close>
   225 
   226 
   227 subsection \<open>Input and output messages \label{sec:input-output-messages}\<close>
   228 
   229 text \<open>
   230   Server input and output messages have a uniform format as follows:
   231 
   232     \<^item> \<open>name argument\<close> such that:
   233 
   234     \<^item> \<open>name\<close> is the longest prefix consisting of ASCII letters, digits,
   235     ``\<^verbatim>\<open>_\<close>'', ``\<^verbatim>\<open>.\<close>'',
   236 
   237     \<^item> the separator between \<open>name\<close> and \<open>argument\<close> is the longest possible
   238     sequence of ASCII blanks (it could be empty, e.g.\ when the argument
   239     starts with a quote or bracket),
   240 
   241     \<^item> \<open>argument\<close> is the rest of the message without line terminator.
   242 
   243   \<^medskip>
   244   Input messages are sent from the client to the server. Here the \<open>name\<close>
   245   specifies a \<^emph>\<open>server command\<close>: the list of known commands may be
   246   retrieved via the \<^verbatim>\<open>help\<close> command.
   247 
   248   \<^medskip>
   249   Output messages are sent from the server to the client. Here the \<open>name\<close>
   250   specifies the \<^emph>\<open>server reply\<close>, which always has a specific meaning as
   251   follows:
   252 
   253     \<^item> synchronous results: \<^verbatim>\<open>OK\<close> or \<^verbatim>\<open>ERROR\<close>
   254     \<^item> asynchronous results: \<^verbatim>\<open>FINISHED\<close> or \<^verbatim>\<open>FAILED\<close>
   255     \<^item> intermediate notifications: \<^verbatim>\<open>NOTE\<close>
   256 
   257   \<^medskip>
   258   The \<open>argument\<close> format is uniform for both input and output messages:
   259 
   260     \<^item> empty argument (Scala type \<^verbatim>\<open>Unit\<close>)
   261     \<^item> XML element in YXML notation (Scala type \<^verbatim>\<open>XML.Elem\<close>)
   262     \<^item> JSON value (Scala type \<^verbatim>\<open>JSON.T\<close>)
   263 
   264   JSON values may consist of objects (records), arrays (lists), strings,
   265   numbers, bools, null.\<^footnote>\<open>See also the official specification
   266   \<^url>\<open>https://www.json.org\<close> and unofficial explorations ``Parsing JSON is a
   267   Minefield'' \<^url>\<open>http://seriot.ch/parsing_json.php\<close>.\<close> Since JSON requires
   268   explicit quotes and backslash-escapes to represent arbitrary text, the YXML
   269   notation for XML trees (\secref{sec:yxml-vs-xml}) works better
   270   for large messages with a lot of PIDE markup.
   271 
   272   Nonetheless, the most common commands use JSON by default: big chunks of
   273   text (theory sources etc.) are taken from the underlying file-system and
   274   results are pre-formatted for plain-text output, without PIDE markup
   275   information. This is a concession to simplicity: the server imitates the
   276   appearance of command-line tools on top of the Isabelle/PIDE infrastructure.
   277 \<close>
   278 
   279 
   280 subsection \<open>Initial password exchange\<close>
   281 
   282 text \<open>
   283   Whenever a new client opens the server socket, the initial message needs to
   284   be its unique password. The server replies either with \<^verbatim>\<open>OK\<close> (and some
   285   information about the Isabelle version) or by silent disconnection of what
   286   is considered an illegal connection attempt. Note that @{tool client}
   287   already presents the correct password internally.
   288 
   289   Server passwords are created as Universally Unique Identifier (UUID) in
   290   Isabelle/Scala and stored in a per-user database, with restricted
   291   file-system access only for the current user. The Isabelle/Scala server
   292   implementation is careful to expose the password only on private output
   293   channels, and not on a process command-line (which is accessible to other
   294   users, e.g.\ via the \<^verbatim>\<open>ps\<close> command).
   295 \<close>
   296 
   297 
   298 subsection \<open>Synchronous commands\<close>
   299 
   300 text \<open>
   301   A \<^emph>\<open>synchronous command\<close> corresponds to regular function application in
   302   Isabelle/Scala, with single argument and result (regular or error). Both the
   303   argument and the result may consist of type \<^verbatim>\<open>Unit\<close>, \<^verbatim>\<open>XML.Elem\<close>, \<^verbatim>\<open>JSON.T\<close>.
   304   An error result typically consists of a JSON object with error message and
   305   potentially further result fields (this resembles exceptions in Scala).
   306 
   307   These are the protocol exchanges for both cases of command execution:
   308   \begin{center}
   309   \begin{tabular}{rl}
   310   \<^bold>\<open>input:\<close> & \<open>command argument\<close> \\
   311   (a) regular \<^bold>\<open>output:\<close> & \<^verbatim>\<open>OK\<close> \<open>result\<close> \\
   312   (b) error \<^bold>\<open>output:\<close> & \<^verbatim>\<open>ERROR\<close> \<open>result\<close> \\
   313   \end{tabular}
   314   \end{center}
   315 \<close>
   316 
   317 
   318 subsection \<open>Asynchronous commands\<close>
   319 
   320 text \<open>
   321   An \<^emph>\<open>asynchronous command\<close> corresponds to an ongoing process that finishes
   322   or fails eventually, while emitting arbitrary notifications in between.
   323   Formally, it starts as synchronous command with immediate result \<^verbatim>\<open>OK\<close>
   324   giving the \<^verbatim>\<open>task\<close> identifier, or an immediate \<^verbatim>\<open>ERROR\<close> that indicates bad
   325   command syntax. For a running task, the termination is indicated later by
   326   \<^verbatim>\<open>FINISHED\<close> or \<^verbatim>\<open>FAILED\<close>, together with its ultimate result value.
   327 
   328   These are the protocol exchanges for various cases of command task
   329   execution:
   330 
   331   \begin{center}
   332   \begin{tabular}{rl}
   333   \<^bold>\<open>input:\<close> & \<open>command argument\<close> \\
   334   immediate \<^bold>\<open>output:\<close> & \<^verbatim>\<open>OK {"task":\<close>\<open>id\<close>\<^verbatim>\<open>}\<close> \\
   335   intermediate \<^bold>\<open>output:\<close> & \<^verbatim>\<open>NOTE {"task":\<close>\<open>id\<close>\<^verbatim>\<open>,\<close>\<open>\<dots>\<close>\<^verbatim>\<open>}\<close> \\
   336   (a) regular \<^bold>\<open>output:\<close> & \<^verbatim>\<open>FINISHED {"task":\<close>\<open>id\<close>\<^verbatim>\<open>,\<close>\<open>\<dots>\<close>\<^verbatim>\<open>}\<close> \\
   337   (b) error \<^bold>\<open>output:\<close> & \<^verbatim>\<open>FAILED {"task":\<close>\<open>id\<close>\<^verbatim>\<open>,\<close>\<open>\<dots>\<close>\<^verbatim>\<open>}\<close> \\[3ex]
   338   \<^bold>\<open>input:\<close> & \<open>command argument\<close> \\
   339   immediate \<^bold>\<open>output:\<close> & \<^verbatim>\<open>ERROR\<close>~\<open>\<dots>\<close> \\
   340   \end{tabular}
   341   \end{center}
   342 
   343   All asynchronous messages are decorated with the task identifier that was
   344   revealed in the immediate (synchronous) result. Thus the client can
   345   invoke further asynchronous commands and still dispatch the resulting stream of
   346   asynchronous messages properly.
   347 
   348   The synchronous command \<^verbatim>\<open>cancel {"task":\<close>~\<open>id\<close>\<^verbatim>\<open>}\<close> tells the specified task
   349   to terminate prematurely: usually causing a \<^verbatim>\<open>FAILED\<close> result, but this is
   350   not guaranteed: the cancel event may come too late or the running process
   351   may just ignore it.
   352 \<close>
   353 
   354 
   355 section \<open>Types for JSON values \label{sec:json-types}\<close>
   356 
   357 text \<open>
   358   In order to specify concrete JSON types for command arguments and result
   359   messages, the following type definition language shall be used:
   360 
   361   \<^rail>\<open>
   362     @{syntax type_def}: @'type' @{syntax name} '=' @{syntax type}
   363     ;
   364     @{syntax type}: @{syntax name} | @{syntax value} | 'any' | 'null' |
   365       'bool' | 'int' | 'long' | 'double' | 'string' | '[' @{syntax type} ']' |
   366       '{' (@{syntax field_type} ',' *) '}' |
   367       @{syntax type} '\<oplus>' @{syntax type} |
   368       @{syntax type} '|' @{syntax type} |
   369       '(' @{syntax type} ')'
   370     ;
   371     @{syntax field_type}: @{syntax name} ('?'?) ':' @{syntax type}
   372   \<close>
   373 
   374   This is a simplified variation of TypeScript
   375   interfaces.\<^footnote>\<open>\<^url>\<open>https://www.typescriptlang.org/docs/handbook/interfaces.html\<close>\<close>
   376   The meaning of these types is specified wrt. the Isabelle/Scala
   377   implementation as follows.
   378 
   379   \<^item> A \<open>name\<close> refers to a type defined elsewhere. The environment of type
   380   definitions is given informally: put into proper foundational order, it
   381   needs to specify a strongly normalizing system of syntactic abbreviations;
   382   type definitions may not be recursive.
   383 
   384   \<^item> A \<open>value\<close> in JSON notation represents the singleton type of the given
   385   item. For example, the string \<^verbatim>\<open>"error"\<close> can be used as type for a slot that
   386   is guaranteed to contain that constant.
   387 
   388   \<^item> Type \<open>any\<close> is the super type of all other types: it is an untyped slot in
   389   the specification and corresponds to \<^verbatim>\<open>Any\<close> or \<^verbatim>\<open>JSON.T\<close> in Isabelle/Scala.
   390 
   391   \<^item> Type \<open>null\<close> is the type of the improper value \<open>null\<close>; it corresponds to
   392   type \<^verbatim>\<open>Null\<close> in Scala and is normally not used in Isabelle/Scala.\<^footnote>\<open>See also
   393   ``Null References: The Billion Dollar Mistake'' by Tony Hoare
   394   \<^url>\<open>https://www.infoq.com/presentations/Null-References-The-Billion-Dollar-Mistake-Tony-Hoare\<close>.\<close>
   395 
   396   \<^item> Type \<open>bool\<close> is the type of the truth values \<^verbatim>\<open>true\<close> and \<^verbatim>\<open>false\<close>; it
   397   corresponds to \<^verbatim>\<open>Boolean\<close> in Scala.
   398 
   399   \<^item> Types \<open>int\<close>, \<open>long\<close>, \<open>double\<close> are specific versions of the generic
   400   \<open>number\<close> type, corresponding to \<^verbatim>\<open>Int\<close>, \<^verbatim>\<open>Long\<close>, \<^verbatim>\<open>Double\<close> in Scala, but
   401   \<^verbatim>\<open>Long\<close> is limited to 53 bit precision.\<^footnote>\<open>Implementations of JSON typically
   402   standardize \<open>number\<close> to \<^verbatim>\<open>Double\<close>, which can absorb \<^verbatim>\<open>Int\<close> faithfully, but
   403   not all of \<^verbatim>\<open>Long\<close>.\<close>
   404 
   405   \<^item> Type \<open>string\<close> represents Unicode text; it corresponds to type \<^verbatim>\<open>String\<close> in
   406   Scala.
   407 
   408   \<^item> Type \<open>[t]\<close> is the array (or list) type over \<open>t\<close>; it corresponds to
   409   \<^verbatim>\<open>List[t]\<close> in Scala. The list type is co-variant as usual (i.e.\ monotonic
   410   wrt. the subtype relation).
   411 
   412   \<^item> Object types describe the possible content of JSON records, with field
   413   names and types. A question mark after a field name means that it is
   414   optional. In Scala this could refer to an explicit type \<^verbatim>\<open>Option[t]\<close>, e.g.\
   415   \<open>{a: int, b?: string}\<close> corresponding to a Scala case class with arguments
   416   \<^verbatim>\<open>a: Int\<close>, \<^verbatim>\<open>b: Option[String]\<close>.
   417 
   418   Alternatively, optional fields can have a default value. If nothing else is
   419   specified, a standard ``empty value'' is used for each type, i.e.\ \<^verbatim>\<open>0\<close> for
   420   the number types, \<^verbatim>\<open>false\<close> for \<open>bool\<close>, or the empty string, array, object
   421   etc.
   422 
   423   Object types are \<^emph>\<open>permissive\<close> in the sense that only the specified field
   424   names need to conform to the given types, but unspecified fields may be
   425   present as well.
   426 
   427   \<^item> The type expression \<open>t\<^sub>1 \<oplus> t\<^sub>2\<close> only works for two object types with
   428   disjoint field names: it is the concatenation of the respective @{syntax
   429   field_type} specifications taken together. For example: \<open>{task: string} \<oplus>
   430   {ok: bool}\<close> is the equivalent to \<open>{task: string, ok: bool}\<close>.
   431 
   432   \<^item> The type expression \<open>t\<^sub>1 | t\<^sub>2\<close> is the disjoint union of two types, either
   433   one of the two cases may occur.
   434 
   435   \<^item> Parentheses \<open>(t)\<close> merely group type expressions syntactically.
   436 
   437 
   438   These types correspond to JSON values in an obvious manner, which is not
   439   further described here. For example, the JSON array \<^verbatim>\<open>[1, 2, 3]\<close> conforms to
   440   types \<open>[int]\<close>, \<open>[long]\<close>, \<open>[double]\<close>, \<open>[any]\<close>, \<open>any\<close>.
   441 
   442   Note that JSON objects require field names to be quoted, but the type
   443   language omits quotes for clarity. Thus the object \<^verbatim>\<open>{"a": 42, "b": "xyz"}\<close>
   444   conforms to the type \<open>{a: int, b: string}\<close>, for example.
   445 
   446   \<^medskip>
   447   The absence of an argument or result is represented by the Scala type
   448   \<^verbatim>\<open>Unit\<close>: it is written as empty text in the message \<open>argument\<close>
   449   (\secref{sec:input-output-messages}). This is not part of the JSON language.
   450 
   451   Server replies have name tags like \<^verbatim>\<open>OK\<close>, \<^verbatim>\<open>ERROR\<close>: these are used literally
   452   together with type specifications to indicate the particular name with the
   453   type of its argument, e.g.\ \<^verbatim>\<open>OK\<close>~\<open>[string]\<close> for a regular result that is a
   454   list (JSON array) of strings.
   455 
   456   \<^bigskip>
   457   Here are some common type definitions, for use in particular specifications
   458   of command arguments and results.
   459 
   460   \<^item> \<^bold>\<open>type\<close>~\<open>position = {line?: int, offset?: int, end_offset?: int, file?:
   461   string, id?: long}\<close> describes a source position within Isabelle text. Only
   462   the \<open>line\<close> and \<open>file\<close> fields make immediate sense to external programs.
   463   Detailed \<open>offset\<close> and \<open>end_offset\<close> positions are counted according to
   464   Isabelle symbols, see @{ML_type Symbol.symbol} in Isabelle/ML @{cite
   465   "isabelle-implementation"}. The position \<open>id\<close> belongs to the representation
   466   of command transactions in the Isabelle/PIDE protocol: it normally does not
   467   occur in externalized positions.
   468 
   469   \<^item> \<^bold>\<open>type\<close>~\<open>message = {kind: string, message: string, pos?: position}\<close> where
   470   the \<open>kind\<close> provides some hint about the role and importance of the message.
   471   The main message kinds are \<^verbatim>\<open>writeln\<close> (for regular output), \<^verbatim>\<open>warning\<close>,
   472   \<^verbatim>\<open>error\<close>.
   473 
   474   \<^item> \<^bold>\<open>type\<close>~\<open>error_message = {kind:\<close>~\<^verbatim>\<open>"error"\<close>\<open>, message: string}\<close> refers to
   475   error messages in particular. These occur routinely with \<^verbatim>\<open>ERROR\<close> or
   476   \<^verbatim>\<open>FAILED\<close> replies, but also as initial command syntax errors (which are
   477   omitted in the command specifications below).
   478 
   479   \<^item> \<^bold>\<open>type\<close>~\<open>theory_progress = {kind:\<close>~\<^verbatim>\<open>"writeln"\<close>\<open>, message: string, theory:
   480   string, session: string}\<close> reports formal progress in loading theories (e.g.\
   481   when building a session image). Apart from a regular output message, it also
   482   reveals the formal theory name (e.g.\ \<^verbatim>\<open>"HOL.Nat"\<close>) and session name (e.g.\
   483   \<^verbatim>\<open>"HOL"\<close>). Note that some rare theory names lack a proper session prefix,
   484   e.g. theory \<^verbatim>\<open>"Main"\<close> in session \<^verbatim>\<open>"HOL"\<close>.
   485 
   486   \<^item> \<^bold>\<open>type\<close>~\<open>timing = {elapsed: double, cpu: double, gc: double}\<close> refers to
   487   common Isabelle timing information in seconds, usually with a precision of
   488   three digits after the point (whole milliseconds).
   489 
   490   \<^item> \<^bold>\<open>type\<close>~\<open>uuid = string\<close> refers to a Universally Unique Identifier (UUID)
   491   as plain text.\<^footnote>\<open>See \<^url>\<open>https://www.ietf.org/rfc/rfc4122.txt\<close> and
   492   \<^url>\<open>https://docs.oracle.com/javase/8/docs/api/java/util/UUID.html\<close>.\<close> Such
   493   identifiers are created as private random numbers of the server and only
   494   revealed to the client that creates a certain resource (e.g.\ task or
   495   session). A client may disclose this information for use in a different
   496   client connection: this allows to share sessions between multiple
   497   connections.
   498 
   499   Client commands need to provide syntactically wellformed UUIDs: this is
   500   trivial to achieve by using only identifiers that have been produced by the
   501   server beforehand.
   502 
   503   \<^item> \<^bold>\<open>type\<close>~\<open>task = {task: uuid}\<close> identifies a newly created asynchronous task
   504   and thus allows the client to control it by the \<^verbatim>\<open>cancel\<close> command. The same
   505   task identification is included in all messages produced by this task.
   506 
   507   \<^item> \<^bold>\<open>type\<close> \<open>session_id = {session_id: uuid}\<close> identifies a newly created PIDE
   508   session managed by the server. Sessions are independent of client
   509   connections and may be shared by different clients, as long as the internal
   510   session identifier is known.
   511 
   512   \<^item> \<^bold>\<open>type\<close> \<open>node_status = {ok: bool, total: int, unprocessed: int, running:
   513   int, warned: int, failed: int, finished: int, consolidated: bool}\<close>
   514   represents a formal theory node status of the PIDE document model. Fields
   515   \<open>total\<close>, \<open>unprocessed\<close>, \<open>running\<close>, \<open>warned\<close>, \<open>failed\<close>, \<open>finished\<close> account
   516   for individual commands within a theory node; \<open>ok\<close> is an abstraction for
   517   \<open>failed = 0\<close>. The \<open>consolidated\<close> flag indicates whether the outermost theory
   518   command structure has finished (or failed) and the final \<^theory_text>\<open>end\<close> command has
   519   been checked.
   520 \<close>
   521 
   522 
   523 section \<open>Server commands and results\<close>
   524 
   525 text \<open>
   526   Here follows an overview of particular Isabelle server commands with their
   527   results, which are usually represented as JSON values with types according
   528   to \secref{sec:json-types}. The general format of input and output messages
   529   is described in \secref{sec:input-output-messages}. The relevant
   530   Isabelle/Scala source files are:
   531 
   532   \<^medskip>
   533   \begin{tabular}{l}
   534   \<^file>\<open>$ISABELLE_HOME/src/Pure/Tools/server_commands.scala\<close> \\
   535   \<^file>\<open>$ISABELLE_HOME/src/Pure/Tools/server.scala\<close> \\
   536   \<^file>\<open>$ISABELLE_HOME/src/Pure/General/json.scala\<close> \\
   537   \end{tabular}
   538 \<close>
   539 
   540 
   541 subsection \<open>Command \<^verbatim>\<open>help\<close>\<close>
   542 
   543 text \<open>
   544   \begin{tabular}{ll}
   545   regular result: & \<^verbatim>\<open>OK\<close> \<open>[string]\<close> \\
   546   \end{tabular}
   547   \<^medskip>
   548 
   549   The \<^verbatim>\<open>help\<close> command has no argument and returns the list of server command
   550   names. This is occasionally useful for interactive experimentation (see also
   551   @{tool client} in \secref{sec:tool-client}).
   552 \<close>
   553 
   554 
   555 subsection \<open>Command \<^verbatim>\<open>echo\<close>\<close>
   556 
   557 text \<open>
   558   \begin{tabular}{ll}
   559   argument: & \<open>any\<close> \\
   560   regular result: & \<^verbatim>\<open>OK\<close> \<open>any\<close> \\
   561   \end{tabular}
   562   \<^medskip>
   563 
   564   The \<^verbatim>\<open>echo\<close> command is the identity function: it returns its argument as
   565   regular result. This is occasionally useful for testing and interactive
   566   experimentation (see also @{tool client} in \secref{sec:tool-client}).
   567 
   568   The Scala type of \<^verbatim>\<open>echo\<close> is actually more general than given above:
   569   \<^verbatim>\<open>Unit\<close>, \<^verbatim>\<open>XML.Elem\<close>, \<^verbatim>\<open>JSON.T\<close> work uniformly. Note that \<^verbatim>\<open>XML.Elem\<close> might
   570   be difficult to type on the console in its YXML syntax
   571   (\secref{sec:yxml-vs-xml}).
   572 \<close>
   573 
   574 
   575 subsection \<open>Command \<^verbatim>\<open>shutdown\<close>\<close>
   576 
   577 text \<open>
   578   \begin{tabular}{ll}
   579   regular result: & \<^verbatim>\<open>OK\<close> \\
   580   \end{tabular}
   581   \<^medskip>
   582 
   583   The \<^verbatim>\<open>shutdown\<close> command has no argument and result value. It forces a
   584   shutdown of the connected server process, stopping all open sessions and
   585   closing the server socket. This may disrupt pending commands on other
   586   connections!
   587 
   588   \<^medskip>
   589   The command-line invocation \<^verbatim>\<open>isabelle server -x\<close> opens a server connection
   590   and issues a \<^verbatim>\<open>shutdown\<close> command (see also \secref{sec:tool-server}).
   591 \<close>
   592 
   593 
   594 subsection \<open>Command \<^verbatim>\<open>cancel\<close>\<close>
   595 
   596 text \<open>
   597   \begin{tabular}{ll}
   598   argument: & \<open>task\<close> \\
   599   regular result: & \<^verbatim>\<open>OK\<close> \\
   600   \end{tabular}
   601   \<^medskip>
   602 
   603   The command \<^verbatim>\<open>cancel {"task":\<close>~\<open>id\<close>\<^verbatim>\<open>}\<close> attempts to cancel the specified
   604   task.
   605 
   606   Cancellation is merely a hint that the client prefers an ongoing process to
   607   be stopped. The command always succeeds formally, but it may get ignored by
   608   a task that is still running; it might also refer to a non-existing or
   609   no-longer existing task (without producing an error).
   610 
   611   Successful cancellation typically leads to an asynchronous failure of type
   612   \<^verbatim>\<open>FAILED {\<close>\<open>task: uuid, message:\<close>~\<^verbatim>\<open>"Interrupt"}\<close>. A different message is
   613   also possible, depending how the task handles the event.
   614 \<close>
   615 
   616 
   617 subsection \<open>Command \<^verbatim>\<open>session_build\<close> \label{sec:command-session-build}\<close>
   618 
   619 text \<open>
   620   \begin{tabular}{lll}
   621   argument: & \<open>session_build_args\<close> \\
   622   immediate result: & \<^verbatim>\<open>OK\<close> \<open>task\<close> \\
   623   notifications: & \<^verbatim>\<open>NOTE\<close> \<open>task \<oplus> (theory_progress | message)\<close> \\
   624   regular result: & \<^verbatim>\<open>FINISHED\<close> \<open>task \<oplus> session_build_results\<close> \\
   625   error result: & \<^verbatim>\<open>FAILED\<close> \<open>task \<oplus> error_message \<oplus> session_build_results\<close> \\[2ex]
   626   \end{tabular}
   627 
   628   \begin{tabular}{lll}
   629   \<^bold>\<open>type\<close> \<open>session_build_args =\<close> \\
   630   \quad\<open>{session: string,\<close> \\
   631   \quad~~\<open>preferences?: string,\<close> & \<^bold>\<open>default:\<close> server preferences \\
   632   \quad~~\<open>options?: [string],\<close> \\
   633   \quad~~\<open>dirs?: [string],\<close> \\
   634   \quad~~\<open>include_sessions: [string],\<close> \\
   635   \quad~~\<open>system_mode?: bool,\<close> \\
   636   \quad~~\<open>verbose?: bool}\<close> \\[2ex]
   637   \end{tabular}
   638 
   639   \begin{tabular}{ll}
   640   \<^bold>\<open>type\<close> \<open>session_build_result =\<close> \\
   641   \quad\<open>{session: string,\<close> \\
   642   \quad~~\<open>ok: bool,\<close> \\
   643   \quad~~\<open>return_code: int,\<close> \\
   644   \quad~~\<open>timeout: bool,\<close> \\
   645   \quad~~\<open>timing: timing}\<close> \\[2ex]
   646 
   647   \<^bold>\<open>type\<close> \<open>session_build_results =\<close> \\
   648   \quad\<open>{ok: bool,\<close> \\
   649   \quad~~\<open>return_code: int,\<close> \\
   650   \quad~~\<open>sessions: [session_build_result]}\<close> \\
   651   \end{tabular}
   652 \<close>
   653 
   654 text \<open>
   655   The \<^verbatim>\<open>session_build\<close> command prepares a session image for interactive use of
   656   theories. This is a limited version of command-line tool @{tool build}
   657   (\secref{sec:tool-build}), with specific options to request a formal context
   658   for an interactive PIDE session.
   659 
   660   The build process is asynchronous, with notifications that inform about the
   661   progress of loaded theories. Some further informative messages are output as
   662   well.
   663 
   664   Coordination of independent build processes is at the discretion of the
   665   client (or end-user), just as for @{tool build} and @{tool jedit}. There is
   666   no built-in coordination of conflicting builds with overlapping hierarchies
   667   of session images. In the worst case, a session image produced by one task
   668   may get overwritten by another task!
   669 \<close>
   670 
   671 
   672 subsubsection \<open>Arguments\<close>
   673 
   674 text \<open>
   675   The \<open>session\<close> field specifies the target session name. The build process
   676   will produce all required ancestor images according to the overall session
   677   graph.
   678 
   679   \<^medskip>
   680   The environment of Isabelle system options is determined from \<open>preferences\<close>
   681   that are augmented by \<open>options\<close>, which is a list individual updates of the
   682   form the \<open>name\<close>\<^verbatim>\<open>=\<close>\<open>value\<close> or \<open>name\<close> (the latter abbreviates
   683   \<open>name\<close>\<^verbatim>\<open>=true\<close>); see also command-line option \<^verbatim>\<open>-o\<close> for @{tool build}. The
   684   preferences are loaded from the file
   685   \<^path>\<open>$ISABELLE_HOME_USER/etc/preferences\<close> by default, but the client may
   686   provide alternative contents for it (as text, not a file-name). This could
   687   be relevant in situations where client and server run in different
   688   operating-system contexts.
   689 
   690   \<^medskip>
   691   The \<open>dirs\<close> field specifies additional directories for session ROOT and ROOTS
   692   files (\secref{sec:session-root}). This augments the name space of available
   693   sessions; see also option \<^verbatim>\<open>-d\<close> in @{tool build}.
   694 
   695   \<^medskip>
   696   The \<open>include_sessions\<close> field specifies sessions whose theories should be
   697   included in the overall name space of session-qualified theory names. This
   698   corresponds to a \<^bold>\<open>sessions\<close> specification in ROOT files
   699   (\secref{sec:session-root}). It enables the \<^verbatim>\<open>use_theories\<close> command
   700   (\secref{sec:command-use-theories}) to refer to sources from other sessions
   701   in a robust manner, instead of relying on directory locations.
   702 
   703   \<^medskip>
   704   The \<open>system_mode\<close> field set to \<^verbatim>\<open>true\<close> stores resulting session images and
   705   log files in @{path "$ISABELLE_HOME/heaps"} instead of the default location
   706   @{setting ISABELLE_OUTPUT} (which is normally in @{setting
   707   ISABELLE_HOME_USER}). See also option \<^verbatim>\<open>-s\<close> in @{tool build}.
   708 
   709   \<^medskip>
   710   The \<open>verbose\<close> field set to \<^verbatim>\<open>true\<close> yields extra verbosity. The effect is
   711   similar to option \<^verbatim>\<open>-v\<close> in @{tool build}.
   712 \<close>
   713 
   714 
   715 subsubsection \<open>Intermediate output\<close>
   716 
   717 text \<open>
   718   The asynchronous notifications of command \<^verbatim>\<open>session_build\<close> mainly serve as
   719   progress indicator: the output resembles that of the session build window of
   720   Isabelle/jEdit after startup @{cite "isabelle-jedit"}.
   721 
   722   For the client it is usually sufficient to print the messages in plain text,
   723   but note that \<open>theory_progress\<close> also reveals formal \<open>theory\<close> and
   724   \<open>session\<close> names directly.
   725 \<close>
   726 
   727 
   728 subsubsection \<open>Results\<close>
   729 
   730 text \<open>
   731   The overall \<open>session_build_results\<close> contain both a summary and an entry
   732   \<open>session_build_result\<close> for each session in the build hierarchy. The result
   733   is always provided, independently of overall success (\<^verbatim>\<open>FINISHED\<close> task) or
   734   failure (\<^verbatim>\<open>FAILED\<close> task).
   735 
   736   The \<open>ok\<close> field tells abstractly, whether all required session builds came
   737   out as \<open>ok\<close>, i.e.\ with zero \<open>return_code\<close>. A non-zero \<open>return_code\<close>
   738   indicates an error according to usual POSIX conventions for process exit.
   739 
   740   The individual \<open>session_build_result\<close> entries provide extra fields:
   741 
   742   \<^item> \<open>timeout\<close> tells if the build process was aborted after running too long,
   743 
   744   \<^item> \<open>timing\<close> gives the overall process timing in the usual Isabelle format
   745   with elapsed, CPU, GC time.
   746 \<close>
   747 
   748 
   749 subsubsection \<open>Examples\<close>
   750 
   751 text \<open>
   752   Build of a session image from the Isabelle distribution:
   753   @{verbatim [display] \<open>session_build {"session": "HOL-Word"}\<close>}
   754 
   755   Build a session image from the Archive of Formal Proofs:
   756   @{verbatim [display] \<open>session_build {"session": "Coinductive", "dirs": ["$AFP_BASE/thys"]}\<close>}
   757 \<close>
   758 
   759 
   760 subsection \<open>Command \<^verbatim>\<open>session_start\<close> \label{sec:command-session-start}\<close>
   761 
   762 text \<open>
   763   \begin{tabular}{lll}
   764   argument: & \<open>session_build_args \<oplus> {print_mode?: [string]}\<close> \\
   765   immediate result: & \<^verbatim>\<open>OK\<close> \<open>task\<close> \\
   766   notifications: & \<^verbatim>\<open>NOTE\<close> \<open>task \<oplus> (theory_progress | message)\<close> \\
   767   regular result: & \<^verbatim>\<open>FINISHED\<close> \<open>task \<oplus> session_id \<oplus> {tmp_dir: string}\<close> \\
   768   error result: & \<^verbatim>\<open>FAILED\<close> \<open>task \<oplus> error_message\<close> \\[2ex]
   769   \end{tabular}
   770 
   771   \<^medskip>
   772   The \<^verbatim>\<open>session_start\<close> command starts a new Isabelle/PIDE session with
   773   underlying Isabelle/ML process, based on a session image that it produces on
   774   demand using \<^verbatim>\<open>session_build\<close>. Thus it accepts all \<open>session_build_args\<close> and
   775   produces similar notifications, but the detailed \<open>session_build_results\<close> are
   776   omitted.
   777 
   778   The session build and startup process is asynchronous: when the task is
   779   finished, the session remains active for commands, until a \<^verbatim>\<open>session_stop\<close>
   780   or \<^verbatim>\<open>shutdown\<close> command is sent to the server.
   781 
   782   Sessions are independent of client connections: it is possible to start a
   783   session and later apply \<^verbatim>\<open>use_theories\<close> on different connections, as long as
   784   the internal session identifier is known: shared theory imports will be used
   785   only once (and persist until purged explicitly).
   786 \<close>
   787 
   788 
   789 subsubsection \<open>Arguments\<close>
   790 
   791 text \<open>
   792   Most arguments are shared with \<^verbatim>\<open>session_build\<close>
   793   (\secref{sec:command-session-build}).
   794 
   795   \<^medskip>
   796   The \<open>print_mode\<close> field adds identifiers of print modes to be made active for
   797   this session. For example, \<^verbatim>\<open>"print_mode": ["ASCII"]\<close> prefers ASCII
   798   replacement syntax over mathematical Isabelle symbols. See also option \<^verbatim>\<open>-m\<close>
   799   in @{tool process} (\secref{sec:tool-process}).
   800 \<close>
   801 
   802 
   803 subsubsection \<open>Results\<close>
   804 
   805 text \<open>
   806   The \<open>session_id\<close> provides the internal identification of the session object
   807   within the sever process. It can remain active as long as the server is
   808   running, independently of the current client connection.
   809 
   810   \<^medskip>
   811   The \<open>tmp_dir\<close> fields reveals a temporary directory that is specifically
   812   created for this session and deleted after it has been stopped. This may
   813   serve as auxiliary file-space for the \<^verbatim>\<open>use_theories\<close> command, but
   814   concurrent use requires some care in naming temporary files, e.g.\ by
   815   using sub-directories with globally unique names.
   816 \<close>
   817 
   818 
   819 subsection \<open>Examples\<close>
   820 
   821 text \<open>
   822   Start a default Isabelle/HOL session:
   823   @{verbatim [display] \<open>session_start {"session": "HOL"}\<close>}
   824 
   825   Start a session from the Archive of Formal Proofs:
   826   @{verbatim [display] \<open>session_start {"session": "Coinductive", "dirs": ["$AFP_BASE/thys"]}\<close>}
   827 \<close>
   828 
   829 
   830 subsection \<open>Command \<^verbatim>\<open>session_stop\<close>\<close>
   831 
   832 text \<open>
   833   \begin{tabular}{ll}
   834   argument: & \<open>session_id\<close> \\
   835   immediate result: & \<^verbatim>\<open>OK\<close> \<open>task\<close> \\
   836   regular result: & \<^verbatim>\<open>FINISHED\<close> \<open>task \<oplus> session_stop_result\<close> \\
   837   error result: & \<^verbatim>\<open>FAILED\<close> \<open>task \<oplus> error_message \<oplus> session_stop_result\<close> \\[2ex]
   838   \end{tabular}
   839 
   840   \begin{tabular}{l}
   841   \<^bold>\<open>type\<close> \<open>session_stop_result = {ok: bool, return_code: int}\<close>
   842   \end{tabular}
   843 
   844   \<^medskip>
   845   The \<^verbatim>\<open>session_stop\<close> command forces a shutdown of the identified PIDE
   846   session. This asynchronous tasks usually finishes quickly. Failure only
   847   happens in unusual situations, according to the return code of the
   848   underlying Isabelle/ML process.
   849 \<close>
   850 
   851 
   852 subsubsection \<open>Arguments\<close>
   853 
   854 text \<open>
   855   The \<open>session_id\<close> provides the UUID originally created by the server for this
   856   session.
   857 \<close>
   858 
   859 
   860 subsubsection \<open>Results\<close>
   861 
   862 text \<open>
   863   The \<open>ok\<close> field tells abstractly, whether the Isabelle/ML process has
   864   terminated properly.
   865 
   866   The \<open>return_code\<close> field expresses this information according to usual POSIX
   867   conventions for process exit.
   868 \<close>
   869 
   870 
   871 subsection \<open>Command \<^verbatim>\<open>use_theories\<close> \label{sec:command-use-theories}\<close>
   872 
   873 text \<open>
   874   \begin{tabular}{ll}
   875   argument: & \<open>use_theories_arguments\<close> \\
   876   regular result: & \<^verbatim>\<open>OK\<close> \<open>use_theories_results\<close> \\
   877   \end{tabular}
   878 
   879   \begin{tabular}{ll}
   880   \<^bold>\<open>type\<close> \<open>use_theories_arguments =\<close> \\
   881   \quad\<open>{session_id: uuid,\<close> \\
   882   \quad~~\<open>theories: [string],\<close> \\
   883   \quad~~\<open>master_dir?: string,\<close> \\
   884   \quad~~\<open>pretty_margin?: double\<close> & \<^bold>\<open>default:\<close> \<^verbatim>\<open>76\<close> \\
   885   \quad~~\<open>unicode_symbols?: bool}\<close> \\[2ex]
   886   \end{tabular}
   887 
   888   \begin{tabular}{ll}
   889   \<^bold>\<open>type\<close> \<open>node_result =\<close> \\
   890   \quad\<open>{node_name: string,\<close> \\
   891   \quad~~\<open>theory: string,\<close> \\
   892   \quad~~\<open>status: node_status,\<close> \\
   893   \quad~~\<open>messages: [message]}\<close> \\[2ex]
   894 
   895   \<^bold>\<open>type\<close> \<open>use_theories_results =\<close> \\
   896   \quad\<open>{ok: bool,\<close> \\
   897   \quad~~\<open>errors: [message],\<close> \\
   898   \quad~~\<open>nodes: [node_result]}\<close> \\[2ex]
   899   \end{tabular}
   900 
   901   \<^medskip>
   902   The \<^verbatim>\<open>use_theories\<close> command updates the identified session by adding the
   903   current version of theory files to it, while dependencies are resolved
   904   implicitly. The command succeeds eventually, when all theories have been
   905   \<^emph>\<open>consolidated\<close> in the sense the formal \<open>node_status\<close>
   906   (\secref{sec:json-types}): the outermost command structure has finished (or
   907   failed) and the final \<^theory_text>\<open>end\<close> command of each theory has been checked.
   908 
   909   Already used theories persist in the session until purged explicitly. This
   910   also means that repeated invocations of \<^verbatim>\<open>use_theories\<close> are idempotent: it
   911   could make sense to do that with different values for \<open>pretty_margin\<close> or
   912   \<open>unicode_symbols\<close> to get different formatting for \<open>errors\<close> or \<open>messages\<close>.
   913 \<close>
   914 
   915 
   916 subsubsection \<open>Arguments\<close>
   917 
   918 text \<open>
   919   The \<open>session_id\<close> is the identifier provided by the server, when the session
   920   was created (possibly on a different client connection).
   921 
   922   \<^medskip>
   923   The \<open>theories\<close> field specifies theory names as in theory \<^theory_text>\<open>imports\<close> or in
   924   ROOT \<^bold>\<open>theories\<close>.
   925 
   926   \<^medskip> The \<open>master_dir\<close> field specifies the master directory of imported
   927   theories: it acts like the ``current working directory'' for locating theory
   928   files. This may be omitted if all entries of \<open>theories\<close> use a
   929   session-qualified theory name (e.g.\ \<^verbatim>\<open>"HOL-Library.AList"\<close>) or absolute
   930   path name (e.g.\ \<^verbatim>\<open>"~~/src/HOL/ex/Seq"\<close>).
   931 
   932   \<^medskip>
   933   The \<open>pretty_margin\<close> field specifies the line width for pretty-printing. The
   934   default is suitable for classic console output. Formatting happens at the
   935   end of \<^verbatim>\<open>use_theories\<close>, when all prover messages are exported to the client.
   936 
   937   \<^medskip>
   938   The \<open>unicode_symbols\<close> field set to \<^verbatim>\<open>true\<close> renders message output for direct
   939   output on a Unicode capable channel, ideally with the Isabelle fonts as in
   940   Isabelle/jEdit. The default is to keep the symbolic representation of
   941   Isabelle text, e.g.\ \<^verbatim>\<open>\<forall>\<close> instead of its rendering as \<open>\<forall>\<close>. This means the
   942   client needs to perform its own rendering before presenting it to the
   943   end-user.
   944 \<close>
   945 
   946 
   947 subsubsection \<open>Results\<close>
   948 
   949 text \<open>
   950   The \<open>ok\<close> field indicates overall success of processing the specified
   951   theories with all their dependencies.
   952 
   953   When \<open>ok\<close> is \<^verbatim>\<open>false\<close>, the \<open>errors\<close> field lists all errors cumulatively
   954   (including imported theories). The messages contain position information for
   955   the original theory nodes.
   956 
   957   \<^medskip>
   958   The \<open>nodes\<close> field provides detailed information about each imported theory
   959   node. The individual fields are as follows:
   960 
   961   \<^item> \<open>node_name\<close>: the physical name for the theory node, based on its
   962   file-system location;
   963 
   964   \<^item> \<open>theory\<close>: the logical theory name, e.g.\ \<^verbatim>\<open>HOL-Library.AList\<close>;
   965 
   966   \<^item> \<open>status\<close>: the overall node status, e.g.\ see the visualization in the
   967   \<open>Theories\<close> panel of Isabelle/jEdit @{cite "isabelle-jedit"};
   968 
   969   \<^item> \<open>messages\<close>: the main bulk of prover messages produced in this theory
   970   (with kind \<^verbatim>\<open>writeln\<close>, \<^verbatim>\<open>warning\<close>, \<^verbatim>\<open>error\<close>).
   971 \<close>
   972 
   973 
   974 subsubsection \<open>Examples\<close>
   975 
   976 text \<open>
   977   Process some example theory from the Isabelle distribution, within the
   978   context of an already started session for Isabelle/HOL (see also
   979   \secref{sec:command-session-start}):
   980   @{verbatim [display] \<open>use_theories {"session_id": ..., "theories": ["~~/src/HOL/ex/Seq"]}\<close>}
   981 
   982   \<^medskip>
   983   Process some example theories in the context of their (single) parent
   984   session:
   985 
   986   @{verbatim [display] \<open>session_start {"session": "HOL-Library"}
   987 use_theories {"session_id": ..., "theories": ["~~/src/HOL/Unix/Unix"]}
   988 session_stop {"session_id": ...}\<close>}
   989 
   990   \<^medskip>
   991   Process some example theories that import other theories via
   992   session-qualified theory names:
   993 
   994   @{verbatim [display] \<open>session_start {"session": "HOL", "include_sessions": ["HOL-Unix"]}
   995 use_theories {"session_id": ..., "theories": ["HOL-Unix.Unix"]}
   996 session_stop {"session_id": ...}\<close>}
   997 \<close>
   998 
   999 end