Show file and line number of call during errors

gomock/call.go

@@ -28,6 +28,7 @@ type Call struct {
 	method   string        // the name of the method
 	args     []Matcher     // the args
 	rets     []interface{} // the return values (if any)
+	origin   string        // file and line number of call setup
 
 	preReqs []*Call // prerequisite calls
 
@@ -78,8 +79,8 @@ func (c *Call) Do(f interface{}) *Call {
 func (c *Call) Return(rets ...interface{}) *Call {
 	mt := c.methodType()
 	if len(rets) != mt.NumOut() {
-		c.t.Fatalf("wrong number of arguments to Return for %T.%v: got %d, want %d",
-			c.receiver, c.method, 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)
 	}
 	for i, ret := range rets {
 		if got, want := reflect.TypeOf(ret), mt.Out(i); got == want {
@@ -90,8 +91,8 @@ 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",
-					i, c.receiver, c.method, want)
+				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)
 			}
 		} else if got.AssignableTo(want) {
 			// Assignable type relation. Make the assignment now so that the generated code
@@ -100,8 +101,8 @@ 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",
-				i, c.receiver, c.method, got, want)
+			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)
 		}
 	}
 
@@ -124,7 +125,8 @@ 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", n, mt.NumIn())
+		c.t.Fatalf("SetArg(%d, ...) called for a method with %d args [%s]",
+			n, mt.NumIn(), c.origin)
 	}
 	// Permit setting argument through an interface.
 	// In the interface case, we don't (nay, can't) check the type here.
@@ -133,12 +135,14 @@ 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", n, vt, dt)
+			c.t.Fatalf("SetArg(%d, ...) argument is a %v, not assignable to %v [%s]",
+				n, vt, dt, c.origin)
 		}
 	case reflect.Interface:
 		// nothing to do
 	default:
-		c.t.Fatalf("SetArg(%d, ...) referring to argument of non-pointer non-interface type %v", n, at)
+		c.t.Fatalf("SetArg(%d, ...) referring to argument of non-pointer non-interface type %v [%s]",
+			n, at, c.origin)
 	}
 	c.setArgs[n] = reflect.ValueOf(value)
 	return c
@@ -184,7 +188,7 @@ func (c *Call) String() string {
 		args[i] = arg.String()
 	}
 	arguments := strings.Join(args, ", ")
-	return fmt.Sprintf("%T.%v(%s)", c.receiver, c.method, arguments)
+	return fmt.Sprintf("%T.%v(%s) [%s]", c.receiver, c.method, arguments, c.origin)
 }
 
 // Tests if the given call matches the expected call.

gomock/controller.go

@@ -55,7 +55,11 @@
 //	- Handle different argument/return types (e.g. ..., chan, map, interface).
 package gomock
 
-import "sync"
+import (
+	"fmt"
+	"runtime"
+	"sync"
+)
 
 // A TestReporter is something that can be used to report test failures.
 // It is satisfied by the standard library's *testing.T.
@@ -98,7 +102,8 @@ func (ctrl *Controller) RecordCall(receiver interface{}, method string, args ...
 	ctrl.mu.Lock()
 	defer ctrl.mu.Unlock()
 
-	call := &Call{t: ctrl.t, receiver: receiver, method: method, args: margs, minCalls: 1, maxCalls: 1}
+	origin := callerInfo(2)
+	call := &Call{t: ctrl.t, receiver: receiver, method: method, args: margs, origin: origin, minCalls: 1, maxCalls: 1}
 
 	ctrl.expectedCalls.Add(call)
 	return call
@@ -110,7 +115,8 @@ func (ctrl *Controller) Call(receiver interface{}, method string, args ...interf
 
 	expected := ctrl.expectedCalls.FindMatch(receiver, method, args)
 	if expected == nil {
-		ctrl.t.Fatalf("no matching expected call: %T.%v(%v)", receiver, method, args)
+		origin := callerInfo(2)
+		ctrl.t.Fatalf("no matching expected call: %T.%v(%v) [%s]", receiver, method, args, origin)
 	}
 
 	// Two things happen here:
@@ -165,3 +171,10 @@ func (ctrl *Controller) Finish() {
 		ctrl.t.Fatalf("aborting test due to missing call(s)")
 	}
 }
+
+func callerInfo(skip int) string {
+	if _, file, line, ok := runtime.Caller(skip + 1); ok {
+		return fmt.Sprintf("%s:%d", file, line)
+	}
+	return "unknown file"
+}