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- // Copyright 2016 Google LLC
- //
- // Licensed under the Apache License, Version 2.0 (the "License");
- // you may not use this file except in compliance with the License.
- // You may obtain a copy of the License at
- //
- // http://www.apache.org/licenses/LICENSE-2.0
- //
- // Unless required by applicable law or agreed to in writing, software
- // distributed under the License is distributed on an "AS IS" BASIS,
- // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- // See the License for the specific language governing permissions and
- // limitations under the License.
-
- package pretty
-
- import (
- "fmt"
- "io/ioutil"
- "os"
- "os/exec"
- "syscall"
- )
-
- // Diff compares the pretty-printed representation of two values. The second
- // return value reports whether the two values' representations are identical.
- // If it is false, the first return value contains the diffs.
- //
- // The output labels the first value "want" and the second "got".
- //
- // Diff works by invoking the "diff" command. It will only succeed in
- // environments where "diff" is on the shell path.
- func Diff(want, got interface{}) (string, bool, error) {
- fname1, err := writeToTemp(want)
- if err != nil {
- return "", false, err
- }
- defer os.Remove(fname1)
-
- fname2, err := writeToTemp(got)
- if err != nil {
- return "", false, err
- }
- defer os.Remove(fname2)
-
- cmd := exec.Command("diff", "-u", "--label=want", "--label=got", fname1, fname2)
- out, err := cmd.Output()
- if err == nil {
- return string(out), true, nil
- }
- eerr, ok := err.(*exec.ExitError)
- if !ok {
- return "", false, err
- }
- ws, ok := eerr.Sys().(syscall.WaitStatus)
- if !ok {
- return "", false, err
- }
- if ws.ExitStatus() != 1 {
- return "", false, err
- }
- // Exit status of 1 means no error, but diffs were found.
- return string(out), false, nil
- }
-
- func writeToTemp(v interface{}) (string, error) {
- f, err := ioutil.TempFile("", "prettyDiff")
- if err != nil {
- return "", err
- }
- if _, err := fmt.Fprintf(f, "%+v\n", Value(v)); err != nil {
- return "", err
- }
- if err := f.Close(); err != nil {
- return "", err
- }
- return f.Name(), nil
- }
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