feat(completion): trigger import completion on space

[16bit-ykiko]

Summary

• Register space as a completion trigger character so that typing import immediately opens the module name suggestion list (same UX as #include < triggering header suggestions).
• Gate space triggers on both sides:
  • Server: space-triggered requests outside an import context are answered with an empty list instead of falling through to a full completion build, so clients without request-side filtering (nvim, zed) are not charged a heavyweight completion for every space keystroke.
  • VS Code extension: middleware short-circuits space triggers unless the line prefix is import or export import , avoiding the request round-trip entirely in the common case.
• Add FIXME/TODO annotations for known limitations (textual import detection, self-import not excluded, module map refreshed on save only).

Approach

Follows the same pattern as TypeScript/Haxe language extensions (vscode#67714): the server advertises space as a trigger character and the client does a cheap string check to avoid flooding the server — with the addition that the server independently enforces the same rule, so the UX guarantee does not depend on any particular editor integration.

Test plan

• Unit tests: detect_completion_context (dotted module prefix, partition prefix, empty partition, leading whitespace, export import, multiline import, mid-line cursor truncation) and complete_module_import (dotted/partition prefix filtering, prefix-equals-full-name).
• Integration tests: server capability advertises " " in triggerCharacters; space trigger on an import line serves module completions; space trigger elsewhere returns an empty list.
• VS Code e2e: space-triggered completion outside an import line yields no server items (middleware gate).
• Full suites green locally: unit 1008 passed, integration 285 passed, smoke 3/3, vscode e2e 7 passing in all three scenarios (RelWithDebInfo).

Summary by CodeRabbit

• New Features
  • Improved module import completion with support for dotted and partition-style prefixes.
  • Added space-triggered completion for import and export import contexts.
  • Extended completion trigger characters to include space and *.
• Bug Fixes
  • Prevented module/include completion candidates from appearing on space-triggered requests in non-import contexts.
• Tests
  • Expanded unit, integration, and VS Code e2e coverage for space-trigger gating and additional import patterns.

[coderabbitai]

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ℹ️ Recent review info

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Run ID: da668d0a-3087-4e38-8568-8b3d51661d65

📥 Commits

Reviewing files that changed from the base of the PR and between 59dc9c1 and f8dd539.

📒 Files selected for processing (2)

• src/server/service/feature_router.cpp
• tests/integration/features/test_completion.py

🚧 Files skipped from review as they are similar to previous changes (2)

• tests/integration/features/test_completion.py
• src/server/service/feature_router.cpp

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📝 Walkthrough

Walkthrough

Adds space as an LSP completion trigger, propagates trigger context through the server, filters VS Code space-triggered requests by import context, and expands unit, integration, and end-to-end completion coverage.

Changes

Space-triggered completion

Layer / File(s)	Summary
Completion trigger routing src/server/service/feature_router.*, src/server/transport/lsp_client.cpp	The server advertises space as a completion trigger, forwards optional trigger characters, and returns no results for space-triggered requests outside import contexts.
VS Code completion filtering editors/vscode/src/extension.ts, editors/vscode/src/test/e2e.test.ts	Middleware permits space-triggered completion only after import or export import , with an end-to-end test covering non-import code.
Completion request and context coverage tests/tools/client.py, tests/integration/features/*, tests/unit/syntax/completion_tests.cpp, tests/integration/features/test_server.py, src/syntax/completion.cpp	Test clients send trigger-character contexts; tests cover import, include, non-import, module-prefix, and advertised-trigger behavior, alongside completion context TODO/FIXME notes.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant VSCode
  participant LSPClient
  participant FeatureRouter
  participant CompletionContext

  VSCode->>LSPClient: completion request with trigger character
  LSPClient->>FeatureRouter: completion(position, trigger_character)
  FeatureRouter->>CompletionContext: detect preamble context
  FeatureRouter-->>LSPClient: filtered or normal completion result
  LSPClient-->>VSCode: completion response

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Possibly related PRs

• clice-io/clice#394 — Both use the import/include completion-context machinery.
• clice-io/clice#488 — Both modify the FeatureRouter::completion path.
• clice-io/clice#511 — Both modify FeatureRouter::completion request plumbing.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: enabling import completion when space triggers completion.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/import-completion-trigger

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[chatgpt-codex-connector]

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