Theia Modula-2/Pascal/Oberon: Short Tutorial

This is a Modula-2, Pascal and Oberon IDE built on Eclipse Theia (modula2-ide/). All three languages get the same depth: syntax highlighting, snippets, auto-uppercasing, outline / hover / go-to-definition / references / rename, formatting, Build-Run tasks, GDB debug, and project wizards.

Language	Files	Validators	Compiler	Debug type	Project file
Modula-2	`.mod`/`.def`	Coco/R `gm2` grammar	`gm2`	`modula2`	`modula2.json`
Pascal	`.pas`/`.pp`/`.p`	8 Coco/R dialects	`fpc`, Blaise	`pascal`	`pascal.json`
Oberon	`.Mod`/`.mod`/`.om` (`.def`/`.od`)	O07, Oberon-2, Ulm	`voc`, `ulmo`	`oberon`	`oberon.json`

1. Prerequisites

node --version  # >=24
yarn --version  # 1.x Classic
gm2 --version
fpc -iV
voc         # prints its banner; ulmo likewise
gdb --version

Debian/Ubuntu: sudo apt install gm2 gdb binutils fp-compiler. voc/ulmo come from their own distributions. Editing features (hover, outline, rename, formatting) work without any compiler.

2. Build and run

cd modula2-ide
yarn
yarn build
yarn start:browser   # http://localhost:3000
# or
yarn start:electron

Standalone editor plugins (VS Code-compatible) ship as versioned zips: modula2-language-*.zip, pascal-language-*.zip, oberon-language-*.zip.

3. Open an example

Example	Project file	Main file
`examples/hello/`	`modula2.json`	`src/Main.mod`
`examples/hello-pascal/`	`pascal.json`	`src/Main.pas`
`examples/hello-oberon/`	`oberon.json`	`src/Main.Mod`

pascal.json:

{
  "name": "Hello",
  "compiler": {"type": "fpc", "path": "fpc", "options": []},
  "sourceDirectories": ["src"],
  "main": "src/Main.pas"
}

oberon.json has the same shape with "type": "voc" (or "ulm") and "main": "src/Main.Mod".

4. Edit

Keywords auto-uppercase (begin -> BEGIN, but beginning is left alone). Oberon matching stays case-sensitive; Pascal is case-insensitive.
Try: hover, F12 go-to-definition, Shift+F12 references, F2 rename, Ctrl+Shift+O outline, Shift+Alt+F format.
Cross-file jumps work through USES (Pascal), IMPORT (Oberon, alias-aware) and IMPORT/FROM (Modula-2 .def files).
Snippets: Modula-2 mod/proc/if/defmod, Pascal program/unit/proc/func, Oberon module/proc/func.

Commands (via F1 / Ctrl+Shift+P):

Pascal: New Pascal Project / New Unit, Oberon: New Oberon Project / New Module, Modula-2: New Modula-2 Project / New Module / New Definition Module
Pascal / Oberon / Modula-2: Validate Project, About, theme commands

Each language has its own Project explorer view (right-click for New Unit/Module Here, Build, Refresh).

5. Build and run

With the project folder open in the workspace:

F1 > Pascal: Build — builds bin/<name> (fpc -M<dialect>, dialect from modula2.pascal.dialect, default Free Pascal)
Oberon: Build — runs voc (or ulmo) frontend check on the main module
Modula-2: Build — gm2 -fiso -g
Each also offers Build File / Clean / Rebuild / Run, or use the terminal: fpc -o bin/Hello src/Main.pas, voc src/Main.Mod, gm2 -o bin/Hello src/Main.mod

Build errors appear in Problems panel, click to jump to source.

6. Debug

Build first (passes debug info: -g/-gl).
Set breakpoint in gutter.
Run > Start Debugging, type pascal, oberon or modula2. program defaults to bin/<name>.

The example launch.json files set "preLaunchTask": "<Lang>: Build", so debugging always builds first. You get: continue/step over/into/out, call stack, Locals + Module scopes, hover/evaluate.

7. Troubleshooting

Language features missing: check plugins/<lang>-language/ was synced by yarn build:language.
No validator diagnostics: set modula2.pascal.validators / modula2.oberon.validators to the pilot binaries built by each grammars/*/build.sh. Unconfigured dialects stay silent by design.
fpc/voc not found: set "compiler": {"path": ...} in pascal.json / oberon.json (or the *.compiler.path preference).
Debug program not found: run <Lang>: Build first.

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