[CIT-678] Change error message to inform about new way to set device id (#572)

* Change error message to inform about new way to set device id.
* Fix tests for tedge config

Signed-off-by: Lukasz Woznicki <lukasz.woznicki@softwareag.com>

4 files changed, 30 insertions, 17 deletions

diff --git a/tedge_config/src/config_setting.rs b/tedge_config/src/config_setting.rs
index 3dcbfdab..aa68d66a 100644
--- a/tedge_config/src/config_setting.rs
+++ b/tedge_config/src/config_setting.rs
@@ -66,4 +66,10 @@ pub enum ConfigSettingError {
 
     #[error("Derivation for `{key}` failed: {cause}")]
     DerivationFailed { key: &'static str, cause: String },
+
+    #[error("Config value {key}, cannot be configured: {message} ")]
+    SettingIsNotConfigurable {
+        key: &'static str,
+        message: &'static str,
+    },
 }
diff --git a/tedge_config/src/settings.rs b/tedge_config/src/settings.rs
index e5cea255..b1a312e2 100644
--- a/tedge_config/src/settings.rs
+++ b/tedge_config/src/settings.rs
@@ -3,6 +3,7 @@ use crate::{config_setting::*, models::*};
 ///
 /// Identifier of the device within the fleet. It must be globally
 /// unique and the same one used in the device certificate.
+/// NOTE: This setting is derived from the device certificate and therefore is read only.
 ///
 /// Example: Raspberrypi-4d18303a-6d3a-11eb-b1a6-175f6bb72665")
 ///
@@ -14,8 +15,9 @@ impl ConfigSetting for DeviceIdSetting {
 
     const DESCRIPTION: &'static str = concat!(
         "Identifier of the device within the fleet. It must be ",
-        "globally unique and the same one used in the device certificate. ",
-        "Example: Raspberrypi-4d18303a-6d3a-11eb-b1a6-175f6bb72665"
+        "globally unique and is derived from the device certificate. ",
+        "Example: Raspberrypi-4d18303a-6d3a-11eb-b1a6-175f6bb72665",
+        "NOTE: This setting is derived from the device certificate and therefore is read only."
     );
 
     type Value = String;
diff --git a/tedge_config/src/tedge_config.rs b/tedge_config/src/tedge_config.rs
index dcc1ccb0..b4e88ce9 100644
--- a/tedge_config/src/tedge_config.rs
+++ b/tedge_config/src/tedge_config.rs
@@ -45,7 +45,12 @@ fn device_id_read_only_error() -> ConfigSettingError {
 fn cert_error_into_config_error(key: &'static str, err: CertificateError) -> ConfigSettingError {
     match &err {
         CertificateError::IoError(io_err) => match io_err.kind() {
-            std::io::ErrorKind::NotFound => ConfigSettingError::ConfigNotSet { key },
+            std::io::ErrorKind::NotFound => ConfigSettingError::SettingIsNotConfigurable { key,
+                message: concat!(
+                    "The device id is read from the device certificate.\n",
+                    "To set 'device.id' to some <id>, you can use `tedge cert create --device-id <id>`.",
+                ),
+            },
             _ => ConfigSettingError::DerivationFailed {
                 key,
                 cause: format!("{}", err),
diff --git a/tedge_config/tests/test_tedge_config.rs b/tedge_config/tests/test_tedge_config.rs
index a4f772e1..0cf4c396 100644
--- a/tedge_config/tests/test_tedge_config.rs
+++ b/tedge_config/tests/test_tedge_config.rs
@@ -38,7 +38,7 @@ external_keyfile = "key.pem"
     let config =
         TEdgeConfigRepository::new_with_defaults(config_location, config_defaults).load()?;
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
     assert_eq!(
         config.query(DeviceKeyPathSetting)?,
         FilePath::from("/path/to/key")
@@ -140,7 +140,7 @@ port = 1883
 
     {
         let mut config = config_repo.load()?;
-        assert!(config.query_optional(DeviceIdSetting)?.is_none());
+        assert!(config.query_optional(DeviceIdSetting).is_err());
         assert_eq!(
             config.query(DeviceKeyPathSetting)?,
             FilePath::from("/path/to/key")
@@ -204,7 +204,7 @@ port = 1883
     {
         let config = config_repo.load()?;
 
-        assert!(config.query_optional(DeviceIdSetting)?.is_none());
+        assert!(config.query_optional(DeviceIdSetting).is_err());
         assert_eq!(
             config.query(DeviceKeyPathSetting)?,
             FilePath::from("/path/to/key")
@@ -275,7 +275,7 @@ fn test_parse_config_with_only_device_configuration() -> Result<(), TEdgeConfigE
     let config =
         TEdgeConfigRepository::new_with_defaults(config_location, config_defaults).load()?;
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
     assert_eq!(
         config.query(DeviceCertPathSetting)?,
         FilePath::from("/etc/ssl/certs/tedge-certificate.pem")
@@ -320,7 +320,7 @@ url = "your-tenant.cumulocity.com"
     let config =
         TEdgeConfigRepository::new_with_defaults(config_location, config_defaults).load()?;
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
     assert_eq!(
         config.query(DeviceCertPathSetting)?,
         FilePath::from("/etc/ssl/certs/tedge-certificate.pem")
@@ -368,7 +368,7 @@ url = "MyAzure.azure-devices.net"
     let config =
         TEdgeConfigRepository::new_with_defaults(config_location, config_defaults).load()?;
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
     assert_eq!(
         config.query(DeviceCertPathSetting)?,
         FilePath::from("/etc/ssl/certs/tedge-certificate.pem")
@@ -416,7 +416,7 @@ port = 2222
     let config =
         TEdgeConfigRepository::new_with_defaults(config_location, config_defaults).load()?;
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
     assert_eq!(
         config.query(DeviceCertPathSetting)?,
         FilePath::from("/etc/ssl/certs/tedge-certificate.pem")
@@ -532,7 +532,7 @@ fn test_parse_config_empty_file() -> Result<(), TEdgeConfigError> {
     let config =
         TEdgeConfigRepository::new_with_defaults(config_location, config_defaults).load()?;
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
 
     assert_eq!(
         config.query(DeviceCertPathSetting)?,
@@ -565,7 +565,7 @@ fn test_parse_config_no_config_file() -> Result<(), TEdgeConfigError> {
     let config_location = TEdgeConfigLocation::from_custom_root("/non/existent/path");
     let config = TEdgeConfigRepository::new(config_location).load()?;
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
     assert_eq!(
         config.query(DeviceCertPathSetting)?,
         FilePath::from("/non/existent/path/device-certs/tedge-certificate.pem")
@@ -684,7 +684,7 @@ port = 1024
     let original_device_key_path = FilePath::from("/path/to/key");
     let original_device_cert_path = FilePath::from("/path/to/cert");
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
     assert_eq!(
         config.query(DeviceKeyPathSetting)?,
         original_device_key_path
@@ -723,7 +723,7 @@ port = 1024
     config.unset(AzureMapperTimestamp)?;
 
     let updated_mqtt_port = Port(2048);
-    config.update(MqttPortSetting, updated_mqtt_port.clone())?;
+    config.update(MqttPortSetting, updated_mqtt_port)?;
 
     assert_eq!(
         config.query(DeviceKeyPathSetting)?,
@@ -764,7 +764,7 @@ cert_path = "/path/to/cert"
         TEdgeConfigRepository::new_with_defaults(config_location, dummy_tedge_config_defaults())
             .load()?;
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
     Ok(())
 }
 
@@ -780,7 +780,7 @@ cert_path = "/path/to/cert"
         TEdgeConfigRepository::new_with_defaults(config_location, dummy_tedge_config_defaults())
             .load()?;
 
-    assert!(config.query_optional(DeviceIdSetting)?.is_none());
+    assert!(config.query_optional(DeviceIdSetting).is_err());
     Ok(())
 }
 
@@ -861,7 +861,7 @@ fn create_certificate(
         device_id,
     )?;
     let pem = keypair.certificate_pem_string()?;
-    let mut file = std::fs::File::create(path.clone())?;
+    let mut file = std::fs::File::create(path)?;
     file.write_all(pem.as_bytes())?;
     Ok(())
 }