Remove method parameter protection analysis (#622)

This PR removes the method parameter protection feature from NullAway. This feature enables us to make `NullAway` to assume all method parameters at given index are `@Nullable` while processing the method bodies.  However, this feature is not used by the other tool ([Annotator](https://github.com/nimakarimipour/NullAwayAnnotator)) which had the first motivation toward implementing this feature.

In previous versions of [Annotator](https://github.com/nimakarimipour/NullAwayAnnotator), processing of method parameters was performed in a different manner compared to all other code locations and was using this specific feature. However, in every version upper that `1.3.0-LOCAL` this feature is not used anymore.

After this PR the following entity will be removed from the config `.xml` file:
```xml
<paramTest "active": boolean, "index": i> 
```

nullaway/src/main/java/com/uber/nullaway/fixserialization/FixSerializationConfig.java

@@ -59,18 +59,6 @@ public class FixSerializationConfig {
    */
   public final boolean fieldInitInfoEnabled;
 
-  /**
-   * If enabled, the formal parameter at index {@link FixSerializationConfig#paramTestIndex} in all
-   * methods will be treated as {@code @Nullable}
-   */
-  public final boolean methodParamProtectionTestEnabled;
-
-  /**
-   * Index of the formal parameter of all methods which will be considered {@code @Nullable}, if
-   * {@link FixSerializationConfig#methodParamProtectionTestEnabled} is enabled.
-   */
-  public final int paramTestIndex;
-
   /** The directory where all files generated/read by Fix Serialization package resides. */
   @Nullable public final String outputDirectory;
 
@@ -83,8 +71,6 @@ public FixSerializationConfig() {
     suggestEnabled = false;
     suggestEnclosing = false;
     fieldInitInfoEnabled = false;
-    methodParamProtectionTestEnabled = false;
-    paramTestIndex = Integer.MAX_VALUE;
     annotationConfig = new AnnotationConfig();
     outputDirectory = null;
     serializer = null;
@@ -94,15 +80,11 @@ public FixSerializationConfig(
       boolean suggestEnabled,
       boolean suggestEnclosing,
       boolean fieldInitInfoEnabled,
-      boolean methodParamProtectionTestEnabled,
-      int paramTestIndex,
       AnnotationConfig annotationConfig,
       String outputDirectory) {
     this.suggestEnabled = suggestEnabled;
     this.suggestEnclosing = suggestEnclosing;
     this.fieldInitInfoEnabled = fieldInitInfoEnabled;
-    this.methodParamProtectionTestEnabled = methodParamProtectionTestEnabled;
-    this.paramTestIndex = paramTestIndex;
     this.outputDirectory = outputDirectory;
     this.annotationConfig = annotationConfig;
     serializer = new Serializer(this);
@@ -142,12 +124,6 @@ public FixSerializationConfig(String configFilePath) {
         XMLUtil.getValueFromAttribute(
                 document, "/serialization/fieldInitInfo", "active", Boolean.class)
             .orElse(false);
-    methodParamProtectionTestEnabled =
-        XMLUtil.getValueFromAttribute(document, "/serialization/paramTest", "active", Boolean.class)
-            .orElse(false);
-    paramTestIndex =
-        XMLUtil.getValueFromAttribute(document, "/serialization/paramTest", "index", Integer.class)
-            .orElse(Integer.MAX_VALUE);
     String nullableAnnot =
         XMLUtil.getValueFromTag(document, "/serialization/annotation/nullable", String.class)
             .orElse("javax.annotation.Nullable");
@@ -169,8 +145,6 @@ public static class Builder {
     private boolean suggestEnabled;
     private boolean suggestEnclosing;
     private boolean fieldInitInfo;
-    private boolean methodParamProtectionTestEnabled;
-    private int paramIndex;
     private String nullable;
     private String nonnull;
     @Nullable private String outputDir;
@@ -205,12 +179,6 @@ public Builder setOutputDirectory(String outputDir) {
       return this;
     }
 
-    public Builder setParamProtectionTest(boolean value, int index) {
-      this.methodParamProtectionTestEnabled = value;
-      this.paramIndex = index;
-      return this;
-    }
-
     /**
      * Builds and writes the config with the state in builder at the given path as XML.
      *
@@ -229,8 +197,6 @@ public FixSerializationConfig build() {
           suggestEnabled,
           suggestEnclosing,
           fieldInitInfo,
-          methodParamProtectionTestEnabled,
-          paramIndex,
           new AnnotationConfig(nullable, nonnull),
           outputDir);
     }

nullaway/src/main/java/com/uber/nullaway/fixserialization/XMLUtil.java

@@ -121,13 +121,6 @@ public static void writeInXMLFormat(FixSerializationConfig config, String path)
       fieldInitInfoEnabled.setAttribute("active", String.valueOf(config.fieldInitInfoEnabled));
       rootElement.appendChild(fieldInitInfoEnabled);
 
-      // Method Parameter Protection Test
-      Element paramTestElement = doc.createElement("paramTest");
-      paramTestElement.setAttribute(
-          "active", String.valueOf(config.methodParamProtectionTestEnabled));
-      paramTestElement.setAttribute("index", String.valueOf(config.paramTestIndex));
-      rootElement.appendChild(paramTestElement);
-
       // Annotations
       Element annots = doc.createElement("annotation");
       Element nonnull = doc.createElement("nonnull");

nullaway/src/main/java/com/uber/nullaway/handlers/Handlers.java

@@ -68,10 +68,6 @@ public static Handler buildDefault(Config config) {
       handlerListBuilder.add(
           new FieldInitializationSerializationHandler(config.getSerializationConfig()));
     }
-    if (config.serializationIsActive()
-        && config.getSerializationConfig().methodParamProtectionTestEnabled) {
-      handlerListBuilder.add(new MethodParamNullableInjectorHandler(config));
-    }
     if (config.checkOptionalEmptiness()) {
       handlerListBuilder.add(new OptionalEmptinessHandler(config, methodNameUtil));
     }

nullaway/src/test/java/com/uber/nullaway/NullAwaySerializationTest.java

@@ -681,71 +681,6 @@ public void suggestCustomAnnotTest() {
         .doTest();
   }
 
-  @Test
-  public void examineMethodParamProtectionTest() {
-    Path tempRoot = Paths.get(temporaryFolder.getRoot().getAbsolutePath(), "custom_annot");
-    String output = tempRoot.toString();
-    SerializationTestHelper<FixDisplay> tester = new SerializationTestHelper<>(tempRoot);
-    try {
-      Files.createDirectories(tempRoot);
-      FixSerializationConfig.Builder builder =
-          new FixSerializationConfig.Builder()
-              .setSuggest(true, false)
-              .setParamProtectionTest(true, 0)
-              .setOutputDirectory(output);
-      Path config = tempRoot.resolve("serializer.xml");
-      Files.createFile(config);
-      configPath = config.toString();
-      builder.writeAsXML(configPath);
-    } catch (IOException ex) {
-      throw new UncheckedIOException(ex);
-    }
-    tester
-        .setArgs(
-            Arrays.asList(
-                "-d",
-                temporaryFolder.getRoot().getAbsolutePath(),
-                "-XepOpt:NullAway:AnnotatedPackages=com.uber",
-                "-XepOpt:NullAway:SerializeFixMetadata=true",
-                "-XepOpt:NullAway:FixSerializationConfigPath=" + configPath))
-        .addSourceLines(
-            "com/uber/Test.java",
-            "package com.uber;",
-            "public class Test {",
-            "   Object test(Object foo) {",
-            "       // BUG: Diagnostic contains: returning @Nullable",
-            "       return foo;",
-            "   }",
-            "   Object test1(Object foo, Object bar) {",
-            "       // BUG: Diagnostic contains: dereferenced expression foo is @Nullable",
-            "       Integer hash = foo.hashCode();",
-            "       return bar;",
-            "   }",
-            "   void test2(Object f) {",
-            "       // BUG: Diagnostic contains: passing @Nullable",
-            "       test1(f, new Object());",
-            "   }",
-            "}")
-        .setExpectedOutputs(
-            new FixDisplay(
-                "javax.annotation.Nullable",
-                "test(java.lang.Object)",
-                "null",
-                "METHOD",
-                "com.uber.Test",
-                "com/uber/Test.java"),
-            new FixDisplay(
-                "javax.annotation.Nullable",
-                "test1(java.lang.Object,java.lang.Object)",
-                "foo",
-                "PARAMETER",
-                "com.uber.Test",
-                "com/uber/Test.java"))
-        .setFactory(fixDisplayFactory)
-        .setOutputFileNameAndHeader(SUGGEST_FIX_FILE_NAME, SUGGEST_FIX_FILE_HEADER)
-        .doTest();
-  }
-
   @Test
   public void errorSerializationTest() {
     SerializationTestHelper<ErrorDisplay> tester = new SerializationTestHelper<>(root);