HOTFIX: graceful fallback when tree-sitter-typescript not installed#281
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DevanshuNEU merged 2 commits intoMar 6, 2026
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…duction fix) The backend crashes on startup if tree-sitter-typescript is not installed because dependency_analyzer.py is imported at app init via dependencies.py. Fix: try/except around the import, fall back to JS parser (old behavior) if the TS parser package isn't available. App starts regardless. When tree-sitter-typescript IS installed, uses the proper TS/TSX parsers. When it's NOT installed, logs a warning and uses JS parser as fallback. This prevents Railway deploy failures from taking down the entire API.
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📝 WalkthroughWalkthroughThe change adds a guarded import for the TypeScript parser and a runtime flag ( Changes
Sequence Diagram(s)sequenceDiagram
participant Client
participant DependencyAnalyzer as DA
participant JSParser as JS (tree-sitter-javascript)
participant TSParser as TS (tree-sitter-typescript)
rect rgba(200,200,255,0.5)
Client->>DA: analyze_file_dependencies(file.ts)
DA->>DA: check _HAS_TS_PARSER / has_ts_parser
alt has_ts_parser == true
DA->>TSParser: use TS parser to parse file.ts
TSParser-->>DA: AST (imports)
else has_ts_parser == false
DA->>JSParser: fallback to JS parser to parse file.ts
JSParser-->>DA: AST (imports)
end
DA-->>Client: return dependency list
end
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~20 minutes Possibly related PRs
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Actionable comments posted: 1
🧹 Nitpick comments (2)
backend/services/dependency_analyzer.py (2)
31-42: Surface fallback mode to callers, not just startup logs.When
_HAS_TS_PARSERis false,.tsand.tsxfiles are still reported astypescript/tsxeven though they were parsed with the JS grammar. Sincebackend/dependencies.py:21-27instantiates this singleton eagerly, downstream consumers have no structured way to detect that those dependency graphs are best-effort. Exposing ahas_ts_parser/parser_modeflag on the analyzer and in analysis results would make this degradation explicit.🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed. In `@backend/services/dependency_analyzer.py` around lines 31 - 42, The analyzer currently hides that TypeScript files may be parsed with the JS grammar (controlled by _HAS_TS_PARSER) — add a clear attribute on the DependencyAnalyzer (e.g., self.has_ts_parser or self.parser_mode = 'ts'|'js-fallback') set where self.parsers is initialized and logged, and propagate that flag into all analysis results/return objects so downstream consumers (including the eagerly-instantiated singleton in backend/dependencies.py) can detect best-effort TS parsing; update the DependencyAnalyzer constructor to set the flag based on _HAS_TS_PARSER and ensure analysis methods include it in their returned result dict/objects.
26-34: Add a regression test for the missing-parser path.This hotfix changes startup behavior, but the referenced tests do not appear to exercise it:
backend/tests/test_dependency_analyzer.py:84-105only checks parser presence/object identity, andbackend/tests/test_dependency_analyzer.py:142-166cover the “TS parser installed” path. Please add a test that forces thetree_sitter_typescriptimport to fail, asserts initialization does not raise, and verifies the warning/fallback behavior.If helpful, I can draft the monkeypatch-based test case.
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed. In `@backend/services/dependency_analyzer.py` around lines 26 - 34, Add a regression test that simulates the missing tree-sitter-typescript import and verifies fallback behavior: use monkeypatch to make the tree_sitter_typescript import fail (or set backend.services.dependency_analyzer._HAS_TS_PARSER = False) before importing or reloading backend.services.dependency_analyzer, then assert import/initialization does not raise, assert logger.warning was called with a message about falling back, and assert that ts_lang and tsx_lang reference the same object as js_lang (i.e. ts_lang == js_lang and tsx_lang == js_lang). Reference symbols: _HAS_TS_PARSER, js_lang, ts_lang, tsx_lang, and logger.warning in backend.services.dependency_analyzer.
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.
Inline comments:
In `@backend/services/dependency_analyzer.py`:
- Around line 12-16: The import block that sets _HAS_TS_PARSER should only
swallow ModuleNotFoundError for the specific package name to avoid hiding
runtime import errors: change the except ImportError to except
ModuleNotFoundError and ensure it only applies to the attempted import of
tree_sitter_typescript (symbol: tree_sitter_typescript) so real initialization
errors still surface; update the initialization logic that sets _HAS_TS_PARSER
accordingly. Also add a unit test covering the fallback path used when
_HAS_TS_PARSER is False (the JS fallback path referenced in the file) and update
or add a test case for test_ts_parser_is_not_js to assert behavior when the
TypeScript parser package is missing. Ensure tests explicitly simulate
ModuleNotFoundError for tree_sitter_typescript rather than generic ImportError.
---
Nitpick comments:
In `@backend/services/dependency_analyzer.py`:
- Around line 31-42: The analyzer currently hides that TypeScript files may be
parsed with the JS grammar (controlled by _HAS_TS_PARSER) — add a clear
attribute on the DependencyAnalyzer (e.g., self.has_ts_parser or
self.parser_mode = 'ts'|'js-fallback') set where self.parsers is initialized and
logged, and propagate that flag into all analysis results/return objects so
downstream consumers (including the eagerly-instantiated singleton in
backend/dependencies.py) can detect best-effort TS parsing; update the
DependencyAnalyzer constructor to set the flag based on _HAS_TS_PARSER and
ensure analysis methods include it in their returned result dict/objects.
- Around line 26-34: Add a regression test that simulates the missing
tree-sitter-typescript import and verifies fallback behavior: use monkeypatch to
make the tree_sitter_typescript import fail (or set
backend.services.dependency_analyzer._HAS_TS_PARSER = False) before importing or
reloading backend.services.dependency_analyzer, then assert
import/initialization does not raise, assert logger.warning was called with a
message about falling back, and assert that ts_lang and tsx_lang reference the
same object as js_lang (i.e. ts_lang == js_lang and tsx_lang == js_lang).
Reference symbols: _HAS_TS_PARSER, js_lang, ts_lang, tsx_lang, and
logger.warning in backend.services.dependency_analyzer.
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backend/services/dependency_analyzer.py
- except ImportError -> except ModuleNotFoundError (won't swallow real init errors from an installed-but-broken package) - Added self.has_ts_parser attribute for downstream consumers - Added test_fallback_when_ts_parser_missing: monkeypatches _HAS_TS_PARSER=False, verifies init succeeds, flag is False, and JS fallback still parses TS imports correctly
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Actionable comments posted: 2
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.
Inline comments:
In `@backend/tests/test_dependency_analyzer.py`:
- Around line 106-107: The test hard-codes the expectation that
analyzer.has_ts_parser is True which fails when tree_sitter_typescript is
absent; update the test_has_ts_parser_flag assertion to compare
analyzer.has_ts_parser against the runtime-determined flag (e.g., use the actual
module/utility or fixture value that indicates TypeScript parser availability)
instead of asserting True so the test reflects the environment's parser
availability.
- Around line 106-121: Add missing type hints to the two test functions:
annotate test_has_ts_parser_flag(self, analyzer) as taking the appropriate
fixture types and returning None, and annotate
test_fallback_when_ts_parser_missing(self, monkeypatch, tmp_path) with
monkeypatch: pytest.MonkeyPatch, tmp_path: pathlib.Path (or Path) and -> None;
update the signature names in the file for test_has_ts_parser_flag and
test_fallback_when_ts_parser_missing to include these parameter types and a ->
None return, and add any needed imports (pytest.MonkeyPatch and Path) at the top
of the test file so the type annotations resolve, leaving all logic
(DependencyAnalyzer, _HAS_TS_PARSER monkeypatching, analyze_file_dependencies)
unchanged.
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backend/services/dependency_analyzer.pybackend/tests/test_dependency_analyzer.py
🚧 Files skipped from review as they are similar to previous changes (1)
- backend/services/dependency_analyzer.py
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PRODUCTION DOWN
Backend crashes on startup because
import tree_sitter_typescriptfails if the package isn't installed. Sincedependency_analyzer.pyis imported at app init viadependencies.py, this takes down the entire API.Fix
Falls back to JS parser (old behavior) if TS parser unavailable. App starts regardless. Logs a warning so we know when fallback is active.
Impact
1 file, +19 -6 lines. All 28 dependency analyzer tests pass.
Summary by CodeRabbit
Bug Fixes
Tests
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