Improve exception message: include value of object that caused the failure

Author: mtoffl01

internal-api/src/main/java/datadog/trace/bootstrap/config/provider/stableconfig/Rule.java

@@ -32,7 +32,10 @@ public static Rule from(Map<?, ?> map) {
     }
     if (!(selectorsObj instanceof List)) {
       throw new StableConfigMappingException(
-          "'selectors' must be a list, but got: " + selectorsObj.getClass().getSimpleName());
+          "'selectors' must be a list, but got: "
+              + selectorsObj.getClass().getSimpleName()
+              + ", value: "
+              + StableConfigMappingException.safeToString(selectorsObj));
     }
     List<Selector> selectors =
         unmodifiableList(
@@ -43,7 +46,10 @@ public static Rule from(Map<?, ?> map) {
                         s -> {
                           if (!(s instanceof Map)) {
                             throw new StableConfigMappingException(
-                                "Selector must be a map, but got: " + s.getClass().getSimpleName());
+                                "Each selector must be a map, but got: "
+                                    + s.getClass().getSimpleName()
+                                    + ", value: "
+                                    + StableConfigMappingException.safeToString(s));
                           }
                           return Selector.from((Map<?, ?>) s);
                         })
@@ -55,7 +61,10 @@ public static Rule from(Map<?, ?> map) {
     }
     if (!(configObj instanceof Map)) {
       throw new StableConfigMappingException(
-          "'configuration' must be a map, but got: " + configObj.getClass().getSimpleName());
+          "'configuration' must be a map, but got: "
+              + configObj.getClass().getSimpleName()
+              + ", value: "
+              + StableConfigMappingException.safeToString(configObj));
     }
     Map<String, Object> configuration = (Map<String, Object>) configObj;
 

internal-api/src/main/java/datadog/trace/bootstrap/config/provider/stableconfig/Selector.java

@@ -24,7 +24,10 @@ public static Selector from(Map<?, ?> map) {
     }
     if (!(originObj instanceof String)) {
       throw new StableConfigMappingException(
-          "'origin' must be a string, but got: " + originObj.getClass().getSimpleName());
+          "'origin' must be a string, but got: "
+              + originObj.getClass().getSimpleName()
+              + ", value: "
+              + StableConfigMappingException.safeToString(originObj));
     }
     String origin = (String) originObj;
 
@@ -34,7 +37,10 @@ public static Selector from(Map<?, ?> map) {
     Object matchesObj = map.get("matches");
     if (matchesObj != null && !(matchesObj instanceof List)) {
       throw new StableConfigMappingException(
-          "'matches' must be a list, but got: " + matchesObj.getClass().getSimpleName());
+          "'matches' must be a list, but got: "
+              + matchesObj.getClass().getSimpleName()
+              + ", value: "
+              + StableConfigMappingException.safeToString(matchesObj));
     }
     List<String> rawMatches = (List<String>) matchesObj;
     List<String> matches =
@@ -46,7 +52,10 @@ public static Selector from(Map<?, ?> map) {
     }
     if (!(operatorObj instanceof String)) {
       throw new StableConfigMappingException(
-          "'operator' must be a string, but got: " + operatorObj.getClass().getSimpleName());
+          "'operator' must be a string, but got: "
+              + operatorObj.getClass().getSimpleName()
+              + ", value: "
+              + StableConfigMappingException.safeToString(operatorObj));
     }
     String operator = (String) operatorObj;
 

internal-api/src/main/java/datadog/trace/bootstrap/config/provider/stableconfig/StableConfig.java

@@ -54,7 +54,9 @@ private List<Rule> parseRules(Map<?, ?> map) {
           // Log or throw with a detailed message
           throw new StableConfigMappingException(
               "Rule must be a map, but got: "
-                  + (ruleObj == null ? "null" : ruleObj.getClass().getSimpleName()));
+                  + (ruleObj == null ? "null" : ruleObj.getClass().getSimpleName())
+                  + ", value: "
+                  + StableConfigMappingException.safeToString(ruleObj));
         }
       }
       return unmodifiableList(rules);

internal-api/src/main/java/datadog/trace/bootstrap/config/provider/stableconfig/StableConfigMappingException.java

@@ -8,4 +8,13 @@ public StableConfigMappingException(String message) {
   public StableConfigMappingException(String message, Throwable cause) {
     super(message, cause);
   }
+
+  public static String safeToString(Object value) {
+    if (value == null) return "null";
+    String str = value.toString();
+    if (str.length() > 100) {
+      return str.substring(0, 100) + "...(truncated)";
+    }
+    return str;
+  }
 }

internal-api/src/test/groovy/datadog/trace/bootstrap/config/provider/StableConfigSourceTest.groovy

@@ -135,52 +135,53 @@ class StableConfigSourceTest extends DDSpecification {
 
     where:
     yaml                                                                                           | expectedLogSubstring
-    // Missing 'origin' in selector
     '''apm_configuration_rules:
-         - selectors:
-             - key: "someKey"
-               matches: ["someValue"]
-               operator: equals
-           configuration:
-             DD_SERVICE: "test"
-    '''                                                                                             | "Missing 'origin' in selector"
-    // Missing 'configuration' in rule
+          - selectors:
+              - key: "someKey"
+                matches: ["someValue"]
+                operator: equals
+            configuration:
+              DD_SERVICE: "test"
+     '''                                                                                             | "Missing 'origin' in selector"
     '''apm_configuration_rules:
-         - selectors:
-             - origin: process_arguments
-               key: "-Dfoo"
-               matches: ["bar"]
-               operator: equals
-    '''                                                                                             | "Missing 'configuration' in rule"
-    // Missing 'selectors' in rule
+          - selectors:
+              - origin: process_arguments
+                key: "-Dfoo"
+                matches: ["bar"]
+                operator: equals
+     '''                                                                                             | "Missing 'configuration' in rule"
     '''apm_configuration_rules:
          - configuration:
              DD_SERVICE: "test"
     '''                                                                                             | "Missing 'selectors' in rule"
-    // Triggers ClassCastException (selectors should be a list, not a string)
     '''apm_configuration_rules:
-         - selectors: "not-a-list"
-           configuration:
-             DD_SERVICE: "test"
-    '''                                                                                             | "'selectors' must be a list, but got: String"
-    // configuration present but not a map
+          - selectors: "not-a-list"
+            configuration:
+              DD_SERVICE: "test"
+     '''                                                                                             | "'selectors' must be a list, but got: String"
+    '''apm_configuration_rules:
+          - selectors:
+              - "not-a-map"
+     '''                                                                                             | "Each selector must be a map, but got: String"
+    '''apm_configuration_rules:
+          - selectors:
+              - origin: process_arguments
+                key: "-Dfoo"
+                matches: ["bar"]
+                operator: equals
+            configuration: "not-a-map"
+     '''                                                                                             | "'configuration' must be a map, but got: String"
     '''apm_configuration_rules:
-         - selectors:
-             - origin: process_arguments
-               key: "-Dfoo"
-               matches: ["bar"]
-               operator: equals
-           configuration: "not-a-map"
-    '''                                                                                             | "'configuration' must be a map, but got: String"
-    // configuration present but not a map (integer)
+          - selectors:
+              - origin: process_arguments
+                key: "-Dfoo"
+                matches: ["bar"]
+                operator: equals
+            configuration: 12345
+     '''                                                                                             | "'configuration' must be a map, but got: Integer"
     '''apm_configuration_rules:
-         - selectors:
-             - origin: process_arguments
-               key: "-Dfoo"
-               matches: ["bar"]
-               operator: equals
-           configuration: 12345
-    '''                                                                                             | "'configuration' must be a map, but got: Integer"
+          - "not-a-map"
+     '''                                                                                             | "Rule must be a map, but got: String"
   }
 
   // Corrupt YAML string variable used for testing, defined outside the 'where' block for readability