Ensure that AutoBuilder works with property builders.

Previously it worked, but only if the builder interface also had a setter for the property. Otherwise you would get an exception because the template referenced the `$toBuilderMethods` variable, which was undefined.

RELNOTES=Fixed a bug with AutoBuilder and property builder methods.
PiperOrigin-RevId: 381330964

value/src/it/functional/src/test/java/com/google/auto/value/AutoBuilderTest.java

@@ -405,6 +405,30 @@ public void propertyBuilder() {
     }
   }
 
+  static <T> String concatList(ImmutableList<T> list) {
+    // We're avoiding streams for now so we compile this in Java 7 mode in CompileWithEclipseTest.
+    StringBuilder sb = new StringBuilder();
+    for (T element : list) {
+      sb.append(element);
+    }
+    return sb.toString();
+  }
+
+  @AutoBuilder(callMethod = "concatList")
+  interface ConcatListCaller<T> {
+    ImmutableList.Builder<T> listBuilder();
+
+    String call();
+  }
+
+  @Test
+  public void propertyBuilderWithoutSetter() {
+    ConcatListCaller<Integer> caller = new AutoBuilder_AutoBuilderTest_ConcatListCaller<>();
+    caller.listBuilder().add(1, 1, 2, 3, 5, 8);
+    String s = caller.call();
+    assertThat(s).isEqualTo("112358");
+  }
+
   static <K, V extends Number> Map<K, V> singletonMap(K key, V value) {
     return Collections.singletonMap(key, value);
   }

value/src/main/java/com/google/auto/value/processor/AutoBuilderProcessor.java

@@ -143,6 +143,7 @@ void processType(TypeElement autoBuilderType) {
     vars.build = build(executable);
     vars.types = typeUtils();
     vars.toBuilderConstructor = false;
+    vars.toBuilderMethods = ImmutableList.of();
     defineSharedVarsForType(autoBuilderType, ImmutableSet.of(), vars);
     String text = vars.toText();
     text = TypeEncoder.decode(text, processingEnv, vars.pkg, autoBuilderType.asType());

value/src/main/java/com/google/auto/value/processor/AutoValueOrBuilderTemplateVars.java

@@ -130,6 +130,13 @@ abstract class AutoValueOrBuilderTemplateVars extends AutoValueishTemplateVars {
    */
   Boolean toBuilderConstructor;
 
+  /**
+   * Any {@code toBuilder()} methods, that is methods that return the builder type. AutoBuilder does
+   * not currently support this, but it's included in these shared variables to simplify the
+   * template.
+   */
+  ImmutableList<SimpleMethod> toBuilderMethods;
+
   /**
    * Whether to include identifiers in strings in the generated code. If false, exception messages
    * will not mention properties by name, and {@code toString()} will include neither property names

value/src/main/java/com/google/auto/value/processor/AutoValueTemplateVars.java

@@ -15,7 +15,6 @@
  */
 package com.google.auto.value.processor;
 
-import com.google.common.collect.ImmutableList;
 import com.google.escapevelocity.Template;
 
 /**
@@ -42,9 +41,6 @@ class AutoValueTemplateVars extends AutoValueOrBuilderTemplateVars {
    */
   String modifiers;
 
-  /** Any {@code toBuilder()} methods, that is methods that return the builder type. */
-  ImmutableList<SimpleMethod> toBuilderMethods;
-
   private static final Template TEMPLATE = parsedTemplateForResource("autovalue.vm");
 
   @Override