1 files changed, 92 insertions, 0 deletions
diff --git a/internal/gocommand/invoke.go b/internal/gocommand/invoke.go
new file mode 100644
index 000000000..26cf7b18e
--- /dev/null
+++ b/internal/gocommand/invoke.go
@@ -0,0 +1,92 @@
+// Package gocommand is a helper for calling the go command.
+package gocommand
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+// An Invocation represents a call to the go command.
+type Invocation struct {
+	Verb       string
+	Args       []string
+	BuildFlags []string
+	Env        []string
+	WorkingDir string
+	Logf       func(format string, args ...interface{})
+}
+
+// Run runs the invocation, returning its stdout and an error suitable for
+// human consumption, including stderr.
+func (i *Invocation) Run(ctx context.Context) (*bytes.Buffer, error) {
+	stdout, _, friendly, _ := i.RunRaw(ctx)
+	return stdout, friendly
+}
+
+// RunRaw is like Run, but also returns the raw stderr and error for callers
+// that want to do low-level error handling/recovery.
+func (i *Invocation) RunRaw(ctx context.Context) (stdout *bytes.Buffer, stderr *bytes.Buffer, friendlyError error, rawError error) {
+	log := i.Logf
+	if log == nil {
+		log = func(string, ...interface{}) {}
+	}
+
+	goArgs := []string{i.Verb}
+	switch i.Verb {
+	case "mod":
+		// mod needs the sub-verb before build flags.
+		goArgs = append(goArgs, i.Args[0])
+		goArgs = append(goArgs, i.BuildFlags...)
+		goArgs = append(goArgs, i.Args[1:]...)
+	case "env":
+		// env doesn't take build flags.
+		goArgs = append(goArgs, i.Args...)
+	default:
+		goArgs = append(goArgs, i.BuildFlags...)
+		goArgs = append(goArgs, i.Args...)
+	}
+	cmd := exec.CommandContext(ctx, "go", goArgs...)
+	stdout = &bytes.Buffer{}
+	stderr = &bytes.Buffer{}
+	cmd.Stdout = stdout
+	cmd.Stderr = stderr
+	// On darwin the cwd gets resolved to the real path, which breaks anything that
+	// expects the working directory to keep the original path, including the
+	// go command when dealing with modules.
+	// The Go stdlib has a special feature where if the cwd and the PWD are the
+	// same node then it trusts the PWD, so by setting it in the env for the child
+	// process we fix up all the paths returned by the go command.
+	cmd.Env = append(append([]string{}, i.Env...), "PWD="+i.WorkingDir)
+	cmd.Dir = i.WorkingDir
+
+	defer func(start time.Time) { log("%s for %v", time.Since(start), cmdDebugStr(cmd)) }(time.Now())
+
+	rawError = cmd.Run()
+	friendlyError = rawError
+	if rawError != nil {
+		// Check for 'go' executable not being found.
+		if ee, ok := rawError.(*exec.Error); ok && ee.Err == exec.ErrNotFound {
+			friendlyError = fmt.Errorf("go command required, not found: %v", ee)
+		}
+		if ctx.Err() != nil {
+			friendlyError = ctx.Err()
+		}
+		friendlyError = fmt.Errorf("err: %v: stderr: %s", rawError, stderr)
+	}
+	return
+}
+
+func cmdDebugStr(cmd *exec.Cmd) string {
+	env := make(map[string]string)
+	for _, kv := range cmd.Env {
+		split := strings.Split(kv, "=")
+		k, v := split[0], split[1]
+		env[k] = v
+	}
+
+	return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v GOPROXY=%v PWD=%v go %v", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["GOPROXY"], env["PWD"], cmd.Args)
+}