Print stack traces in more places

Author: msabramo

gomock/call.go

@@ -159,14 +159,17 @@ func (c *Call) Do(f interface{}) *Call {
 
 // Return declares the values to be returned by the mocked function call.
 func (c *Call) Return(rets ...interface{}) *Call {
+	skipFrames := 1
+
 	if h, ok := c.t.(testHelper); ok {
 		h.Helper()
 	}
 
 	mt := c.methodType
 	if len(rets) != mt.NumOut() {
-		c.t.Fatalf("wrong number of arguments to Return for %T.%v: got %d, want %d [%s]",
-			c.receiver, c.method, len(rets), mt.NumOut(), c.origin)
+		stackTraceStr := "\n\n" + currentStackTrace(skipFrames)
+		c.t.Fatalf("wrong number of arguments to Return for %T.%v: got %d, want %d [%s]%+v",
+			c.receiver, c.method, len(rets), mt.NumOut(), c.origin, stackTraceStr)
 	}
 	for i, ret := range rets {
 		if got, want := reflect.TypeOf(ret), mt.Out(i); got == want {
@@ -177,8 +180,9 @@ func (c *Call) Return(rets ...interface{}) *Call {
 			case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
 				// ok
 			default:
-				c.t.Fatalf("argument %d to Return for %T.%v is nil, but %v is not nillable [%s]",
-					i, c.receiver, c.method, want, c.origin)
+				stackTraceStr := "\n\n" + currentStackTrace(skipFrames)
+				c.t.Fatalf("argument %d to Return for %T.%v is nil, but %v is not nillable [%s]%+v",
+					i, c.receiver, c.method, want, c.origin, stackTraceStr)
 			}
 		} else if got.AssignableTo(want) {
 			// Assignable type relation. Make the assignment now so that the generated code
@@ -187,8 +191,10 @@ func (c *Call) Return(rets ...interface{}) *Call {
 			v.Set(reflect.ValueOf(ret))
 			rets[i] = v.Interface()
 		} else {
-			c.t.Fatalf("wrong type of argument %d to Return for %T.%v: %v is not assignable to %v [%s]",
-				i, c.receiver, c.method, got, want, c.origin)
+			skipFrames := 1
+			stackTraceStr := "\n\n" + currentStackTrace(skipFrames)
+			c.t.Fatalf("wrong type of argument %d to Return for %T.%v: %v is not assignable to %v [%s]%+v",
+				i, c.receiver, c.method, got, want, c.origin, stackTraceStr)
 		}
 	}
 
@@ -209,6 +215,8 @@ func (c *Call) Times(n int) *Call {
 // indirected through a pointer. Or, in the case of a slice, SetArg
 // will copy value's elements into the nth argument.
 func (c *Call) SetArg(n int, value interface{}) *Call {
+	skipFrames := 1
+
 	if h, ok := c.t.(testHelper); ok {
 		h.Helper()
 	}
@@ -217,8 +225,9 @@ func (c *Call) SetArg(n int, value interface{}) *Call {
 	// TODO: This will break on variadic methods.
 	// We will need to check those at invocation time.
 	if n < 0 || n >= mt.NumIn() {
-		c.t.Fatalf("SetArg(%d, ...) called for a method with %d args [%s]",
-			n, mt.NumIn(), c.origin)
+		stackTraceStr := "\n\n" + currentStackTrace(skipFrames)
+		c.t.Fatalf("SetArg(%d, ...) called for a method with %d args [%s]%+v",
+			n, mt.NumIn(), c.origin, stackTraceStr)
 	}
 	// Permit setting argument through an interface.
 	// In the interface case, we don't (nay, can't) check the type here.
@@ -227,16 +236,18 @@ func (c *Call) SetArg(n int, value interface{}) *Call {
 	case reflect.Ptr:
 		dt := at.Elem()
 		if vt := reflect.TypeOf(value); !vt.AssignableTo(dt) {
-			c.t.Fatalf("SetArg(%d, ...) argument is a %v, not assignable to %v [%s]",
-				n, vt, dt, c.origin)
+			stackTraceStr := "\n\n" + currentStackTrace(skipFrames)
+			c.t.Fatalf("SetArg(%d, ...) argument is a %v, not assignable to %v [%s]%+v",
+				n, vt, dt, c.origin, stackTraceStr)
 		}
 	case reflect.Interface:
 		// nothing to do
 	case reflect.Slice:
 		// nothing to do
 	default:
-		c.t.Fatalf("SetArg(%d, ...) referring to argument of non-pointer non-interface non-slice type %v [%s]",
-			n, at, c.origin)
+		stackTraceStr := "\n\n" + currentStackTrace(skipFrames)
+		c.t.Fatalf("SetArg(%d, ...) referring to argument of non-pointer non-interface non-slice type %v [%s]%+v",
+			n, at, c.origin, stackTraceStr)
 	}
 
 	c.addAction(func(args []interface{}) []interface{} {

gomock/controller.go

@@ -147,10 +147,9 @@ func (ctrl *Controller) Call(receiver interface{}, method string, args ...interf
 
 		expected, err := ctrl.expectedCalls.FindMatch(receiver, method, args)
 		if err != nil {
-			skipFrames := 2
 			origin := callerInfo(skipFrames)
-			stackTraceString := "\n\n" + stackTraceStringFromError(err, skipFrames)
-			ctrl.t.Fatalf("Unexpected call to %T.%v(%v) at %s because: %s%+v", receiver, method, args, origin, err, stackTraceString)
+			stackTraceStr := "\n\n" + stackTraceStringFromError(err, skipFrames)
+			ctrl.t.Fatalf("Unexpected call to %T.%v(%v) at %s because: %s%+v", receiver, method, args, origin, err, stackTraceStr)
 		}
 
 		// Two things happen here:
@@ -187,7 +186,9 @@ func (ctrl *Controller) Finish() {
 	defer ctrl.mu.Unlock()
 
 	if ctrl.finished {
-		ctrl.t.Fatalf("Controller.Finish was called more than once. It has to be called exactly once.")
+		skipFrames := 1
+		stackTraceStr := "\n\n" + currentStackTrace(skipFrames)
+		ctrl.t.Fatalf("Controller.Finish was called more than once. It has to be called exactly once.%+v", stackTraceStr)
 	}
 	ctrl.finished = true
 

gomock/stack.go

@@ -0,0 +1,43 @@
+package gomock
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+const skipFrames = 2
+
+type stackTracer interface {
+	StackTrace() errors.StackTrace
+}
+
+func stackTraceStringFromError(err error, skipFrames int) string {
+	if err, ok := err.(stackTracer); ok {
+		return stackTraceString(err.StackTrace(), skipFrames)
+	}
+	return ""
+}
+
+func currentStackTrace(skipFrames int) string {
+	err := errors.New("fake error just to get stack")
+	if err, ok := err.(stackTracer); ok {
+		return stackTraceString(err.StackTrace(), skipFrames)
+	}
+	return ""
+}
+
+func stackTraceString(stackTrace errors.StackTrace, skipFrames int) string {
+	buffer := bytes.NewBufferString("")
+	for i := skipFrames + 1; i < len(stackTrace); i++ {
+		frame := stackTrace[i]
+		buffer.WriteString(fmt.Sprintf("%+v\n", frame))
+		filename := fmt.Sprintf("%s", frame)
+		if strings.Contains(filename, "_test.go") {
+			break
+		}
+	}
+	return buffer.String()
+}