fix(quality): keep Django and unittest hooks out of the dead-code list (#228)

changelog.d/228-django-unittest-hooks.md

@@ -0,0 +1,21 @@
+### Fixed — Django and unittest hooks no longer read as dead code
+
+Before: `--quality-delta` reported a Python hook as dead when no call in the tree named it. unittest and Django call
+`setUp`, `tearDown`, `setUpClass` and `setUpTestData` themselves. The runner calls each `test*` method. A closure inside a
+method that called `self.hook()` also lost the call. Each such method appeared as dead code.
+
+Now: the tool treats these names as called. It covers `setUpModule`, `tearDownModule`, `load_tests`, `runTest`, `asyncSetUp` and `asyncTearDown` too. The pytest xunit hooks `setup_module`, `teardown_module`,
+`setup_function`, `teardown_function`, `setup_class`, `teardown_class`, `setup_method` and `teardown_method` count as called too. A `test*`
+method (any name that starts with `test`) and an xunit hook count as called only in a test module: a path `isTestPath` accepts, or a Django `tests.py`. A closure
+that calls `self.` or `cls.` keeps the overrides of the method it calls live. A closure that binds `self` or `cls` as its own
+parameter does not.
+
+The HEAD snapshot scheme moves from 22 to 23. Old cached snapshots are not used.
+
+Not covered, still reported: pytest's conftest hooks such as `pytest_configure`. (`@pytest.fixture` functions are not reported as dead code here.)
+
+The hook names live in one table per framework (`kUnittestHooks`, `kXunitHooks`, `kUnittestModuleHooks` in `quality.h`), shared with `--dead-code` and `--safe-delete`, which now also skip `setUpTestData` and `runTest` in a TestCase subclass.
+
+Limit: the name check ignores types and scope. A method named `setUp`, `tearDown` or `load_tests` in application code is also treated as called. In a test module, any def named `test*` counts as called, nested defs and helper functions included. The tool errs toward live here.
+
+A closure that binds `self` or `cls` as its own parameter does not count, even for `def cb(self=self)`.

changelog.d/versions.md

@@ -7,4 +7,4 @@ Python rebind-withholding records a 224 placeholder on theirs; 226 sits above ev
 (212 to 225). A cache written by 0.6.8 is re-parsed once. `kCacheVersion` 36 → 40: a Rust binding typed only through a trait
 (`&dyn T`, `impl T`, a bound), a Rust `impl T for X` block and a JS/TS binding written after its declaration are new binding
 records, so a cache written before them is rejected and rebuilt (the branches that added them used 37, 38 and 39). The
-quality-snapshot scheme stays 22. The session legend dictionary is `dictv=2259c5025ac90271 entries=930`.
+quality-snapshot scheme moves 22 → 23 (#228: Django and unittest hooks and closure self-dispatch change the dead set; old snapshots are not used). The session legend dictionary is `dictv=2259c5025ac90271 entries=930`.

src/langfacts.h

@@ -116,6 +116,14 @@ struct LangFacts
     /// open too (ifacedispatch.h). A Kotlin-only tree is unchanged.
     bool samFromJavaLambdas = false;
 
+    /// Python: unittest, Django and pytest call setUp, tearDown, setup_method and the other test-framework hooks themselves
+    /// (quality.h pythonFrameworkInvokedSymbol).
+    bool frameworkEntryHooks = false;
+
+    /// Python: a closure inside a method can call `self.hook()` / `cls.hook()` for its host, so a receiver-bound call dispatches
+    /// through the host's overrides (quality.h pythonReceiverParameters, pythonDispatchRequests). A separate fact from the hooks.
+    bool closureReceiverDispatch = false;
+
     /// Kotlin: an `interface` is a class_declaration like a class (queries/kotlin/tags.scm: "both land here as @definition.class"),
     /// so the symbol's kind cannot tell the two apart; shared code that needs an interface (ifacedispatch.h's lambda test) reads a
     /// class of such a language as a possible one.
@@ -182,7 +190,7 @@ inline constexpr std::array<std::string_view, 3> kJavaObjectMethods = { "equals"
 inline constexpr std::array<LangFacts, kLangCount> kLangFacts = { {
     { .lang = Lang::Cpp, .defectShapeNeedsMacroSet = true, .noNestedNamedFunctions = true, .memberSeparator = "::",
       .transitiveIncludes = true },
-    { .lang = Lang::Python, .baseImportEvidence = BaseImportEvidence::PythonImport },
+    { .lang = Lang::Python, .frameworkEntryHooks = true, .closureReceiverDispatch = true, .baseImportEvidence = BaseImportEvidence::PythonImport },
     { .lang = Lang::TypeScript, .overloadSignatures = true, .structuralTyping = true, .importBoundConstruction = true, .baseImportEvidence = BaseImportEvidence::JsImport,
       .writtenBindingUndecided = true },
     { .lang = Lang::Go, .structuralTyping = true },