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138 lines
3.3 KiB
138 lines
3.3 KiB
package rule
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import (
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"fmt"
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"go/ast"
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"github.com/mgechev/revive/lint"
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)
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// DeferRule lints unused params in functions.
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type DeferRule struct{}
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// Apply applies the rule to given file.
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func (r *DeferRule) Apply(file *lint.File, arguments lint.Arguments) []lint.Failure {
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allow := r.allowFromArgs(arguments)
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var failures []lint.Failure
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onFailure := func(failure lint.Failure) {
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failures = append(failures, failure)
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}
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w := lintDeferRule{onFailure: onFailure, allow: allow}
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ast.Walk(w, file.AST)
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return failures
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}
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// Name returns the rule name.
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func (r *DeferRule) Name() string {
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return "defer"
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}
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func (r *DeferRule) allowFromArgs(args lint.Arguments) map[string]bool {
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if len(args) < 1 {
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allow := map[string]bool{
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"loop": true,
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"call-chain": true,
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"method-call": true,
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"return": true,
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"recover": true,
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}
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return allow
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}
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aa, ok := args[0].([]interface{})
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if !ok {
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panic(fmt.Sprintf("Invalid argument '%v' for 'defer' rule. Expecting []string, got %T", args[0], args[0]))
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}
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allow := make(map[string]bool, len(aa))
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for _, subcase := range aa {
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sc, ok := subcase.(string)
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if !ok {
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panic(fmt.Sprintf("Invalid argument '%v' for 'defer' rule. Expecting string, got %T", subcase, subcase))
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}
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allow[sc] = true
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}
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return allow
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}
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type lintDeferRule struct {
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onFailure func(lint.Failure)
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inALoop bool
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inADefer bool
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inAFuncLit bool
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allow map[string]bool
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}
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func (w lintDeferRule) Visit(node ast.Node) ast.Visitor {
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switch n := node.(type) {
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case *ast.ForStmt:
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w.visitSubtree(n.Body, w.inADefer, true, w.inAFuncLit)
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return nil
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case *ast.RangeStmt:
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w.visitSubtree(n.Body, w.inADefer, true, w.inAFuncLit)
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return nil
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case *ast.FuncLit:
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w.visitSubtree(n.Body, w.inADefer, false, true)
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return nil
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case *ast.ReturnStmt:
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if len(n.Results) != 0 && w.inADefer && w.inAFuncLit {
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w.newFailure("return in a defer function has no effect", n, 1.0, "logic", "return")
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}
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case *ast.CallExpr:
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if isIdent(n.Fun, "recover") && !w.inADefer {
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// confidence is not 1 because recover can be in a function that is deferred elsewhere
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w.newFailure("recover must be called inside a deferred function", n, 0.8, "logic", "recover")
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}
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case *ast.DeferStmt:
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w.visitSubtree(n.Call.Fun, true, false, false)
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if w.inALoop {
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w.newFailure("prefer not to defer inside loops", n, 1.0, "bad practice", "loop")
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}
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switch fn := n.Call.Fun.(type) {
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case *ast.CallExpr:
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w.newFailure("prefer not to defer chains of function calls", fn, 1.0, "bad practice", "call-chain")
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case *ast.SelectorExpr:
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if id, ok := fn.X.(*ast.Ident); ok {
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isMethodCall := id != nil && id.Obj != nil && id.Obj.Kind == ast.Typ
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if isMethodCall {
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w.newFailure("be careful when deferring calls to methods without pointer receiver", fn, 0.8, "bad practice", "method-call")
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}
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}
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}
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return nil
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}
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return w
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}
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func (w lintDeferRule) visitSubtree(n ast.Node, inADefer, inALoop, inAFuncLit bool) {
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nw := &lintDeferRule{
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onFailure: w.onFailure,
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inADefer: inADefer,
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inALoop: inALoop,
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inAFuncLit: inAFuncLit,
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allow: w.allow}
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ast.Walk(nw, n)
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}
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func (w lintDeferRule) newFailure(msg string, node ast.Node, confidence float64, cat string, subcase string) {
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if !w.allow[subcase] {
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return
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}
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w.onFailure(lint.Failure{
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Confidence: confidence,
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Node: node,
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Category: cat,
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Failure: msg,
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})
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}
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