Use one pattern violation wording in every target

CHANGELOG.md

@@ -27,6 +27,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- JSON Schema `pattern` violation reasons are now identical in every target:
+  `must match pattern "^[a-z]+$", got "AB1"`, with the authored pattern (not
+  Java's and Python's `$`→`\z` / `\Z` end-anchor rewrite) and the offending
+  value each quoted as a JSON string. Java previously printed both bare and Go
+  quoted with `%q`. A `propertyNames` pattern failure reads
+  `invalid property name "Bad": must match pattern "^[a-z]+$"` everywhere
+  (Java dropped the prefix and TypeScript appended `, got …`), and every
+  `invalid property name` prefix now JSON-quotes the key. Generated Java
+  `Violation` gains a public `quote(String)` helper.
 - Operation-free WIT interfaces now honor `@nexus.namespace`, and .NET names
   their namespace after the interface (`Nexgen.<InterfaceName>`) instead of
   falling back to `Nexgen.Generated`.

advanced/samples/java/src/main/java/json_schema/api/chat/Violation.java

@@ -28,6 +28,34 @@ public static String memberPath(String key) {
         return "[\"" + key.replace("\\", "\\\\").replace("\"", "\\\"") + "\"]";
     }
 
+    /** Quotes {@code value} as a JSON string literal for a violation reason. */
+    public static String quote(String value) {
+        StringBuilder out = new StringBuilder(value.length() + 2).append('"');
+        for (int i = 0; i < value.length(); i++) {
+            char c = value.charAt(i);
+            if (c == '"') {
+                out.append("\\\"");
+            } else if (c == '\\') {
+                out.append("\\\\");
+            } else if (c == '\b') {
+                out.append("\\b");
+            } else if (c == '\f') {
+                out.append("\\f");
+            } else if (c == '\n') {
+                out.append("\\n");
+            } else if (c == '\r') {
+                out.append("\\r");
+            } else if (c == '\t') {
+                out.append("\\t");
+            } else if (c < 0x20) {
+                out.append(String.format("\\u%04x", (int) c));
+            } else {
+                out.append(c);
+            }
+        }
+        return out.append('"').toString();
+    }
+
     public Violation withPathPrefix(String prefix) {
         if (path == null || path.isEmpty()) {
             return new Violation(prefix, reason);

advanced/samples/java/src/main/java/json_schema/api/kb/Violation.java

@@ -28,6 +28,34 @@ public static String memberPath(String key) {
         return "[\"" + key.replace("\\", "\\\\").replace("\"", "\\\"") + "\"]";
     }
 
+    /** Quotes {@code value} as a JSON string literal for a violation reason. */
+    public static String quote(String value) {
+        StringBuilder out = new StringBuilder(value.length() + 2).append('"');
+        for (int i = 0; i < value.length(); i++) {
+            char c = value.charAt(i);
+            if (c == '"') {
+                out.append("\\\"");
+            } else if (c == '\\') {
+                out.append("\\\\");
+            } else if (c == '\b') {
+                out.append("\\b");
+            } else if (c == '\f') {
+                out.append("\\f");
+            } else if (c == '\n') {
+                out.append("\\n");
+            } else if (c == '\r') {
+                out.append("\\r");
+            } else if (c == '\t') {
+                out.append("\\t");
+            } else if (c < 0x20) {
+                out.append(String.format("\\u%04x", (int) c));
+            } else {
+                out.append(c);
+            }
+        }
+        return out.append('"').toString();
+    }
+
     public Violation withPathPrefix(String prefix) {
         if (path == null || path.isEmpty()) {
             return new Violation(prefix, reason);

advanced/samples/java/src/main/java/json_schema/api/showcase/Attributes.java

@@ -78,7 +78,7 @@ public void serialize(Attributes value, JsonGenerator gen, SerializerProvider se
                 for (String pnKey : value.additionalProperties.keySet()) {
                     int pnLength = pnKey.codePointCount(0, pnKey.length());
                     if (pnLength > 8) {
-                        violations.add(new Violation(Violation.memberPath(pnKey), "invalid property name \"" + pnKey + "\": must have length <= 8, got " + pnLength));
+                        violations.add(new Violation(Violation.memberPath(pnKey), "invalid property name " + Violation.quote(pnKey) + ": must have length <= 8, got " + pnLength));
                     }
                 }
                 for (Map.Entry<String, String> entry : value.additionalProperties.entrySet()) {
@@ -138,7 +138,7 @@ public Attributes deserialize(JsonParser parser, DeserializationContext context)
                 String pnKey = propertyNameKeys.next();
                 int pnLength = pnKey.codePointCount(0, pnKey.length());
                 if (pnLength > 8) {
-                    violations.add(new Violation(Violation.memberPath(pnKey), "invalid property name \"" + pnKey + "\": must have length <= 8, got " + pnLength));
+                    violations.add(new Violation(Violation.memberPath(pnKey), "invalid property name " + Violation.quote(pnKey) + ": must have length <= 8, got " + pnLength));
                 }
             }
             if (!violations.isEmpty()) {