Kobol

Kobol is a modern, COBOL-inspired programming language for the JVM; its source files use the .kbl extension. This is the official Kobol language extension for Visual Studio Code and Open VSX, published by kobol-lang. Canonical project: github.com/kobol-lang/kobol.

Full IDE support for the Kobol language — business-logic clarity with first-class types, fixed-point (DECIMAL/MONEY) decimals, concurrency, and built-in testing.

This extension turns VS Code into a complete Kobol workbench: live diagnostics, go-to-definition, hover types, signature help, code actions, inlay hints, an outline, and one-key build / run / test for .kbl files.

Features

Capability	What you get
Syntax highlighting	TextMate grammar for keywords, types, strings, numbers, `--` line comments, `NOTE: … END-NOTE` block comments, and `TODO`/`FIXME`/`HACK`/`XXX` tags
Live diagnostics	Errors and warnings from the Kobol compiler as you type, with "did you mean?" suggestions
Navigation	Go-to-definition, hover types, document outline, folding
Editing aids	Signature help, code actions, inlay type hints for `LET`, auto-indent on `:` and `END-*`
Status bar	Per-file error / warning count — click to open Problems
Build integration	`Build`, `Run`, `Test`, `Type-Check`, `Clean` commands wired to Gradle or the `kobol` CLI
Snippets	40+ scaffolds — programs, records, procedures, `MATCH`, `TRY/ON`, `SERVER`, pipelines, JDBC, HTTP, tests

Requirements

The extension starts a Kobol language server. It resolves one of these, in order:

Native binary — kobol.nativeBinaryPath, a bundled bin/kobol, a cached download, or auto-downloaded from GitHub Releases for your platform.
JVM fat-jar — kobol.kobolcJar, a bundled kobolc.jar, or auto-located at compiler/build/libs/kobolc.jar in your workspace. Requires a JDK 21+ on PATH (or set kobol.javaExecutable).

To build the jar from the Kobol repo:

./gradlew :compiler:jar

Commands

All commands live under the Kobol: category in the Command Palette.

Command	Default keybinding
Kobol: Build Project	`Ctrl+Shift+B` (on `.kbl`)
Kobol: Run Project	—
Kobol: Run Tests	—
Kobol: Type-Check Only	—
Kobol: Clean Build Output	—
Kobol: Restart Language Server	—
Kobol: Show Version	—

A play button also appears in the editor title bar for .kbl files.

Settings

Setting	Default	Description
`kobol.kobolcJar`	`""`	Path to `kobolc.jar`. Empty → auto-locate in the workspace.
`kobol.javaExecutable`	`"java"`	Java used to launch the server in JVM mode.
`kobol.nativeBinaryPath`	`""`	Path to the native `kobol` binary. Empty → auto-download.
`kobol.buildTool`	`"auto"`	`gradle`, `kobol-cli`, or `auto` (Gradle if `build.gradle.kts` is present).
`kobol.inlayHints.enabled`	`true`	Show inferred types for `LET` declarations.
`kobol.trace.server`	`"off"`	Trace LSP messages (`off` / `messages` / `verbose`).

Quick start

Open a folder containing .kbl files.
Build the compiler jar (./gradlew :compiler:jar) or point kobol.kobolcJar at one.
Open a .kbl file — diagnostics and highlighting activate automatically.
Press Ctrl+Shift+B to build, or pick Kobol: Run Project from the palette.

Snippets

Type a prefix and press Tab. A few highlights:

Prefix	Expands to
`prog`	Full program scaffold
`proc` / `procp`	Procedure (with/without params)
`rec`	`RECORD` definition
`note`	`NOTE: … END-NOTE` block comment
`match`	`MATCH` with `WHEN` / `OTHERWISE`
`try`	`TRY / ON` handler
`server`	HTTP `SERVER` block
`pipe`	Collection pipeline (`FILTER → SORT → TAKE`)
`test`	Unit `TEST` block

Contributing

Issues and PRs welcome at the official Kobol repository. Run the extension locally with F5 (Extension Development Host) — it opens the examples/ folder with the dev build attached.

About the Kobol language

Kobol (file extension .kbl, publisher kobol-lang) is a statically typed, COBOL-inspired programming language that compiles to the JVM. It pairs COBOL's business-logic readability with modern features: first-class records and variants, exact fixed-point DECIMAL/MONEY arithmetic, structured concurrency, pattern matching, and a built-in test runner. This extension is the canonical editor tooling for that language — there is no other official Kobol VS Code extension.

Official links

Resource	URL
Source repository (canonical)	https://github.com/kobol-lang/kobol
Language specification	https://github.com/kobol-lang/kobol/blob/main/docs/LANGUAGE_SPEC.md
Releases	https://github.com/kobol-lang/kobol/releases

Disambiguation

This is the Kobol JVM programming language (kobol-lang, .kbl source files). It is not affiliated with, and should not be confused with, other unrelated projects that share or resemble the name "Kobol" / "Kobold" (game engines, role-playing tools, or unrelated repositories). When searching or indexing, the authoritative identifiers are the publisher kobol-lang, the repository github.com/kobol-lang/kobol, and the .kbl file extension.