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[linter-miner] Add unchecked-deferred-close linter #67481
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,15 @@ | ||
| package basic | ||
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| import ( | ||
| "os" | ||
| ) | ||
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| func bad(filename string) error { | ||
| f, err := os.Open(filename) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| defer f.Close() // want "defer close\\(\\) call ignores error return value" | ||
| // ... use f | ||
| return nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,30 @@ | ||
| package basic | ||
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| import ( | ||
| "fmt" | ||
| "os" | ||
| ) | ||
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| func good(filename string) error { | ||
| f, err := os.Open(filename) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| defer func() { | ||
| if err := f.Close(); err != nil { | ||
| fmt.Fprintf(os.Stderr, "close error: %v\n", err) | ||
| } | ||
| }() | ||
| // ... use f | ||
| return nil | ||
| } | ||
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| // NoReturnClose is a mock type that has Close() with no error return | ||
| type NoReturnClose struct{} | ||
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| func (n *NoReturnClose) Close() {} | ||
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| func goodNoError() { | ||
| n := &NoReturnClose{} | ||
| defer n.Close() // OK: Close() returns nothing | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,132 @@ | ||
| // Package unchecked deferredclose implements a Go analysis linter that flags | ||
| // defer close() calls without error checking, which can hide resource cleanup failures. | ||
| package unchecked_deferredclose | ||
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| import ( | ||
| "go/ast" | ||
| "go/types" | ||
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| "golang.org/x/tools/go/analysis" | ||
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| "github.com/github/gh-aw/pkg/linters/internal/analyzerutil" | ||
| "github.com/github/gh-aw/pkg/linters/internal/filecheck" | ||
| "github.com/github/gh-aw/pkg/linters/internal/nolint" | ||
| ) | ||
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| // Analyzer is the unchecked-deferred-close analysis pass. | ||
| var Analyzer = analyzerutil.New("unchecked_deferredclose", "reports defer close() calls without error checking that may hide resource cleanup failures", run) | ||
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| var builtinErrorType = types.Universe.Lookup("error").Type() | ||
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| func run(pass *analysis.Pass) (any, error) { | ||
| noLintIndex, generatedFiles, err := analyzerutil.Indexes(pass) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
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| nodeFilter := []ast.Node{(*ast.DeferStmt)(nil)} | ||
| return analyzerutil.Preorder(pass, nodeFilter, func(n ast.Node) { | ||
| analyzeDeferClose(pass, n, generatedFiles, noLintIndex) | ||
| }) | ||
| } | ||
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| // analyzeDeferClose checks for defer close() calls that don't handle errors. | ||
| func analyzeDeferClose(pass *analysis.Pass, n ast.Node, generatedFiles filecheck.GeneratedIndex, noLintIndex nolint.DirectiveIndex) { | ||
| deferStmt, ok := n.(*ast.DeferStmt) | ||
| if !ok { | ||
| return | ||
| } | ||
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| // The defer statement's Call is already a *CallExpr | ||
| callExpr := deferStmt.Call | ||
| if callExpr == nil { | ||
| return | ||
| } | ||
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| // Check if the call is to a Close() method | ||
| selector, ok := callExpr.Fun.(*ast.SelectorExpr) | ||
| if !ok || selector.Sel.Name != "Close" { | ||
| return | ||
| } | ||
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| // Ensure it has no arguments | ||
| if len(callExpr.Args) != 0 { | ||
| return | ||
| } | ||
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| position := pass.Fset.PositionFor(deferStmt.Pos(), false) | ||
| if filecheck.ShouldSkipFilename(position.Filename, generatedFiles) { | ||
| return | ||
| } | ||
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| if nolint.HasDirectiveForLinter(position, noLintIndex, "unchecked_deferredclose") { | ||
| return | ||
| } | ||
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| // Get the type of the receiver to check if Close() returns an error | ||
| if pass.TypesInfo == nil { | ||
| return | ||
| } | ||
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| // Get type of the object being closed (the receiver) | ||
| receiverType := pass.TypesInfo.TypeOf(selector.X) | ||
| if receiverType == nil { | ||
| return | ||
| } | ||
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| // Look for a Close method on this type | ||
| closeMethod, found := lookupClose(receiverType) | ||
| if !found { | ||
| return | ||
| } | ||
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| // Check if Close() returns an error | ||
| if sig, ok := closeMethod.Type().(*types.Signature); ok { | ||
| if sig.Results() == nil || sig.Results().Len() == 0 { | ||
| return | ||
| } | ||
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| // Check if the return type is error | ||
| lastResult := sig.Results().At(sig.Results().Len() - 1) | ||
| if lastResult.Type() != builtinErrorType { | ||
| return | ||
| } | ||
|
Contributor
There was a problem hiding this comment. The analyzer now checks the resolved method selection signature, with fixtures for |
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| // Report: defer close() ignores error return | ||
| pass.Reportf( | ||
| deferStmt.Pos(), | ||
| "defer close() call ignores error return value; consider handling errors explicitly", | ||
| ) | ||
| } | ||
| } | ||
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| // lookupClose searches for a Close method on the given type. | ||
| func lookupClose(typ types.Type) (types.Object, bool) { | ||
| // Unwrap pointer type if necessary | ||
| ptr, ok := typ.(*types.Pointer) | ||
| if ok { | ||
| typ = ptr.Elem() | ||
| } | ||
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| // If it's a named type, get its underlying type | ||
| if named, ok := typ.(*types.Named); ok { | ||
| for i := 0; i < named.NumMethods(); i++ { | ||
|
Check failure on line 113 in pkg/linters/unchecked-deferred-close/unchecked_deferredclose.go
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| method := named.Method(i) | ||
| if method.Name() == "Close" { | ||
| return method, true | ||
| } | ||
| } | ||
| } | ||
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| // Check interface types | ||
| if iface, ok := typ.(*types.Interface); ok { | ||
| for i := 0; i < iface.NumMethods(); i++ { | ||
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Check failure on line 123 in pkg/linters/unchecked-deferred-close/unchecked_deferredclose.go
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| method := iface.Method(i) | ||
| if method.Name() == "Close" { | ||
| return method, true | ||
| } | ||
| } | ||
| } | ||
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| return nil, false | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,17 @@ | ||
| //go:build !integration | ||
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| // Package unchecked_deferredclose_test provides tests for the unchecked_deferredclose analyzer. | ||
| package unchecked_deferredclose_test | ||
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| import ( | ||
| "testing" | ||
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| "golang.org/x/tools/go/analysis/analysistest" | ||
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| unchecked_deferredclose "github.com/github/gh-aw/pkg/linters/unchecked-deferred-close" | ||
| ) | ||
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| func TestUncheckedDeferredClose(t *testing.T) { | ||
| t.Parallel() | ||
| analysistest.Run(t, analysistest.TestData(), unchecked_deferredclose.Analyzer, "basic") | ||
| } |
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Updated the analyzer inventory in
doc.go, both README lists,documentedAnalyzers(), and the doc-sync enforcement tracking. It is documented as not yet enforced pending remediation of existing findings. Committed in 31de3ea.