Theia Modula-2: Short Tutorial

Modula-2 Studio is a GNU Modula-2 IDE built on the Eclipse Theia IDE product template (modula2-ide/), with the full theia-ide extension set (search, tasks, terminal, SCM, debug, …).

It gives you: .mod/.def highlighting, snippets, auto-uppercasing, outline / hover / go-to-definition / references / rename, formatting, gm2 Build-Run, GDB debug, and modula2.json projects.

Pascal and Oberon support is parked in attic/ for now and will be re-enabled once Modula-2 works correctly.

1. Prerequisites

node --version  # >=24
yarn --version  # 1.x Classic
gm2 --version
gdb --version

Debian/Ubuntu: sudo apt install gm2 gdb binutils. 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

The standalone editor plugin (VS Code-compatible) ships as a versioned zip: modula2-language-*.zip.

3. Open an example

Open folder examples/hello/
Look at:
- src/Main.mod — sample program
- modula2.json — project descriptor:

{
  "name": "Hello",
  "compiler": {"type": "gnu-modula-2", "path": "gm2", "options": []},
  "sourceDirectories": ["src"],
  "main": "src/Main.mod"
}

4. Edit Modula-2

Create Foo.mod / Foo.def. Keywords auto-uppercase (begin -> BEGIN, but beginning is left alone).
Try: hover, F12 go-to-definition (incl. .def cross-file), Shift+F12 references, F2 rename, Ctrl+Shift+O outline, Shift+Alt+F format.
Snippets: mod, proc, if, defmod.

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

Modula-2: New Modula-2 Project / New Module / New Definition Module
Modula-2: Validate Project
Modula-2: About Modula-2 IDE

5. Build and run

With modula2.json open in workspace:

F1 > Modula-2: Build — builds bin/<name>
Modula-2: Build File / Clean / Rebuild / Run
Or terminal: gm2 -o bin/Hello src/Main.mod && ./bin/Hello

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

6. Debug

Build with Modula-2: Build (passes -g by default, so breakpoints bind).
Set breakpoint in gutter.
Run > Start Debugging, type modula2. program defaults to bin/<name>.

The example launch.json sets "preLaunchTask": "Modula-2: Build", so debugging always builds first. You get: continue/step over/into/out, call stack, Locals + Module scopes, hover/evaluate.

Right-click any file in the Modula-2 Project view for New Module Here, Build and Refresh without leaving the explorer.

7. Troubleshooting

Language features missing: check plugins/modula2-language/ was synced by yarn build:language.
gm2 not found: set "compiler": {"path": "/usr/bin/gm2"} in modula2.json.
Debug program not found: run Modula-2: Build first.

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