Refactor for ErrorMessage class use (#284)

Makes the following changes:

- Move all the methods which are related to creating error message to an `ErrorBuilder` class.
- Use an `ErrorMessage` object as a parameter for `createErrorDescription`.
- `ErrorMessage` encapsulates both the text and type of the error.
- Other minor nits.

nullaway/src/main/java/com/uber/nullaway/ErrorBuilder.java

@@ -0,0 +1,314 @@
+/*
+ * Copyright (c) 2019 Uber Technologies, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.uber.nullaway;
+
+import static com.uber.nullaway.ErrorMessage.MessageTypes.FIELD_NO_INIT;
+import static com.uber.nullaway.ErrorMessage.MessageTypes.METHOD_NO_INIT;
+import static com.uber.nullaway.NullAway.INITIALIZATION_CHECK_NAME;
+import static com.uber.nullaway.NullAway.getTreesInstance;
+
+import com.google.common.base.Joiner;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.AnnotationTree;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.tree.MethodTree;
+import com.sun.source.tree.ModifiersTree;
+import com.sun.source.tree.Tree;
+import com.sun.source.tree.VariableTree;
+import com.sun.source.util.TreePath;
+import com.sun.tools.javac.code.Symbol;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.StreamSupport;
+import javax.annotation.Nullable;
+import javax.lang.model.element.Element;
+
+/** A class to construct error message to be displayed after the analysis finds error. */
+public class ErrorBuilder {
+
+  private final Config config;
+
+  /** Checker name that can be used to suppress the warnings. */
+  private final String suppressionName;
+
+  /** Additional identifiers for this check, to be checked for in @SuppressWarnings annotations. */
+  private final Set<String> allNames;
+
+  ErrorBuilder(Config config, String suppressionName, Set<String> allNames) {
+    this.config = config;
+    this.suppressionName = suppressionName;
+    this.allNames = allNames;
+  }
+
+  /**
+   * create an error description for a nullability warning
+   *
+   * @param errorMessage the error message object.
+   * @param path the TreePath to the error location. Used to compute a suggested fix at the
+   *     enclosing method for the error location
+   * @param descriptionBuilder the description builder for the error.
+   * @return the error description
+   */
+  Description createErrorDescription(
+      ErrorMessage errorMessage, TreePath path, Description.Builder descriptionBuilder) {
+    Tree enclosingSuppressTree = suppressibleNode(path);
+    return createErrorDescription(errorMessage, enclosingSuppressTree, descriptionBuilder);
+  }
+
+  /**
+   * create an error description for a nullability warning
+   *
+   * @param errorMessage the error message object.
+   * @param suggestTree the location at which a fix suggestion should be made
+   * @param descriptionBuilder the description builder for the error.
+   * @return the error description
+   */
+  public Description createErrorDescription(
+      ErrorMessage errorMessage,
+      @Nullable Tree suggestTree,
+      Description.Builder descriptionBuilder) {
+    Description.Builder builder = descriptionBuilder.setMessage(errorMessage.message);
+    if (config.suggestSuppressions() && suggestTree != null) {
+      switch (errorMessage.messageType) {
+        case DEREFERENCE_NULLABLE:
+        case RETURN_NULLABLE:
+        case PASS_NULLABLE:
+        case ASSIGN_FIELD_NULLABLE:
+          if (config.getCastToNonNullMethod() != null) {
+            builder = addCastToNonNullFix(suggestTree, builder);
+          } else {
+            builder = addSuppressWarningsFix(suggestTree, builder, suppressionName);
+          }
+          break;
+        case CAST_TO_NONNULL_ARG_NONNULL:
+          builder = removeCastToNonNullFix(suggestTree, builder);
+          break;
+        case WRONG_OVERRIDE_RETURN:
+          builder = addSuppressWarningsFix(suggestTree, builder, suppressionName);
+          break;
+        case WRONG_OVERRIDE_PARAM:
+          builder = addSuppressWarningsFix(suggestTree, builder, suppressionName);
+          break;
+        case METHOD_NO_INIT:
+        case FIELD_NO_INIT:
+          builder = addSuppressWarningsFix(suggestTree, builder, INITIALIZATION_CHECK_NAME);
+          break;
+        case ANNOTATION_VALUE_INVALID:
+          break;
+        default:
+          builder = addSuppressWarningsFix(suggestTree, builder, suppressionName);
+      }
+    }
+    // #letbuildersbuild
+    return builder.build();
+  }
+
+  /**
+   * create an error description for a generalized @Nullable value to @NonNull location assignment.
+   *
+   * <p>This includes: field assignments, method arguments and method returns
+   *
+   * @param errorMessage the error message object.
+   * @param suggestTreeIfCastToNonNull the location at which a fix suggestion should be made if a
+   *     castToNonNull method is available (usually the expression to cast)
+   * @param suggestTreePathIfSuppression the location at which a fix suggestion should be made if a
+   *     castToNonNull method is not available (usually the enclosing method, or any place
+   *     where @SuppressWarnings can be added).
+   * @param descriptionBuilder the description builder for the error.
+   * @return the error description.
+   */
+  Description createErrorDescriptionForNullAssignment(
+      ErrorMessage errorMessage,
+      @Nullable Tree suggestTreeIfCastToNonNull,
+      @Nullable TreePath suggestTreePathIfSuppression,
+      Description.Builder descriptionBuilder) {
+    final Tree enclosingSuppressTree = suppressibleNode(suggestTreePathIfSuppression);
+    if (config.getCastToNonNullMethod() != null) {
+      return createErrorDescription(errorMessage, suggestTreeIfCastToNonNull, descriptionBuilder);
+    } else {
+      return createErrorDescription(errorMessage, enclosingSuppressTree, descriptionBuilder);
+    }
+  }
+
+  Description.Builder addSuppressWarningsFix(
+      Tree suggestTree, Description.Builder builder, String suppressionName) {
+    SuppressWarnings extantSuppressWarnings =
+        ASTHelpers.getAnnotation(suggestTree, SuppressWarnings.class);
+    SuggestedFix fix;
+    if (extantSuppressWarnings == null) {
+      fix =
+          SuggestedFix.prefixWith(
+              suggestTree,
+              "@SuppressWarnings(\""
+                  + suppressionName
+                  + "\") "
+                  + config.getAutofixSuppressionComment());
+    } else {
+      // need to update the existing list of warnings
+      final List<String> suppressions = Lists.newArrayList(extantSuppressWarnings.value());
+      suppressions.add(suppressionName);
+      // find the existing annotation, so we can replace it
+      final ModifiersTree modifiers =
+          (suggestTree instanceof MethodTree)
+              ? ((MethodTree) suggestTree).getModifiers()
+              : ((VariableTree) suggestTree).getModifiers();
+      final List<? extends AnnotationTree> annotations = modifiers.getAnnotations();
+      // noinspection ConstantConditions
+      com.google.common.base.Optional<? extends AnnotationTree> suppressWarningsAnnot =
+          Iterables.tryFind(
+              annotations,
+              annot -> annot.getAnnotationType().toString().endsWith("SuppressWarnings"));
+      if (!suppressWarningsAnnot.isPresent()) {
+        throw new AssertionError("something went horribly wrong");
+      }
+      final String replacement =
+          "@SuppressWarnings({"
+              + Joiner.on(',').join(Iterables.transform(suppressions, s -> '"' + s + '"'))
+              + "}) "
+              + config.getAutofixSuppressionComment();
+      fix = SuggestedFix.replace(suppressWarningsAnnot.get(), replacement);
+    }
+    return builder.addFix(fix);
+  }
+
+  /**
+   * Adapted from {@link com.google.errorprone.fixes.SuggestedFixes}.
+   *
+   * <p>TODO: actually use {@link
+   * com.google.errorprone.fixes.SuggestedFixes#addSuppressWarnings(VisitorState, String)} instead
+   */
+  @Nullable
+  private Tree suppressibleNode(@Nullable TreePath path) {
+    if (path == null) {
+      return null;
+    }
+    return StreamSupport.stream(path.spliterator(), false)
+        .filter(
+            tree ->
+                tree instanceof MethodTree
+                    || (tree instanceof ClassTree
+                        && ((ClassTree) tree).getSimpleName().length() != 0)
+                    || tree instanceof VariableTree)
+        .findFirst()
+        .orElse(null);
+  }
+
+  private Description.Builder addCastToNonNullFix(Tree suggestTree, Description.Builder builder) {
+    final String fullMethodName = config.getCastToNonNullMethod();
+    assert fullMethodName != null;
+    // Add a call to castToNonNull around suggestTree:
+    final String[] parts = fullMethodName.split("\\.");
+    final String shortMethodName = parts[parts.length - 1];
+    final String replacement = shortMethodName + "(" + suggestTree.toString() + ")";
+    final SuggestedFix fix =
+        SuggestedFix.builder()
+            .replace(suggestTree, replacement)
+            .addStaticImport(fullMethodName) // ensure castToNonNull static import
+            .build();
+    return builder.addFix(fix);
+  }
+
+  private Description.Builder removeCastToNonNullFix(
+      Tree suggestTree, Description.Builder builder) {
+    assert suggestTree.getKind() == Tree.Kind.METHOD_INVOCATION;
+    final MethodInvocationTree invTree = (MethodInvocationTree) suggestTree;
+    final Symbol.MethodSymbol methodSymbol = ASTHelpers.getSymbol(invTree);
+    final String qualifiedName =
+        ASTHelpers.enclosingClass(methodSymbol) + "." + methodSymbol.getSimpleName().toString();
+    if (!qualifiedName.equals(config.getCastToNonNullMethod())) {
+      throw new RuntimeException("suggestTree should point to the castToNonNull invocation.");
+    }
+    // Remove the call to castToNonNull:
+    final SuggestedFix fix =
+        SuggestedFix.builder()
+            .replace(suggestTree, invTree.getArguments().get(0).toString())
+            .build();
+    return builder.addFix(fix);
+  }
+
+  void reportInitializerError(
+      Symbol.MethodSymbol methodSymbol,
+      String message,
+      VisitorState state,
+      Description.Builder descriptionBuilder) {
+    if (symbolHasSuppressInitializationWarningsAnnotation(methodSymbol)) {
+      return;
+    }
+    Tree methodTree = getTreesInstance(state).getTree(methodSymbol);
+    state.reportMatch(
+        createErrorDescription(
+            new ErrorMessage(METHOD_NO_INIT, message), methodTree, descriptionBuilder));
+  }
+
+  boolean symbolHasSuppressInitializationWarningsAnnotation(Symbol symbol) {
+    SuppressWarnings annotation = symbol.getAnnotation(SuppressWarnings.class);
+    if (annotation != null) {
+      for (String s : annotation.value()) {
+        // we need to check for standard suppression here also since we may report initialization
+        // errors outside the normal ErrorProne match* methods
+        if (s.equals(INITIALIZATION_CHECK_NAME) || allNames.stream().anyMatch(s::equals)) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  static String errMsgForInitializer(Set<Element> uninitFields) {
+    String message = "initializer method does not guarantee @NonNull ";
+    if (uninitFields.size() == 1) {
+      message += "field " + uninitFields.iterator().next().toString() + " is initialized";
+    } else {
+      message += "fields " + Joiner.on(", ").join(uninitFields) + " are initialized";
+    }
+    message += " along all control-flow paths (remember to check for exceptions or early returns).";
+    return message;
+  }
+
+  void reportInitErrorOnField(Symbol symbol, VisitorState state, Description.Builder builder) {
+    if (symbolHasSuppressInitializationWarningsAnnotation(symbol)) {
+      return;
+    }
+    Tree tree = getTreesInstance(state).getTree(symbol);
+    if (symbol.isStatic()) {
+      state.reportMatch(
+          createErrorDescription(
+              new ErrorMessage(
+                  FIELD_NO_INIT, "@NonNull static field " + symbol + " not initialized"),
+              tree,
+              builder));
+    } else {
+      state.reportMatch(
+          createErrorDescription(
+              new ErrorMessage(FIELD_NO_INIT, "@NonNull field " + symbol + " not initialized"),
+              tree,
+              builder));
+    }
+  }
+}

nullaway/src/main/java/com/uber/nullaway/ErrorMessage.java

@@ -1,11 +1,33 @@
+/*
+ * Copyright (c) 2019 Uber Technologies, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
 package com.uber.nullaway;
 
 /** Contains error message string to be displayed and the message type from {@link MessageTypes}. */
 public class ErrorMessage {
   MessageTypes messageType;
   String message;
 
-  ErrorMessage(MessageTypes messageType, String message) {
+  public ErrorMessage(MessageTypes messageType, String message) {
     this.messageType = messageType;
     this.message = message;
   }