Fix line navigation when opening files with line fragments

[MrToph]

This PR fixes two line-navigation regressions for file links that include a fragment like #L99.

Related issue: #170405

Rationale

File deep-linking is increasingly important with external AI coding tools that use VS Code as the editor/diff viewer. In these workflows, opening a file at an exact location (and, in related scenarios, specific ranges) is core to review and iteration speed. Preserving URI fragments such as #L99 or #L99-L105 avoids making users manually browse large files and lose the exact location being referenced.

Problem summary

VS Code supports opening file links with line fragments (e.g. #L99), but the fragment was getting dropped in two important paths:

1. Inside VS Code when clicking a relative file:// link.
2. Outside VS Code when opening via protocol URL (vscode://file/...#L99 or code-oss://file/...#L99).

Reproduction matrix (with concrete paths)

Target file for all cases:

• /tmp/vscode-link-repro/target.txt

Contents:

Line 1 ...
Line 2 ...
<continues 100 times>

Source file used for in-editor link clicks:

• /tmp/vscode-link-repro/source.txt

Contents:

relative: file://./target.txt#L99
absolute: file:///tmp/vscode-link-repro/target.txt#L99

Cases:

1. Inside VS Code × relative file://

• Link: file://./target.txt#L99 (from /tmp/vscode-link-repro/source.txt)
• Before: opens file, does not go to line 99
• After this PR: opens file and goes to line 99

2. Inside VS Code × absolute file://

• Link: file:///tmp/vscode-link-repro/target.txt#L99
• Before: goes to line 99
• After: unchanged (still works)

3. Outside VS Code (macOS open) × vscode:// URL

• Code - OSS command:
  • open -b com.visualstudio.code.oss -u "code-oss://file/tmp/vscode-link-repro/target.txt#L99"
• VS Code stable command:
  • open -b com.microsoft.VSCode -u "vscode://file/tmp/vscode-link-repro/target.txt#L99"
• Before: opens file, does not go to line 99
• After this PR: opens file and goes to line 99

4. Outside VS Code (macOS open) × file:// URL

• Command:
  • open -b com.visualstudio.code.oss -u "file:///tmp/vscode-link-repro/target.txt#L99"
• Behavior: opens file, does not go to line 99
• Status: not fixable in VS Code. macOS delivers this as open-file with a filesystem path and strips the URI fragment (#L99) before VS Code receives it.

What changed

1. Editor link handling (src/vs/editor/contrib/links/browser/links.ts)

• Preserve query/fragment when resolving relative file://./... links against the active model URI.
• This fixes in-editor relative links losing #L....

2. Protocol URL handling in main process (src/vs/code/electron-main/app.ts)

• Preserve query and fragment when converting protocol file URLs into fileUri openables.

3. Openable resolution (src/vs/platform/windows/electron-main/windowsMainService.ts)

• Extract line selection from URI fragment (e.g. #L99) before resolving local file path.
• Carry selection into editor open options, while still using filesystem path for file existence checks.

Tests

Added regression tests:

• src/vs/editor/contrib/links/test/browser/linkDetectorUtils.test.ts

Validated:

• Relative file://./...#L99 now preserves fragment and resolves to line selection.
• Existing absolute in-editor behavior remains unchanged.

[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

@bpasero

Matched files:

• src/vs/code/electron-main/app.ts
• src/vs/platform/windows/electron-main/windowsMainService.ts

@deepak1556

Matched files:

• src/vs/code/electron-main/app.ts

[MrToph]

@microsoft-github-policy-service agree

[MrToph]

this is a refactor of the old code from src/vs/editor/contrib/links/browser/links.ts, I kept it functionally equivalent except the final with query + fragment.

[MrToph]

had to specify this because of a type error when using options.selection below.