fix empty previous output (#84)

Author: rucciva

shell/resource_shell_script.go

@@ -259,7 +259,8 @@ func read(d *schema.ResourceData, meta interface{}, stack []Action) error {
 	sensitiveEnvironment := formatEnvironmentVariables(sensitiveEnvVariables)
 	interpreter := getInterpreter(client, d)
 	workingDirectory := d.Get("working_directory").(string)
-	previousOutput := expandOutput(d.Get("output"))
+	o, _ := d.GetChange("output")
+	previousOutput := expandOutput(o)
 	enableParallelism := client.config.EnableParallelism
 
 	commandConfig := &CommandConfig{
@@ -346,7 +347,8 @@ func update(d *schema.ResourceData, meta interface{}, stack []Action) error {
 	sensitiveEnvironment := formatEnvironmentVariables(sensitiveEnvVariables)
 	interpreter := getInterpreter(client, d)
 	workingDirectory := d.Get("working_directory").(string)
-	previousOutput := expandOutput(d.Get("output"))
+	o, _ := d.GetChange("output")
+	previousOutput := expandOutput(o)
 	enableParallelism := client.config.EnableParallelism
 
 	commandConfig := &CommandConfig{
@@ -395,7 +397,8 @@ func delete(d *schema.ResourceData, meta interface{}, stack []Action) error {
 	sensitiveEnvironment := formatEnvironmentVariables(sensitiveEnvVariables)
 	interpreter := getInterpreter(client, d)
 	workingDirectory := d.Get("working_directory").(string)
-	previousOutput := expandOutput(d.Get("output"))
+	o, _ := d.GetChange("output")
+	previousOutput := expandOutput(o)
 	enableParallelism := client.config.EnableParallelism
 
 	commandConfig := &CommandConfig{

shell/resource_shell_script_test.go

@@ -504,3 +504,62 @@ func testAccShellShellScriptConfig_outputDependency(filename string, value bool,
 	}
 	return
 }
+
+func TestAccShellShellScript_previousOutput(t *testing.T) {
+	file := "/tmp/test-file-" + acctest.RandString(16)
+	resource.Test(t, resource.TestCase{
+		Providers: testAccProviders,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccShellShellScriptConfig_previousOutput(file, true),
+				Check:  resource.TestCheckResourceAttr("shell_script.previous", "output.value", ""),
+			},
+			{
+				Config: testAccShellShellScriptConfig_previousOutput(file, false),
+				Check:  resource.TestCheckResourceAttr("shell_script.previous", "output.value", "true"),
+			},
+		},
+	})
+}
+
+func testAccShellShellScriptConfig_previousOutput(filename string, value bool) (conf string) {
+	return fmt.Sprintf(`
+		resource "shell_script" "shell_script" {
+			lifecycle_commands {
+				create = <<-EOF
+					echo -n '{"value": '"$VALUE"'}' > "$FILE"
+				EOF
+				read = <<-EOF
+					cat "$FILE"
+				EOF
+				update = <<-EOF
+					cat > "$FILE.previous" && echo -n '{"value": '"$VALUE"'}' > "$FILE"
+				EOF
+				delete = <<-EOF
+					rm "$FILE"
+				EOF
+			}
+			environment = {
+				FILE = "%s"
+				VALUE = "%t"
+			}
+		}
+
+		resource "shell_script" "previous" {
+			lifecycle_commands {
+				create = "true"
+				read = <<-EOF
+					cat $FILE || echo -n '{"value": null}'
+				EOF 
+				update = "true"
+				delete = "true"
+			}
+			environment = {
+				FILE = "${shell_script.shell_script.environment.FILE}.previous"
+			}
+			triggers = {
+				VALUE = shell_script.shell_script.environment.VALUE
+			}
+		}
+	`, filename, value)
+}