Init commit

Author: earthboundkid

code.go

@@ -0,0 +1,62 @@
+package exitcode
+
+import (
+	"flag"
+	"os"
+
+	"golang.org/x/xerrors"
+)
+
+// Coder is an interface to control what value Get returns.
+type Coder interface {
+	error
+	ExitCode() int
+}
+
+// Get gets the exit code associated with an error. Cases:
+//
+// nil => 0
+// errors implementing Coder => value returned by ExitCode
+// flag.ErrHelp => 2
+// all other errors => 1
+func Get(err error) int {
+	if err == nil {
+		return 0
+	}
+
+	if coder := Coder(nil); xerrors.As(err, &coder) {
+		return coder.ExitCode()
+	}
+
+	if xerrors.Is(err, flag.ErrHelp) {
+		return 2
+	}
+
+	return 1
+}
+
+// Set wraps an error in a Coder, setting its error code.
+func Set(err error, code int) error {
+	return coder{err, code}
+}
+
+var _ Coder = coder{}
+
+type coder struct {
+	error
+	int
+}
+
+func (co coder) ExitCode() int {
+	return co.int
+}
+
+func (co coder) Unwrap() error {
+	return co.error
+}
+
+// Exit is a convenience function that calls os.Exit
+// with the exit code associated with err.
+func Exit(err error) {
+	os.Exit(Get(err))
+}

code_test.go

@@ -0,0 +1,57 @@
+package exitcode_test
+
+import (
+	"errors"
+	"flag"
+	"testing"
+
+	"github.com/carlmjohnson/exitcode"
+	"golang.org/x/xerrors"
+)
+
+func TestGet(t *testing.T) {
+	base := exitcode.Set(errors.New(""), 4)
+	wrapped := xerrors.Errorf("wrapping: %w", base)
+
+	testCases := map[string]struct {
+		error
+		int
+	}{
+		"nil":     {nil, 0},
+		"default": {errors.New(""), 1},
+		"help":    {flag.ErrHelp, 2},
+		"set":     {exitcode.Set(errors.New(""), 3), 3},
+		"wrapped": {wrapped, 4},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			err := tc.error
+			want := tc.int
+			got := exitcode.Get(err)
+			if got != want {
+				t.Errorf("%v: %d != %d", err, got, want)
+			}
+		})
+	}
+}
+
+func TestSet(t *testing.T) {
+	t.Run("same-message", func(t *testing.T) {
+		err := xerrors.New("hello")
+		coder := exitcode.Set(err, 2)
+		got := err.Error()
+		want := coder.Error()
+		if got != want {
+			t.Errorf("error message %q != %q", got, want)
+		}
+	})
+	t.Run("keep-chain", func(t *testing.T) {
+		err := xerrors.New("hello")
+		coder := exitcode.Set(err, 3)
+
+		if !xerrors.Is(coder, err) {
+			t.Errorf("broken chain: %v is not %v", coder, err)
+		}
+	})
+}

go.mod

@@ -0,0 +1,5 @@
+module github.com/carlmjohnson/exitcode
+
+go 1.12
+
+require golang.org/x/xerrors v0.0.0-20190513163551-3ee3066db522

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/xerrors v0.0.0-20190513163551-3ee3066db522 h1:bhOzK9QyoD0ogCnFro1m2mz41+Ib0oOhfJnBp5MR4K4=
+golang.org/x/xerrors v0.0.0-20190513163551-3ee3066db522/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=