feat: Generate enum with no keys for large properties files

Use EnumType#NO_KEYS in @L10nProperties to generate an enum with no keys.

This can be used to work with large properties files that generate the following compilation
error: "error: code too large" when the enum becomes too large with {@link #KEYS_ONLY} due
the number of keys.

Obviously strong typing does not apply anymore but other enum attribute can be used for
example to create an instance of L10nMessages with {@link L10nMessages#builder(Class)}

l10nmessages-proc/src/main/java/com/pinterest/l10nmessages/L10nPropertiesEnumGenerator.java

@@ -51,8 +51,9 @@ public static String toEnum(
 
     String enumValues =
         deduplicatedWithReporting.keySet().stream()
-            .map(key -> String.format("  %s(\"%s\")", toJavaIdentifier.convert(key), key))
-            .collect(Collectors.joining(",\n"));
+                .map(key -> String.format("  %s(\"%s\")", toJavaIdentifier.convert(key), key))
+                .collect(Collectors.joining(",\n"))
+            + ";";
 
     String packageString =
         nameParts.getDotPackageName().isEmpty()
@@ -67,32 +68,42 @@ public static String toEnum(
             + "\n"
             + "@Generated(\"%4$s\")\n"
             + "public enum %5$s {\n"
-            + "%6$s;\n"
+            + "%6$s\n"
             + "\n"
             + "  public static final String BASENAME = \"%7$s\";\n"
             + "  public static final String MESSAGE_FORMAT_ADAPTER_PROVIDERS = \"%8$s\";\n"
             + "\n"
-            + "  private String key;\n"
-            + "\n"
-            + "  %5$s(String key) {\n"
-            + "    this.key = key;\n"
-            + "  }\n"
-            + "\n"
-            + "  @Override\n"
-            + "  public String toString() {\n"
-            + "    return key;\n"
-            + "  }\n"
             + "%9$s"
+            + "%10$s"
             + "}\n",
         packageString, // 1
         enumType.WITH_ARGUMENT_BUILDERS.equals(enumType) ? IMPORT_STATEMENT_FOR_ARGUMENTS : "", // 2
         IMPORT_GENERATED_ANNOTATION, // 3
         generatedAnnotationValue, // 4
         nameParts.getEnumName(), // 5
-        enumValues, // 6
+        enumType.NO_KEYS.equals(enumType) ? "  ;" : enumValues, // 6
         nameParts.getBaseName(), // 7
         messageFormatAdapterProviders, // 8
-        enumType.WITH_ARGUMENT_BUILDERS.equals(enumType) ? formatContexts + "\n" : ""); // 9
+        enumType.NO_KEYS.equals(enumType) ? "" : generateConstructorBlock(nameParts.getEnumName()),
+        // 9
+        enumType.WITH_ARGUMENT_BUILDERS.equals(enumType) ? formatContexts + "\n" : "" // 10
+        );
+  }
+
+  private static String generateConstructorBlock(String enumName) {
+    return String.format(
+        ""
+            + "  private String key;\n"
+            + "\n"
+            + "  %1$s(String key) {\n"
+            + "    this.key = key;\n"
+            + "  }\n"
+            + "\n"
+            + "  @Override\n"
+            + "  public String toString() {\n"
+            + "    return key;\n"
+            + "  }\n",
+        enumName);
   }
 
   private static String generateFormatContextForEntry(

l10nmessages-proc/src/test/java/com/pinterest/l10nmessages/L10nPropertiesEnumGeneratorTest.java

@@ -133,4 +133,41 @@ void toEnum() {
                 + "}\n",
             enumString);
   }
+
+  @Test
+  void toEnumWithNoKeys() {
+    String baseName = "com.pinterest.l10nmessages.Messages";
+    NameParts nameParts = NameParts.fromBaseName(baseName);
+
+    LinkedHashMap<String, String> entries =
+        (LinkedHashMap<String, String>)
+            Maps.of(
+                "hello_username", "Hello {userName}, {count}",
+                "bye", "Bye");
+
+    String enumString =
+        L10nPropertiesEnumGenerator.toEnum(
+            entries,
+            nameParts,
+            ToJavaIdentifiers.ESCAPING_AND_UNDERSCORE,
+            MessageFormatAdapterProviders.JDK_NAMED_ARGS,
+            L10nPropertiesProcessor.class.getName(),
+            EnumType.NO_KEYS);
+
+    assertThat(enumString)
+        .isEqualTo(
+            "package com.pinterest.l10nmessages;\n"
+                + "\n"
+                + L10nPropertiesEnumGenerator.IMPORT_GENERATED_ANNOTATION
+                + "\n"
+                + "@Generated(\"com.pinterest.l10nmessages.L10nPropertiesProcessor\")\n"
+                + "public enum Messages {\n"
+                + "  ;\n"
+                + "\n"
+                + "  public static final String BASENAME = \"com.pinterest.l10nmessages.Messages\";\n"
+                + "  public static final String MESSAGE_FORMAT_ADAPTER_PROVIDERS = \"JDK_NAMED_ARGS\";\n"
+                + "\n"
+                + "}\n",
+            enumString);
+  }
 }

l10nmessages-proc/src/test/java/com/pinterest/l10nmessages/L10nPropertiesProcessorTest.java

@@ -53,6 +53,13 @@ public void validArgumentBuilder() {
     checkGenerationSuccessful(compilation);
   }
 
+  @Test
+  public void validNoKey() {
+    assumeTrue(shouldUseOldGeneratedAnnotation());
+    Compilation compilation = defaultCompile();
+    checkGenerationSuccessful(compilation);
+  }
+
   @Test
   public void validJava9() {
     assumeFalse(shouldUseOldGeneratedAnnotation());

l10nmessages-proc/src/test/resources/com/pinterest/l10nmessages/L10nPropertiesProcessorTest_IO/validNoKey/TestApp.java

@@ -0,0 +1,9 @@
+package com.pinterest.l10nmessages.L10nPropertiesProcessorTest_IO.valid;
+
+import com.pinterest.l10nmessages.EnumType;
+import com.pinterest.l10nmessages.L10nProperties;
+
+@L10nProperties(baseName = "com.pinterest.l10nmessages.L10nPropertiesProcessorTest_IO.validNoKey.TestMessages",
+ enumType = EnumType.NO_KEYS)
+public class TestApp {
+}

l10nmessages-proc/src/test/resources/com/pinterest/l10nmessages/L10nPropertiesProcessorTest_IO/validNoKey/TestMessages.java

@@ -0,0 +1,12 @@
+package com.pinterest.l10nmessages.L10nPropertiesProcessorTest_IO.validNoKey;
+
+import javax.annotation.Generated;
+
+@Generated("com.pinterest.l10nmessages.L10nPropertiesProcessor")
+public enum TestMessages {
+  ;
+
+  public static final String BASENAME = "com.pinterest.l10nmessages.L10nPropertiesProcessorTest_IO.validNoKey.TestMessages";
+  public static final String MESSAGE_FORMAT_ADAPTER_PROVIDERS = "AUTO";
+
+}

l10nmessages-proc/src/test/resources/com/pinterest/l10nmessages/L10nPropertiesProcessorTest_IO/validNoKey/TestMessages.properties

@@ -0,0 +1 @@
+hello_user=Hello {username}

l10nmessages/src/main/java/com/pinterest/l10nmessages/EnumType.java

@@ -9,6 +9,10 @@
  *
  * <p>{@link #WITH_ARGUMENT_BUILDERS} provide stronger typing but requires one class to be generated
  * by message with arguments. If this not acceptable, use {@link #KEYS_ONLY} (default value).
+ *
+ * <p>For large files with messages that are not referenced explicitly by key in code it is possible
+ * to generate the enum with no keys {@link #NO_KEYS}. The enum can still be used to create the
+ * L10nMessages instance but obviously there no type checking anymore.
  */
 public enum EnumType {
   /**
@@ -28,5 +32,17 @@ public enum EnumType {
    *
    * <p>Typically used with {@link com.pinterest.l10nmessages.L10nMessages#format(FormatContext)}
    */
-  WITH_ARGUMENT_BUILDERS
+  WITH_ARGUMENT_BUILDERS,
+  /**
+   * Generates an enum with no keys.
+   *
+   * <p>This can be used to work with large properties files that generate the following compilation
+   * error: "error: code too large" when the enum becomes too large with {@link #KEYS_ONLY}.
+   *
+   * <p>Obviously strong typing does not apply anymore but other enum attribute can be used for
+   * example to create an instance of L10nMessages with {@link L10nMessages#builder(Class)}
+   *
+   * <p>Typically used with {@link com.pinterest.l10nmessages.L10nMessages#format(Object)}
+   */
+  NO_KEYS,
 }