# Isabelle Prover IDE support
This extension connects VSCode to the Isabelle Prover IDE infrastructure: it
requires a suitable repository version of Isabelle.
The implementation is centered around the VSCode Language Server protocol, but
with many add-ons that are specific to VSCode and Isabelle/PIDE.
See also:
* <https://isabelle.sketis.net/repos/isabelle/file/tip/src/Tools/VSCode>
* <https://github.com/Microsoft/language-server-protocol>
## Screenshot
![[Isabelle/VSCode]](https://isabelle.in.tum.de/repos/isabelle/raw-file/b565a39627bb/src/Tools/VSCode/extension/isabelle_vscode.png)
## Notable Features
* Static syntax tables for Isabelle `.thy` and `.ML` files.
* Implicit dependency management of sources, subject to changes of theory
files within the editor, as well as external file-system events.
* Implicit formal checking of theory files, using the *cursor position* of the
active editor panel as indication for relevant spots.
* Text overview lane with formal status of prover commands (unprocessed,
running, error, warning).
* Prover messages within the source text (errors/warnings and information
messages).
* Semantic text decorations: colors for free/bound variables, inferred types
etc.
* Visual indication of formal scopes and hyperlinks for formal entities.
* Implicit proof state output via the VSCode message channel "Isabelle
Output".
* Explicit proof state output via separate GUI panel (command
`isabelle.state`).
* HTML preview via separate GUI panel (command `isabelle.preview`).
* Rich completion information: Isabelle symbols (e.g. `\forall` or
`\<forall>`), outer syntax keywords, formal entities, file-system paths,
BibTeX entries etc.
* Spell-checking of informal texts, including dictionary operations: via the
regular completion dialog.
## Requirements
### Isabelle/VSCode Installation
* Download a recent Isabelle development snapshot from
<https://isabelle.sketis.net/devel/release_snapshot>
* Unpack and run the main Isabelle/jEdit application as usual, to ensure that
the logic image is built properly and Isabelle works as expected.
* Download and install VSCode from <https://code.visualstudio.com>
* Open the VSCode *Extensions* view and install the following:
+ *Isabelle* (needs to fit to the underlying Isabelle release).
+ *Prettify Symbols Mode* (important for display of Isabelle symbols).
+ *bibtexLanguage* (optional): it gives `.bib` a formal status, thus
`@{cite}` antiquotations become active for completion and hyperlinks.
* Restart the VSCode application to ensure that all extensions are properly
initialized and user settings are updated. Afterwards VSCode should know about
`.thy` files (Isabelle theories) and `.ML` files (Isabelle/ML modules).
The Isabelle extension is initialized when the first Isabelle file is opened.
It requires a few seconds to start up: a small popup window eventually says
*"Welcome to Isabelle ..."*.
### Further Preferences
* Preferred Color Theme: `Light+ (default light)`
* Alternative Color Theme: `Dark+ (default dark)` – with restrictions: some
color combinations don't work out properly.
* Recommended changes to default VSCode settings:
```
"editor.acceptSuggestionOnEnter": "off",
"editor.lineNumbers": "off",
"editor.renderIndentGuides": false,
"editor.rulers": [80, 100],
"editor.wordBasedSuggestions": true,
```
## Known Limitations of Isabelle/VSCode
* Lack of specific support for the Isabelle fonts: these need to be
manually installed on the system and configured for VSCode (see also
`$ISABELLE_FONTS` within the Isabelle environment).
**Note:** As the Isabelle fonts continue to evolve, installed versions need
to be updated according to each new Isabelle version.
* Isabelle symbols are merely an optical illusion: it would be better to make
them a first-class Unicode charset as in Isabelle/jEdit.
* Isabelle symbol abbreviations like "-->" are not accepted by VSCode.
* Lack of formal editor perspective in VSCode: only the cursor position is
used (with some surrounding lines of text).
* Lack of formal markup in prover messages and popups.
* Lack of pretty-printing (logical line breaks) according to window and font
dimensions.
* Lack of GUI panels for Sledgehammer, Query operations etc.
* Big theory files may cause problems to the VSCode rendering engine, since
messages and text decorations are applied to the text as a whole (cf. the
minimap view).