1// Copyright 2021 The Bazel Authors. All rights reserved. 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14 15package main 16 17import ( 18 "bytes" 19 "context" 20 "fmt" 21 "os" 22 "os/exec" 23 "strings" 24) 25 26// runForError runs a command without showing its output. If the command fails, 27// runForError returns an error containing its stderr. 28func runForError(ctx context.Context, dir string, name string, args ...string) error { 29 stderr := &bytes.Buffer{} 30 cmd := exec.CommandContext(ctx, name, args...) 31 cmd.Env = envWithoutBazel() 32 cmd.Dir = dir 33 cmd.Stdout = nil 34 cmd.Stderr = stderr 35 err := cmd.Run() 36 return cleanCmdError(err, name, args, stderr.Bytes()) 37} 38 39// runForOutput runs a command and returns its output. If the command fails, 40// runForOutput returns an error containing its stderr. The command's output 41// is returned whether it failed or not. 42func runForOutput(ctx context.Context, dir string, name string, args ...string) ([]byte, error) { 43 stdout := &bytes.Buffer{} 44 stderr := &bytes.Buffer{} 45 cmd := exec.CommandContext(ctx, name, args...) 46 cmd.Env = envWithoutBazel() 47 cmd.Dir = dir 48 cmd.Stdout = stdout 49 cmd.Stderr = stderr 50 err := cmd.Run() 51 return stdout.Bytes(), cleanCmdError(err, name, args, stderr.Bytes()) 52} 53 54// envWithoutBazel runs the current process's environment without variables 55// starting with "BUILD_" added by 'bazel run'. These can confuse subprocesses. 56func envWithoutBazel() []string { 57 env := os.Environ() 58 filtered := make([]string, 0, len(env)) 59 for _, e := range env { 60 if strings.HasPrefix(e, "BUILD_") { 61 continue 62 } 63 filtered = append(filtered, e) 64 } 65 return filtered 66} 67 68// cleanCmdError wraps an error returned by exec.Cmd.Run with the command that 69// was run and its stderr output. 70func cleanCmdError(err error, name string, args []string, stderr []byte) error { 71 if err == nil { 72 return nil 73 } 74 return &commandError{ 75 argv: append([]string{name}, args...), 76 err: err, 77 } 78} 79 80type commandError struct { 81 argv []string 82 stderr []byte 83 err error 84} 85 86func (e *commandError) Error() string { 87 return fmt.Sprintf("running %s: %v\n%s", strings.Join(e.argv, " "), e.err, bytes.TrimSpace(e.stderr)) 88} 89 90func (e *commandError) Unwrap() error { 91 return e.err 92} 93