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mock: Allow custom matcher functions to return error strings displayed on a failed match #781

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mock: Allow custom matcher functions to return error strings displayed on a failed match #781

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b59ea01
Allow custom matcher functions to return error strings displayed on a…
brandonbodnar-wk Jul 19, 2018
42afde4
Introduce unexported match method to report errors matching
brandonbodnar-wk Sep 17, 2018
3cd4cbe
Fix example codeblock spacing
brandonbodnar-wk Sep 17, 2018
b812942
Merge remote-tracking branch 'origin/master' into allow-error-string-…
brandonbodnar-wk May 28, 2019
30f794c
Merge remote-tracking branch 'origin/master' into allow-error-string-…
brandonbodnar-wk May 28, 2019
1032e82
Merge branch 'master' into allow-error-string-from-custom-matcher
georgelesica-wf Jul 9, 2019
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60 changes: 48 additions & 12 deletions mock/mock.go
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Original file line number Diff line number Diff line change
Expand Up @@ -557,6 +557,10 @@ const (
Anything = "mock.Anything"
)

var (
errorType = reflect.TypeOf((*error)(nil)).Elem()
)

// AnythingOfTypeArgument is a string that contains the type of an argument
// for use when type checking. Used in Diff and Assert.
type AnythingOfTypeArgument string
Expand All @@ -578,6 +582,10 @@ type argumentMatcher struct {
}

func (f argumentMatcher) Matches(argument interface{}) bool {
return f.match(argument) == nil
}

func (f argumentMatcher) match(argument interface{}) error {
expectType := f.fn.Type().In(0)
expectTypeNilSupported := false
switch expectType.Kind() {
Expand All @@ -598,25 +606,52 @@ func (f argumentMatcher) Matches(argument interface{}) bool {
}
if argType == nil || argType.AssignableTo(expectType) {
result := f.fn.Call([]reflect.Value{arg})
return result[0].Bool()

var matchError error
switch {
case result[0].Type().Kind() == reflect.Bool:
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Would it make the code simpler if we changed to if ... else if ... else if ... else here? Reason being that 'target-less' switch statements aren't obvious in their order of execution if there is more than 1 possible match.

if !result[0].Bool() {
matchError = fmt.Errorf("not matched by %s", f)
}
case result[0].Type().Implements(errorType):
if !result[0].IsNil() {
matchError = result[0].Interface().(error)
}
default:
panic(fmt.Errorf("matcher function of unknown type: %s", result[0].Type().Kind()))
}

return matchError
}
return false
return fmt.Errorf("unexpected type for %s", f)
}

func (f argumentMatcher) String() string {
return fmt.Sprintf("func(%s) bool", f.fn.Type().In(0).Name())
return fmt.Sprintf("func(%s) %s", f.fn.Type().In(0).String(), f.fn.Type().Out(0).String())
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Won't the %s formatting directives have the same effect as calling .String() on the input arguments, by definition?

}

func (f argumentMatcher) GoString() string {
return fmt.Sprintf("MatchedBy(%s)", f)
}

// MatchedBy can be used to match a mock call based on only certain properties
// from a complex struct or some calculation. It takes a function that will be
// evaluated with the called argument and will return true when there's a match
// and false otherwise.
// evaluated with the called argument and will return either a boolean (true
// when there's a match and false otherwise) or an error (nil when there's a
// match and error holding the failure message otherwise).
//
// Examples:
// m.On("Do", MatchedBy(func(req *http.Request) bool { return req.Host == "example.com" }))
//
// Example:
// m.On("Do", MatchedBy(func(req *http.Request) bool { return req.Host == "example.com" }))
// m.On("Do", MatchedBy(func(req *http.Request) (err error) {
// if req.Host != "example.com" {
// err = errors.New("host was not example.com")
// }
// return
// })
//
// |fn|, must be a function accepting a single argument (of the expected type)
// which returns a bool. If |fn| doesn't match the required signature,
// which returns a bool or error. If |fn| doesn't match the required signature,
// MatchedBy() panics.
func MatchedBy(fn interface{}) argumentMatcher {
fnType := reflect.TypeOf(fn)
Expand All @@ -627,8 +662,9 @@ func MatchedBy(fn interface{}) argumentMatcher {
if fnType.NumIn() != 1 {
panic(fmt.Sprintf("assert: arguments: %s does not take exactly one argument", fn))
}
if fnType.NumOut() != 1 || fnType.Out(0).Kind() != reflect.Bool {
panic(fmt.Sprintf("assert: arguments: %s does not return a bool", fn))

if fnType.NumOut() != 1 || (fnType.Out(0).Kind() != reflect.Bool && !fnType.Out(0).Implements(errorType)) {
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Would the code be simpler if we extract this into its own method? Something like returnsBoolOrError()? We can then also add a few good unit tests focusing just on it.

panic(fmt.Sprintf("assert: arguments: %s does not return a bool or a error", fn))
}

return argumentMatcher{fn: reflect.ValueOf(fn)}
Expand Down Expand Up @@ -688,11 +724,11 @@ func (args Arguments) Diff(objects []interface{}) (string, int) {
}

if matcher, ok := expected.(argumentMatcher); ok {
if matcher.Matches(actual) {
if matchError := matcher.match(actual); matchError == nil {
output = fmt.Sprintf("%s\t%d: PASS: %s matched by %s\n", output, i, actualFmt, matcher)
} else {
differences++
output = fmt.Sprintf("%s\t%d: FAIL: %s not matched by %s\n", output, i, actualFmt, matcher)
output = fmt.Sprintf("%s\t%d: FAIL: %s %s\n", output, i, actualFmt, matchError)
}
} else if reflect.TypeOf(expected) == reflect.TypeOf((*AnythingOfTypeArgument)(nil)).Elem() {

Expand Down
29 changes: 27 additions & 2 deletions mock/mock_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1259,7 +1259,7 @@ func Test_Arguments_Diff_WithArgMatcher(t *testing.T) {

diff, count = args.Diff([]interface{}{"string", false, true})
assert.Equal(t, 1, count)
assert.Contains(t, diff, `(bool=false) not matched by func(int) bool`)
assert.Contains(t, diff, `(bool=false) unexpected type for func(int) bool`)

diff, count = args.Diff([]interface{}{"string", 123, false})
assert.Contains(t, diff, `(int=123) matched by func(int) bool`)
Expand All @@ -1269,6 +1269,31 @@ func Test_Arguments_Diff_WithArgMatcher(t *testing.T) {
assert.Contains(t, diff, `No differences.`)
}

func Test_Arguments_Diff_WithArgMatcherReturningError(t *testing.T) {
matchFn := func(a int) (err error) {
if a != 123 {
err = errors.New("did not match")
}
return
}
var args = Arguments([]interface{}{"string", MatchedBy(matchFn), true})

diff, count := args.Diff([]interface{}{"string", 124, true})
assert.Equal(t, 1, count)
assert.Contains(t, diff, `(int=124) did not match`)

diff, count = args.Diff([]interface{}{"string", false, true})
assert.Equal(t, 1, count)
assert.Contains(t, diff, `(bool=false) unexpected type for func(int) error`)

diff, count = args.Diff([]interface{}{"string", 123, false})
assert.Contains(t, diff, `(int=123) matched by func(int) error`)

diff, count = args.Diff([]interface{}{"string", 123, true})
assert.Equal(t, 0, count)
assert.Contains(t, diff, `No differences.`)
}

func Test_Arguments_Assert(t *testing.T) {

var args = Arguments([]interface{}{"string", 123, true})
Expand Down Expand Up @@ -1445,7 +1470,7 @@ func TestArgumentMatcherToPrintMismatch(t *testing.T) {
defer func() {
if r := recover(); r != nil {
matchingExp := regexp.MustCompile(
`\s+mock: Unexpected Method Call\s+-*\s+GetTime\(int\)\s+0: 1\s+The closest call I have is:\s+GetTime\(mock.argumentMatcher\)\s+0: mock.argumentMatcher\{.*?\}\s+Diff:.*\(int=1\) not matched by func\(int\) bool`)
`\s+mock: Unexpected Method Call\s+-*\s+GetTime\(int\)\s+0: 1\s+The closest call I have is:\s+GetTime\(mock.argumentMatcher\)\s+0: MatchedBy\(func\(int\) bool\)\s+Diff:.*\(int=1\) not matched by func\(int\) bool`)
assert.Regexp(t, matchingExp, r)
}
}()
Expand Down