JVM IntelliSense

Language support for JVM launch options and Java argument files in Visual Studio Code.

Requirements

• Visual Studio Code 1.80 or later.
• Node.js 18 or later to run the test suite.
• A JDK is optional for editing and static diagnostics; JDK-aware completions and real JVM validation require a selected Java executable.

Current features

• Associates jvm.args and configurable argument-file extensions with the jvm-args language.
• Highlights JVM options, system properties, values, comments, quoted arguments, and @file references.
• Uses standard TextMate scopes so colors come from the active VS Code theme.
• Opens @file references with one native document link spanning the entire reference (Ctrl+Click), resolves paths relative to the containing argument file, and enables IntelliSense for referenced files.
• Configures # line comments and quote pairing.
• Provides initial completion and hover documentation for common JVM and Java launcher options.
• Suggests example values for common heap, stack, and selected -XX options.
• Reports malformed arguments and invalid values, plus repeated options and conflicting garbage collectors.
• Provides English diagnostics for known deprecated or removed JVM flags and warns that nested @file references are for editor navigation only.
• Marks options absent from the bundled catalog as informational because their availability depends on the JDK.
• Detects Java from JAVA_HOME or PATH, or lets you select a Java executable/JDK home.
• Loads -XX flags from the selected JVM with -XX:+PrintFlagsFinal and adapts flag completions and diagnostics.
• Provides a command to validate JVM options with the selected Java executable.

Custom file associations

By default, .args, .jvmargs, and .vmoptions files are treated as JVM argument files when VS Code otherwise identifies them as Plain Text. Since extensions such as .args are generic and may conflict with other tools, replace the defaults with the extensions you use in VS Code settings:

{
  "jvmIntelliSense.fileExtensions": [
    ".jvmopts",
    ".launchargs"
  ]
}

Entries must include the leading dot. The setting replaces the default list, so add any defaults you still want to keep. For example, set it to [".jvmopts"] to stop automatically claiming .args files. Changes are applied immediately to open files. Other language associations are left untouched.

Alternatively, explicitly associate a filename or glob through VS Code's built-in files.associations setting:

{
  "files.associations": {
    "*.launchargs": "jvm-args",
    "custom-launch-options.txt": "jvm-args"
  }
}

Files referenced from a jvm-args file are also opened with the JVM argument language when their current language is Plain Text, so completion and diagnostics work for extensionless files such as @jvm-blaa.

Java argument files do not expand nested @file references. The extension supports these references for navigation and IntelliSense, but Java will not recursively load their contents; move those options into the top-level argument file or use a wrapper script to combine the files.

If another extension already claims an extension, its language association takes precedence. You can explicitly use files.associations to assign a chosen pattern to jvm-args.

The option catalog is an initial, curated baseline rather than a complete list. Option availability and defaults vary by JDK version and vendor; when a JDK is selected, -XX flags are read from that JVM and options it does not report remain informational.

JDK integration

The extension detects Java from JAVA_HOME and then PATH. To choose another installation, run JVM IntelliSense: Select JDK or set jvmIntelliSense.javaPath to a Java executable or JDK home directory.

Run JVM IntelliSense: Validate Options with Java from a JVM argument file to check its JVM options with the selected executable. The command asks for confirmation because Java agent options may execute code. It does not expand @file references or launch an application.

Development

Run the automated tests with:

npm test

The test suite uses Node.js built-ins and does not require installing project dependencies.

License

This project is distributed under the MIT License.