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