Allow executor to append environment variables

main.go

@@ -17,6 +17,8 @@ func main() {
 	log.Printf("[INFO] CLI args: %#v", os.Args)
 
 	e := tfexec.NewExecutor("tmp/test", os.Environ())
+	e.AppendEnv("TF_LOG", "TRACE")
+	e.AppendEnv("DIRENV_LOG_FORMAT", "")
 	terraformCLI := tfexec.NewTerraformCLI(e)
 	terraformCLI.SetExecPath("direnv exec . terraform")
 	v, err := terraformCLI.Version(context.Background())

tfexec/executor.go

@@ -17,6 +17,8 @@ type Executor interface {
 	NewCommandContext(ctx context.Context, name string, args ...string) (Command, error)
 	// Run executes a command.
 	Run(cmd Command) error
+	// AppendEnv appends an environment variable.
+	AppendEnv(key string, value string)
 }
 
 // executor impolements the Executor interface.
@@ -77,3 +79,8 @@ func (e *executor) Run(cmd Command) error {
 	}
 	return nil
 }
+
+// AppendEnv appends an environment variable.
+func (e *executor) AppendEnv(key string, value string) {
+	e.env = append(e.env, key+"="+value)
+}

tfexec/executor_test.go

@@ -104,24 +104,38 @@ func TestExecutorRun(t *testing.T) {
 
 func TestExecutorEnv(t *testing.T) {
 	cases := []struct {
-		desc string
-		args []string
-		env  []string
-		want string
-		ok   bool
+		desc        string
+		args        []string
+		env         []string
+		appendKey   string
+		appendValue string
+		want        string
+		ok          bool
 	}{
 		{
-			desc: "test set env",
+			desc: "test set env with NewExecutor",
 			args: []string{"/bin/sh", "-c", "echo $FOO"},
 			env:  []string{"FOO=foo"},
 			want: "foo\n",
 			ok:   true,
 		},
+		{
+			desc:        "test set env with AppendEnv",
+			args:        []string{"/bin/sh", "-c", "echo $FOO $BAR"},
+			env:         []string{"FOO=foo"},
+			appendKey:   "BAR",
+			appendValue: "bar",
+			want:        "foo bar\n",
+			ok:          true,
+		},
 	}
 
 	for _, tc := range cases {
 		t.Run(tc.desc, func(t *testing.T) {
 			e := NewExecutor(".", tc.env)
+			if len(tc.appendKey) > 0 {
+				e.AppendEnv(tc.appendKey, tc.appendValue)
+			}
 			cmd, err := e.NewCommandContext(context.Background(), tc.args[0], tc.args[1:]...)
 			if err != nil {
 				t.Fatalf("failed to NewCommandContext: %s", err)

tfexec/mock.go

@@ -56,6 +56,11 @@ func (e *mockExecutor) Run(cmd Command) error {
 	return cmd.Run()
 }
 
+// AppendEnv appends an environment variable.
+func (e *mockExecutor) AppendEnv(key string, value string) {
+	// no op.
+}
+
 // mockRunFunc is a type for callback of mockCommand.Run() to allow us to cause side effects.
 type mockRunFunc func(args ...string) error