feat: detect in nested blocks

pkg/analyzer/analyzer.go

@@ -36,64 +36,39 @@ func run(pass *analysis.Pass) (interface{}, error) {
 			return
 		}
 
-		for _, stmt := range body.List {
+		assignStmt := findNestedContext(pass, body, body.List)
-			assignStmt, ok := stmt.(*ast.AssignStmt)
+		if assignStmt == nil {
-			if !ok {
+			return
-				continue
-			}
-
-			t := pass.TypesInfo.TypeOf(assignStmt.Lhs[0])
-			if t == nil {
-				continue
-			}
-
-			if t.String() != "context.Context" {
-				continue
-			}
-
-			if assignStmt.Tok == token.DEFINE {
-				break
-			}
-
-			// allow assignment to non-pointer children of values defined within the loop
-			if lhs := getRootIdent(pass, assignStmt.Lhs[0]); lhs != nil {
-				if obj := pass.TypesInfo.ObjectOf(lhs); obj != nil {
-					if obj.Pos() >= body.Pos() && obj.Pos() < body.End() {
-						continue // definition is within the loop
-					}
-				}
-			}
-
-			suggestedStmt := ast.AssignStmt{
-				Lhs:    assignStmt.Lhs,
-				TokPos: assignStmt.TokPos,
-				Tok:    token.DEFINE,
-				Rhs:    assignStmt.Rhs,
-			}
-			suggested, err := render(pass.Fset, &suggestedStmt)
-
-			var fixes []analysis.SuggestedFix
-			if err == nil {
-				fixes = append(fixes, analysis.SuggestedFix{
-					Message: "replace `=` with `:=`",
-					TextEdits: []analysis.TextEdit{
-						{
-							Pos:     assignStmt.Pos(),
-							End:     assignStmt.End(),
-							NewText: []byte(suggested),
-						},
-					},
-				})
-			}
-
-			pass.Report(analysis.Diagnostic{
-				Pos:            assignStmt.Pos(),
-				Message:        "nested context in loop",
-				SuggestedFixes: fixes,
-			})
-
-			break
 		}
+
+		suggestedStmt := ast.AssignStmt{
+			Lhs:    assignStmt.Lhs,
+			TokPos: assignStmt.TokPos,
+			Tok:    token.DEFINE,
+			Rhs:    assignStmt.Rhs,
+		}
+		suggested, err := render(pass.Fset, &suggestedStmt)
+
+		var fixes []analysis.SuggestedFix
+		if err == nil {
+			fixes = append(fixes, analysis.SuggestedFix{
+				Message: "replace `=` with `:=`",
+				TextEdits: []analysis.TextEdit{
+					{
+						Pos:     assignStmt.Pos(),
+						End:     assignStmt.End(),
+						NewText: []byte(suggested),
+					},
+				},
+			})
+		}
+
+		pass.Report(analysis.Diagnostic{
+			Pos:            assignStmt.Pos(),
+			Message:        "nested context in loop",
+			SuggestedFixes: fixes,
+		})
+
 	})
 
 	return nil, nil
@@ -113,6 +88,85 @@ func getBody(node ast.Node) (*ast.BlockStmt, error) {
 	return nil, errUnknown
 }
 
+func findNestedContext(pass *analysis.Pass, block *ast.BlockStmt, stmts []ast.Stmt) *ast.AssignStmt {
+	for _, stmt := range stmts {
+		// Recurse if necessary
+		if inner, ok := stmt.(*ast.BlockStmt); ok {
+			found := findNestedContext(pass, inner, inner.List)
+			if found != nil {
+				return found
+			}
+		}
+
+		if inner, ok := stmt.(*ast.IfStmt); ok {
+			found := findNestedContext(pass, inner.Body, inner.Body.List)
+			if found != nil {
+				return found
+			}
+		}
+
+		if inner, ok := stmt.(*ast.SwitchStmt); ok {
+			found := findNestedContext(pass, inner.Body, inner.Body.List)
+			if found != nil {
+				return found
+			}
+		}
+
+		if inner, ok := stmt.(*ast.CaseClause); ok {
+			found := findNestedContext(pass, block, inner.Body)
+			if found != nil {
+				return found
+			}
+		}
+
+		if inner, ok := stmt.(*ast.SelectStmt); ok {
+			found := findNestedContext(pass, inner.Body, inner.Body.List)
+			if found != nil {
+				return found
+			}
+		}
+
+		if inner, ok := stmt.(*ast.CommClause); ok {
+			found := findNestedContext(pass, block, inner.Body)
+			if found != nil {
+				return found
+			}
+		}
+
+		// Actually check for nested context
+		assignStmt, ok := stmt.(*ast.AssignStmt)
+		if !ok {
+			continue
+		}
+
+		t := pass.TypesInfo.TypeOf(assignStmt.Lhs[0])
+		if t == nil {
+			continue
+		}
+
+		if t.String() != "context.Context" {
+			continue
+		}
+
+		if assignStmt.Tok == token.DEFINE {
+			break
+		}
+
+		// allow assignment to non-pointer children of values defined within the loop
+		if lhs := getRootIdent(pass, assignStmt.Lhs[0]); lhs != nil {
+			if obj := pass.TypesInfo.ObjectOf(lhs); obj != nil {
+				if obj.Pos() >= block.Pos() && obj.Pos() < block.End() {
+					continue // definition is within the loop
+				}
+			}
+		}
+
+		return assignStmt
+	}
+
+	return nil
+}
+
 func getRootIdent(pass *analysis.Pass, node ast.Node) *ast.Ident {
 	for {
 		switch n := node.(type) {

testdata/src/example.go

@@ -25,12 +25,50 @@ func example() {
 		ctx = wrapContext(ctx) // want "nested context in loop"
 		break
 	}
+
+	// not fooled by shadowing in nested blocks
+	for {
+		err := doSomething()
+		if err != nil {
+			ctx := wrapContext(ctx)
+			ctx = wrapContext(ctx)
+		}
+
+		switch err {
+		case nil:
+			ctx := wrapContext(ctx)
+			ctx = wrapContext(ctx)
+		default:
+			ctx := wrapContext(ctx)
+			ctx = wrapContext(ctx)
+		}
+
+		{
+			ctx := wrapContext(ctx)
+			ctx = wrapContext(ctx)
+		}
+
+		select {
+		case <-ctx.Done():
+			ctx := wrapContext(ctx)
+			ctx = wrapContext(ctx)
+		default:
+		}
+
+		ctx = wrapContext(ctx) // want "nested context in loop"
+
+		break
+	}
 }
 
 func wrapContext(ctx context.Context) context.Context {
 	return context.WithoutCancel(ctx)
 }
 
+func doSomething() error {
+	return nil
+}
+
 // storing contexts in a struct isn't recommended, but local copies of a non-pointer struct should act like local copies of a context.
 func inStructs(ctx context.Context) {
 	for i := 0; i < 10; i++ {
@@ -71,3 +109,74 @@ func inStructs(ctx context.Context) {
 		rp[0].Ctx = context.WithValue(rp[0].Ctx, "other", "val")
 	}
 }
+
+func inVariousNestedBlocks(ctx context.Context) {
+	for {
+		err := doSomething()
+		if err != nil {
+			ctx = wrapContext(ctx) // want "nested context in loop"
+		}
+
+		break
+	}
+
+	for {
+		err := doSomething()
+		if err != nil {
+			if true {
+				ctx = wrapContext(ctx) // want "nested context in loop"
+			}
+		}
+
+		break
+	}
+
+	for {
+		err := doSomething()
+		switch err {
+		case nil:
+			ctx = wrapContext(ctx) // want "nested context in loop"
+		}
+
+		break
+	}
+
+	for {
+		err := doSomething()
+		switch err {
+		default:
+			ctx = wrapContext(ctx) // want "nested context in loop"
+		}
+
+		break
+	}
+
+	for {
+		ctx := wrapContext(ctx)
+
+		err := doSomething()
+		if err != nil {
+			ctx = wrapContext(ctx)
+		}
+
+		break
+	}
+
+	for {
+		{
+			ctx = wrapContext(ctx) // want "nested context in loop"
+		}
+
+		break
+	}
+
+	for {
+		select {
+		case <-ctx.Done():
+			ctx = wrapContext(ctx) // want "nested context in loop"
+		default:
+		}
+
+		break
+	}
+}