If we dont match the regex for substitution return an error.

Additional tests.

gestalt-core/src/main/java/org/github/gestalt/config/entity/GestaltConfig.java

@@ -1,5 +1,7 @@
 package org.github.gestalt.config.entity;
 
+import org.github.gestalt.config.post.process.transform.TransformerPostProcessor;
+
 import java.time.format.DateTimeFormatter;
 
 /**
@@ -37,8 +39,7 @@ public class GestaltConfig {
 
     // the regex used to parse string substitutions.
     // Must have a named capture group transform, key, and default, where the key is required and the transform and default are optional.
-    private String substitutionRegex =
-        "((?<transform>\\w+):)?(?<key>[\\w ,_.+;\"'`~!@#$%^&*()\\[\\]<>]+)(:=(?<default>[\\w ,_.+;:\"'`~!@#$%^&*()\\[\\]<>]+))?";
+    private String substitutionRegex = TransformerPostProcessor.defaultSubstitutionRegex;
 
     /**
      * Treat all warnings as errors.

gestalt-core/src/main/java/org/github/gestalt/config/entity/ValidationError.java

@@ -1115,6 +1115,25 @@ public String description() {
         }
     }
 
+    /**
+     * Transform doesnt match the regex
+     */
+    public static class TransformDoesntMatchRegex extends ValidationError {
+        private final String path;
+        private final String value;
+
+        public TransformDoesntMatchRegex(String path, String value) {
+            super(ValidationLevel.ERROR);
+            this.path = path;
+            this.value = value;
+        }
+
+        @Override
+        public String description() {
+            return "Transform doesnt match the expected format with value " + value + " on path " + path;
+        }
+    }
+
     /**
      * Not a valid SubstitutionNode
      */

gestalt-core/src/main/java/org/github/gestalt/config/post/process/transform/TransformerPostProcessor.java

@@ -33,8 +33,8 @@
  */
 public class TransformerPostProcessor implements PostProcessor {
 
-    private static final String regexPattern =
-        "((?<transform>\\w+):)?(?<key>[\\w ,_.+;\"'`~!@#$%^&*()\\[\\]<>]+)(:=(?<default>[\\w ,_.+;:\"'`~!@#$%^&*()\\[\\]<>]+))?";
+    public static final String defaultSubstitutionRegex =
+        "^((?<transform>\\w+):)?(?<key>[\\w ,_.+;\"'`~!@#$%^&*()\\[\\]<>]+)(:=(?<default>[\\w ,_.+;:\"'`~!@#$%^&*()\\[\\]<>]+))?$";
     private Pattern pattern;
 
     private final Map<String, Transformer> transformers;
@@ -56,7 +56,7 @@ public TransformerPostProcessor() {
         });
 
         this.orderedDefaultTransformers = buildOrderedConfigPriorities(transformersList, false);
-        this.pattern = Pattern.compile(regexPattern);
+        this.pattern = Pattern.compile(defaultSubstitutionRegex);
     }
 
     /**
@@ -74,7 +74,7 @@ public TransformerPostProcessor(List<Transformer> transformers) {
         }
 
         this.substitutionTreeBuilder = new SubstitutionTreeBuilder("${", "}");
-        this.pattern = Pattern.compile(regexPattern);
+        this.pattern = Pattern.compile(defaultSubstitutionRegex);
     }
 
     @Override
@@ -85,7 +85,7 @@ public void applyConfig(PostProcessorConfig config) {
             config.getConfig().getSubstitutionClosingToken());
 
         this.maxRecursionDepth = config.getConfig().getMaxSubstitutionNestedDepth();
-        this.pattern = Pattern.compile(regexPattern);
+        this.pattern = Pattern.compile(defaultSubstitutionRegex);
     }
 
     @Override
@@ -207,7 +207,7 @@ private ValidateOf<String> transformString(String path, String input) {
         if (foundMatch) {
             return ValidateOf.valid(newLeafValue.toString());
         } else {
-            return ValidateOf.valid(input);
+            return ValidateOf.inValid(new ValidationError.TransformDoesntMatchRegex(path, input));
         }
     }
 }

gestalt-core/src/test/java/org/github/gestalt/config/post/process/transform/TransformerPostProcessorTest.java

@@ -97,6 +97,45 @@ void processTextWithMultipleDefaults() {
         Assertions.assertEquals("hello world it is sunny today", validateNode.results().getValue().get());
     }
 
+    @Test
+    void processTextWithMultipleDefaultsButHasValues() {
+
+        Map<String, String> customMap = new HashMap<>();
+        customMap.put("place", "world");
+        customMap.put("weather", "sunny");
+        CustomMapTransformer transformer = new CustomMapTransformer(customMap);
+
+        TransformerPostProcessor transformerPostProcessor = new TransformerPostProcessor(Collections.singletonList(transformer));
+        LeafNode node = new LeafNode("hello ${map:place:=earth} it is ${weather:=overcast} today");
+        ValidateOf<ConfigNode> validateNode = transformerPostProcessor.process("location", node);
+
+        Assertions.assertFalse(validateNode.hasErrors());
+        Assertions.assertTrue(validateNode.hasResults());
+        Assertions.assertTrue(validateNode.results().getValue().isPresent());
+        Assertions.assertEquals("hello world it is sunny today", validateNode.results().getValue().get());
+    }
+
+    @Test
+    void processInvalidFormat() {
+        // not sure about this test, this isnt "intended" behaviour. It just happens to happen.
+
+        Map<String, String> customMap = new HashMap<>();
+        customMap.put("place", "world");
+        customMap.put("weather", "sunny");
+        CustomMapTransformer transformer = new CustomMapTransformer(customMap);
+
+        TransformerPostProcessor transformerPostProcessor = new TransformerPostProcessor(Collections.singletonList(transformer));
+        LeafNode node = new LeafNode("${map:place:world}");
+        ValidateOf<ConfigNode> validateNode = transformerPostProcessor.process("location", node);
+
+        Assertions.assertTrue(validateNode.hasErrors());
+        Assertions.assertEquals(1, validateNode.getErrors().size());
+        Assertions.assertEquals("Transform doesnt match the expected format with value map:place:world on path location",
+            validateNode.getErrors().get(0).description());
+        Assertions.assertEquals(ValidationLevel.ERROR, validateNode.getErrors().get(0).level());
+
+    }
+
     @Test
     void processNoValue() {
         Map<String, String> customMap = new HashMap<>();

gestalt-core/src/test/resources/defaultPPEnv.properties

@@ -5,8 +5,8 @@ db.hosts[1].url=jdbc:postgresql://localhost:5432/mydb2
 db.hosts[2].user=credmond
 db.hosts[2].url=jdbc:postgresql://localhost:5432/mydb3
 db.ConnectionTimeout=6000
-db.idleTimeout=${envVar:DB_IDLETIMEOUT}
-db.maxLifetime=60000.0
+db.idleTimeout=${envVar:DB_IDLETIMEOUT:=900}
+db.maxLifetime=${envVar:NO_RESULTS_FOUND:=60000.0}
 http.Pool.maxTotal=100
 http.Pool.maxPerRoute=10
 http.Pool.validateAfterInactivity=6000

gestalt-examples/gestalt-sample/src/test/resources/defaultPPEnv.properties

@@ -5,8 +5,8 @@ db.hosts[1].url=jdbc:postgresql://localhost:5432/mydb2
 db.hosts[2].user=credmond
 db.hosts[2].url=jdbc:postgresql://localhost:5432/mydb3
 db.ConnectionTimeout=6000
-db.idleTimeout=${envVar:DB_IDLETIMEOUT}
-db.maxLifetime=60000.0
+db.idleTimeout=${envVar:DB_IDLETIMEOUT:=900}
+db.maxLifetime=${envVar:NO_RESULTS_FOUND:=60000.0}
 http.Pool.maxTotal=100
 http.Pool.maxPerRoute=10
 http.Pool.validateAfterInactivity=6000

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 java = "11"
 javaLatest = "19"
-kotlin = "1.8.20"
+kotlin = "1.8.21"
 kotlinDokka = "1.8.10"
 kodeinDI = "7.20.1"
 koinDI= "3.4.0"
@@ -23,7 +23,7 @@ junit5 = "5.9.2"
 assertJ = "3.24.2"
 mockito = "5.2.0"
 mockk = "1.13.5"
-koTestAssertions = "5.5.5"
+koTestAssertions = "5.6.1"
 awsMock = "2.11.0"
 
 errorprone = "2.18.0"