AppendInvoke: Merge test, real example (#48)

Follow up to #47 with the following changes.

- The tests for AppendInvoke with Close duplicate the tests for
  AppendInvoke. These can be merged, and the unit tests for Close only
  need to verify whether the Invoker returned by multierr.Close calls
  the Close function in the provided io.Closer.
- Replace AppendInvoke example with something more realistic.
- Update changelog.

CHANGELOG.md

@@ -1,6 +1,12 @@
 Releases
 ========
 
+v1.7.0 (unreleased)
+===================
+
+-   Add `AppendInvoke` to append into errors from `defer` blocks.
+
+
 v1.6.0 (2020-09-14)
 ===================
 

appendinvoke_example_test.go

@@ -0,0 +1,74 @@
+// Copyright (c) 2021 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package multierr_test
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+
+	"go.uber.org/multierr"
+)
+
+func ExampleAppendInvoke() {
+	if err := run(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func run() (err error) {
+	dir, err := ioutil.TempDir("", "multierr")
+	// We create a temporary directory and defer its deletion when this
+	// function returns.
+	//
+	// If we failed to delete the temporary directory, we append its
+	// failure into the returned value with multierr.AppendInvoke.
+	//
+	// This uses a custom invoker that we implement below.
+	defer multierr.AppendInvoke(&err, RemoveAll(dir))
+
+	path := filepath.Join(dir, "example.txt")
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	// Similarly, we defer closing the open file when the function returns,
+	// and appends its failure, if any, into the returned error.
+	//
+	// This uses the multierr.Close invoker included in multierr.
+	defer multierr.AppendInvoke(&err, multierr.Close(f))
+
+	if _, err := fmt.Fprintln(f, "hello"); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// RemoveAll is a multierr.Invoker that deletes the provided directory and all
+// of its contents.
+type RemoveAll string
+
+func (r RemoveAll) Invoke() error {
+	return os.RemoveAll(string(r))
+}

error_test.go

@@ -596,60 +596,49 @@ func TestAppendInvoke(t *testing.T) {
 				errors.New("baz"),
 			),
 		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.desc, func(t *testing.T) {
-			AppendInvoke(tt.into, tt.give)
-			assert.Equal(t, tt.want, *tt.into)
-		})
-	}
-}
-
-func TestAppendInvokeClose(t *testing.T) {
-	tests := []struct {
-		desc string
-		into *error
-		give error // error returned by Close()
-		want error
-	}{
 		{
-			desc: "append close nil into empty",
+			desc: "close/empty",
 			into: new(error),
-			give: nil,
-			want: nil,
+			give: Close(newCloserMock(t, errors.New("foo"))),
+			want: errors.New("foo"),
 		},
 		{
-			desc: "append close into non-empty, non-multierr",
-			into: errorPtr(errors.New("foo")),
-			give: errors.New("bar"),
-			want: Combine(
-				errors.New("foo"),
-				errors.New("bar"),
-			),
+			desc: "close/no fail",
+			into: new(error),
+			give: Close(newCloserMock(t, nil)),
+			want: nil,
 		},
 		{
-			desc: "append close into non-empty multierr",
-			into: errorPtr(Combine(
-				errors.New("foo"),
-				errors.New("bar"),
-			)),
-			give: errors.New("baz"),
+			desc: "close/non-empty",
+			into: errorPtr(errors.New("foo")),
+			give: Close(newCloserMock(t, errors.New("bar"))),
 			want: Combine(
 				errors.New("foo"),
 				errors.New("bar"),
-				errors.New("baz"),
 			),
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.desc, func(t *testing.T) {
-			closer := newCloserMock(t, tt.give)
-			AppendInvoke(tt.into, Close(closer))
+			AppendInvoke(tt.into, tt.give)
 			assert.Equal(t, tt.want, *tt.into)
 		})
 	}
 }
 
+func TestClose(t *testing.T) {
+	t.Run("fail", func(t *testing.T) {
+		give := errors.New("great sadness")
+		got := Close(newCloserMock(t, give)).Invoke()
+		assert.Same(t, give, got)
+	})
+
+	t.Run("success", func(t *testing.T) {
+		got := Close(newCloserMock(t, nil)).Invoke()
+		assert.Nil(t, got)
+	})
+}
+
 func TestAppendIntoNil(t *testing.T) {
 	t.Run("nil pointer panics", func(t *testing.T) {
 		assert.Panics(t, func() {
@@ -689,7 +678,6 @@ func newCloserMock(tb testing.TB, err error) io.Closer {
 			tb.Error("closerMock wasn't closed before test end")
 		}
 	})
-
 	return closerMock(func() error {
 		closed = true
 		return err

example_test.go

@@ -94,38 +94,6 @@ func ExampleAppendInto() {
 	// foo; baz
 }
 
-func ExampleAppendInvoke() {
-	var err error
-
-	var errFunc1 multierr.Invoker = multierr.Invoke(func() error {
-		fmt.Println("call 1 failed")
-		return errors.New("foo")
-	})
-
-	var errFunc2 multierr.Invoker = multierr.Invoke(func() error {
-		fmt.Println("call 2 did not fail")
-		return nil
-	})
-
-	var errFunc3 multierr.Invoker = multierr.Invoke(func() error {
-		fmt.Println("call 3 failed")
-		return errors.New("baz")
-	})
-
-	defer func() {
-		fmt.Println(err)
-	}()
-	defer multierr.AppendInvoke(&err, errFunc3)
-	defer multierr.AppendInvoke(&err, errFunc2)
-	defer multierr.AppendInvoke(&err, errFunc1)
-
-	// Output:
-	// call 1 failed
-	// call 2 did not fail
-	// call 3 failed
-	// foo; baz
-}
-
 type fakeCloser func() error
 
 func (f fakeCloser) Close() error {

go.mod

@@ -3,6 +3,7 @@ module go.uber.org/multierr
 go 1.14
 
 require (
-	github.com/stretchr/testify v1.3.0
+	github.com/stretchr/testify v1.7.0
 	go.uber.org/atomic v1.7.0
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )

go.sum

@@ -1,11 +1,16 @@
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 go.uber.org/atomic v1.7.0 h1:ADUqmZGgLDDfbSL9ZmPxKTybcoEYHgpYfELNoN+7hsw=
 go.uber.org/atomic v1.7.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=