Fix Java detection fallback when Ballerina dependencies directory is missing

[Copilot]

Purpose

When the dependencies folder is absent from the Ballerina home directory, Java detection fails immediately with an error rather than falling back to JAVA_HOME or platform-specific locations.

Goals

Implement a prioritized 3-step JDK lookup:

1. ballerinaHome/dependencies — check inside the active distribution first
2. baseHome/dependencies — check one level up (sibling to distributions/)
3. JAVA_HOME / platform-specific system JDK — final fallback

Approach

Refactored findHighestVersionJdk() in server.ts into three composable functions:

• findJdkInDirectory(directory) — pure directory scan, no fallback; returns null if dir missing or no matching JDK pattern
• findSystemJdk() — checks JAVA_HOME (with WSL support) and well-known platform paths (/usr/lib/jvm, ProgramFiles\Java, etc.)
• findHighestVersionJdk(directory) — backward-compatible wrapper: findJdkInDirectory(dir) ?? findSystemJdk()

Both getServerOptionsUsingJava (language server startup) and getJavaCommand (debugger) now use the explicit 3-step chain:

const jdkDir = findJdkInDirectory(join(ballerinaHome, 'dependencies'))
    ?? findJdkInDirectory(join(baseHome, 'dependencies'))
    ?? findSystemJdk();

Previously, findHighestVersionJdk returned null immediately when the directory didn't exist — bypassing the JAVA_HOME fallback entirely — and both callers threw an error without retrying alternative paths.

UI Component Development

• Added reusable UI components to the ui-toolkit. Follow the intructions when adding the componenent.
• Use ui-toolkit components wherever possible. Run npm run storybook from the root directory to view current components.
• Matches with the native VSCode look and feel.

Manage Icons

• Added Icons to the font-wso2-vscode. Follow the instructions.

User stories

Ballerina extension can now start the language server and debugger even when the bundled JDK (dependencies/) is absent, using JAVA_HOME as a fallback — previously a hard failure.

Release note

Fixed Java detection in the Ballerina extension: the extension now correctly falls back to JAVA_HOME when the Ballerina dependencies directory does not exist.

Documentation

N/A — internal runtime behavior change, no user-facing configuration change.

Training

N/A

Certification

N/A

Marketing

N/A

Automation tests

• Unit tests

  No existing unit test infrastructure for this module; logic validated via scenario simulation covering: normal install, missing dependencies dir (JAVA_HOME fallback), JDK inside ballerinaHome, no JDK found (error).

• Integration tests

  N/A

Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines? yes
• Ran FindSecurityBugs plugin and verified report? no
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets? yes

Samples

N/A

Related PRs

N/A

Migrations (if applicable)

N/A

Test environment

Validated logic against the following scenarios on Linux:

• Typical .ballerina/distributions/ballerina-x.y.z install with dependencies/ present
• Missing dependencies/ folder with JAVA_HOME set
• JDK located inside ballerinaHome/dependencies
• No JDK found in any location

Learning

N/A

Original prompt

ballerina extension check java in ballerina home. If balleinahome/dependency folder not exist java pickup failed.

What should we need to check ballrina home /dependencis folder first

If java cannot find there then check goback one folder from java home and check dependencies folder and if java has it

If not use environment JAVA_HOME to pick jre

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