adds support for control exit statements

rule/unconditional-recursion.go

@@ -53,35 +53,15 @@ type lintUnconditionalRecursionRule struct {
 	currentFunc *funcStatus
 }
 
+// Visit will traverse the file AST.
+// The rule is based in the following algorithm: inside each function body we search for calls to the function itself.
+// We do not search inside conditional control structures (if, for, switch, ...) because any recursive call inside them is conditioned
+// We do search inside conditional control structures are statements that will take the control out of the function (return, exit, panic)
+// If we find conditional control exits, it means the function is NOT unconditionally-recursive
+// If we find a recursive call before finding any conditional exit, a failure is generated
+// In resume: if we found a recursive call control-dependant from the entry point of the function then we raise a failure.
 func (w lintUnconditionalRecursionRule) Visit(node ast.Node) ast.Visitor {
 	switch n := node.(type) {
-	case *ast.IfStmt:
-		w.updateFuncStatus(n.Body)
-		w.updateFuncStatus(n.Else)
-		return nil
-	case *ast.SelectStmt:
-		w.updateFuncStatus(n.Body)
-		return nil
-	case *ast.RangeStmt:
-		w.updateFuncStatus(n.Body)
-		return nil
-	case *ast.TypeSwitchStmt:
-		w.updateFuncStatus(n.Body)
-		return nil
-	case *ast.SwitchStmt:
-		w.updateFuncStatus(n.Body)
-		return nil
-	case *ast.GoStmt:
-		for _, a := range n.Call.Args {
-			ast.Walk(w, a) // check if arguments have a recursive call
-		}
-		return nil // recursive async call is not an issue
-	case *ast.ForStmt:
-		if n.Cond != nil {
-			return nil
-		}
-		// unconditional loop
-		return w
 	case *ast.FuncDecl:
 		var rec *ast.Ident
 		switch {
@@ -120,6 +100,33 @@ func (w lintUnconditionalRecursionRule) Visit(node ast.Node) ast.Visitor {
 				Failure:    "unconditional recursive call",
 			})
 		}
+	case *ast.IfStmt:
+		w.updateFuncStatus(n.Body)
+		w.updateFuncStatus(n.Else)
+		return nil
+	case *ast.SelectStmt:
+		w.updateFuncStatus(n.Body)
+		return nil
+	case *ast.RangeStmt:
+		w.updateFuncStatus(n.Body)
+		return nil
+	case *ast.TypeSwitchStmt:
+		w.updateFuncStatus(n.Body)
+		return nil
+	case *ast.SwitchStmt:
+		w.updateFuncStatus(n.Body)
+		return nil
+	case *ast.GoStmt:
+		for _, a := range n.Call.Args {
+			ast.Walk(w, a) // check if arguments have a recursive call
+		}
+		return nil // recursive async call is not an issue
+	case *ast.ForStmt:
+		if n.Cond != nil {
+			return nil
+		}
+		// unconditional loop
+		return w
 	}
 
 	return w
@@ -133,11 +140,48 @@ func (w *lintUnconditionalRecursionRule) updateFuncStatus(node ast.Node) {
 	w.currentFunc.seenConditionalExit = w.hasControlExit(node)
 }
 
+var exitFunctions = map[string]map[string]bool{
+	"os":      map[string]bool{"Exit": true},
+	"syscall": map[string]bool{"Exit": true},
+	"log": map[string]bool{
+		"Fatal":   true,
+		"Fatalf":  true,
+		"Fatalln": true,
+		"Panic":   true,
+		"Panicf":  true,
+		"Panicln": true,
+	},
+}
+
 func (w *lintUnconditionalRecursionRule) hasControlExit(node ast.Node) bool {
-	filter := func(n ast.Node) bool {
-		_, ok := n.(*ast.ReturnStmt)
-		return ok
+	// isExit returns true if the given node makes control exit the function
+	isExit := func(node ast.Node) bool {
+		switch n := node.(type) {
+		case *ast.ReturnStmt:
+			return true
+		case *ast.CallExpr:
+			if isIdent(n.Fun, "panic") {
+				return true
+			}
+			se, ok := n.Fun.(*ast.SelectorExpr)
+			if !ok {
+				return false
+			}
+
+			id, ok := se.X.(*ast.Ident)
+			if !ok {
+				return false
+			}
+
+			fn := se.Sel.Name
+			pkg := id.Name
+			if exitFunctions[pkg] != nil && exitFunctions[pkg][fn] { // it's a call to an exit function
+				return true
+			}
+		}
+
+		return false
 	}
 
-	return len(pick(node, filter, nil)) != 0
+	return len(pick(node, isExit, nil)) != 0
 }