support for Isabelle/Scala in pure Java;

--- a/Admin/lib/Tools/build_setup	Thu Jul 01 23:26:06 2021 +0200
+++ b/Admin/lib/Tools/build_setup	Thu Jul 01 23:27:43 2021 +0200
@@ -7,6 +7,7 @@
 ## sources
 
 declare -a SOURCES=(
+  "Build_Scala.java"
   "Environment.java"
   "Setup.java"
 )

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Tools/Setup/isabelle/setup/Build_Scala.java	Thu Jul 01 23:27:43 2021 +0200
@@ -0,0 +1,203 @@
+/*  Title:      Tools/Setup/isabelle/setup/Build_Scala.java
+    Author:     Makarius
+
+Build Isabelle/Scala modules.
+*/
+
+package isabelle.setup;
+
+
+import java.io.File;
+import java.io.IOException;
+import java.math.BigInteger;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Properties;
+import java.util.stream.Stream;
+
+
+public class Build_Scala
+{
+    public static class Context
+    {
+        private final Path component_dir;
+        private Properties props;
+
+        public Context(Path dir) throws IOException
+        {
+            component_dir = dir;
+            props = new Properties();
+            Path path = component_dir.resolve("etc/scala.props");
+            if (Files.exists(path)) { props.load(Files.newBufferedReader(path)); }
+        }
+
+        @Override public String toString()
+        {
+            return component_dir.toString();
+        }
+
+        public String component_name()
+        {
+            return component_dir.toFile().getName();
+        }
+
+        public String name()
+        {
+            return props.getProperty("name", component_name());
+        }
+
+        public String description()
+        {
+            return props.getProperty("description", name());
+        }
+
+        public String lib_name()
+        {
+            return props.getProperty("lib", "lib") + "/" + name();
+        }
+
+        public String main()
+        {
+            return props.getProperty("main", "");
+        }
+
+        public List<String> sources()
+        {
+            return Arrays.asList(props.getProperty("sources", "").split("\\s+"));
+        }
+
+        public List<String> services()
+        {
+            return Arrays.asList(props.getProperty("services", "").split("\\s+"));
+        }
+
+        public Path path(String file)
+        {
+            return component_dir.resolve(file);
+        }
+
+        public boolean exists(String file)
+        {
+            return Files.exists(path(file));
+        }
+
+        public String shasum(String file)
+            throws IOException, NoSuchAlgorithmException
+        {
+            if (exists(file)) {
+                MessageDigest sha = MessageDigest.getInstance("SHA");
+                sha.update(Files.readAllBytes(path(file)));
+                String digest = new BigInteger(1, sha.digest()).toString(16);
+                return digest + " *" + file + "\n";
+            }
+            else { return ""; }
+        }
+    }
+
+    public static void build_scala(Context context, boolean fresh)
+        throws IOException, InterruptedException, NoSuchAlgorithmException
+    {
+        String jar_name = context.lib_name() + ".jar";
+        String shasum_name = context.lib_name() + ".shasum";
+
+        List<String> sources = context.sources();
+
+        if (sources.isEmpty()) {
+            Files.deleteIfExists(context.path(jar_name));
+            Files.deleteIfExists(context.path(shasum_name));
+        }
+        else {
+            String shasum_old =
+                context.exists(shasum_name) ? Files.readString(context.path(shasum_name)) : "";
+            String shasum_sources;
+            {
+                StringBuilder _shasum = new StringBuilder();
+                for (String s : sources) {
+                    _shasum.append(context.shasum(s));
+                }
+                shasum_sources = _shasum.toString();
+            }
+            if (fresh || !shasum_old.equals(context.shasum(jar_name) + shasum_sources)) {
+                System.out.println("### Building " + context.description() + " ...");
+
+                String java_home = Environment.getenv("JAVA_HOME");
+                String scala_home = Environment.getenv("SCALA_HOME");
+                String scalac_options = Environment.getenv("ISABELLE_SCALAC_OPTIONS");
+                String isabelle_class_path = Environment.getenv("ISABELLE_CLASSPATH");
+
+                if (java_home.isEmpty()) {
+                    throw new RuntimeException("Unknown JAVA_HOME -- Java unavailable");
+                }
+                if (scala_home.isEmpty()) {
+                    throw new RuntimeException("Unknown SCALA_HOME -- Scala unavailable");
+                }
+
+                Path build_dir = Files.createTempDirectory("isabelle");
+                try {
+                    /* classpath */
+
+                    List<String> classpath = new LinkedList<String>();
+                    for (String s : isabelle_class_path.split(":", -1)) {
+                        classpath.add(Environment.platform_path(s));
+                    }
+
+                    Map<String,String> env = new HashMap<String,String>(Environment.settings());
+                    env.put("CLASSPATH", String.join(File.pathSeparator, classpath));
+
+
+                    /* scalac */
+
+                    List<String> cmd = new LinkedList<String>();
+                    Environment.Exec_Result res;
+
+                    cmd.add(Environment.platform_path(scala_home + "/bin/scalac"));
+                    for (String s : scalac_options.split("\\s+")) { cmd.add(s); }
+                    cmd.add("-d");
+                    cmd.add(build_dir.toString());
+                    for (String s : sources) { cmd.add(context.path(s).toString()); }
+
+                    res = Environment.exec_process(cmd, build_dir.toFile(), env, false);
+                    if (!res.ok()) throw new RuntimeException(res.err());
+
+
+                    /* jar */
+
+                    cmd.clear();
+                    cmd.add(Environment.platform_path(java_home + "/bin/jar"));
+                    cmd.add("-c");
+                    cmd.add("-f");
+                    cmd.add(context.path(jar_name).toString());
+                    if (!context.main().isEmpty()) {
+                        cmd.add("-e");
+                        cmd.add(context.main());
+                    }
+                    cmd.add(".");
+
+                    res = Environment.exec_process(cmd, build_dir.toFile(), env, false);
+                    if (!res.ok()) throw new RuntimeException(res.err());
+
+
+                    /* shasum */
+
+                    String shasum = context.shasum(jar_name) + shasum_sources;
+                    Files.writeString(context.path(shasum_name), shasum);
+                }
+                finally {
+                    try (Stream<Path> walk = Files.walk(build_dir)) {
+                        walk.sorted(Comparator.reverseOrder())
+                            .map(Path::toFile)
+                            .forEach(File::delete);
+                    }
+                }
+            }
+        }
+    }
+}