lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/ViewConstructorDetector.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.tools.lint.checks;

import static com.android.SdkConstants.CLASS_ATTRIBUTE_SET;
import static com.android.SdkConstants.CLASS_CONTEXT;

import com.android.SdkConstants;
import com.android.annotations.NonNull;
import com.android.annotations.Nullable;
import com.android.tools.lint.client.api.JavaEvaluator;
import com.android.tools.lint.detector.api.Category;
import com.android.tools.lint.detector.api.Detector;
import com.android.tools.lint.detector.api.Implementation;
import com.android.tools.lint.detector.api.Issue;
import com.android.tools.lint.detector.api.JavaContext;
import com.android.tools.lint.detector.api.Location;
import com.android.tools.lint.detector.api.Scope;
import com.android.tools.lint.detector.api.Severity;
import com.android.tools.lint.detector.api.SourceCodeScanner;
import com.intellij.psi.PsiAnonymousClass;
import com.intellij.psi.PsiMethod;
import com.intellij.psi.PsiParameter;
import com.intellij.psi.PsiParameterList;
import com.intellij.psi.PsiType;
import java.util.Collections;
import java.util.List;
import org.jetbrains.uast.UClass;

/** Looks for custom views that do not define the view constructors needed by UI builders */
public class ViewConstructorDetector extends Detector implements SourceCodeScanner {
    /** The main issue discovered by this detector */
    public static final Issue ISSUE =
            Issue.create(
                            "ViewConstructor",
                            "Missing View constructors for XML inflation",
                            "Some layout tools (such as the Android layout editor) need to "
                                    + "find a constructor with one of the following signatures:\n"
                                    + "* `View(Context context)`\n"
                                    + "* `View(Context context, AttributeSet attrs)`\n"
                                    + "* `View(Context context, AttributeSet attrs, int defStyle)`\n"
                                    + "\n"
                                    + "If your custom view needs to perform initialization which does not apply when "
                                    + "used in a layout editor, you can surround the given code with a check to "
                                    + "see if `View#isInEditMode()` is false, since that method will return `false` "
                                    + "at runtime but true within a user interface editor.",
                            Category.USABILITY,
                            3,
                            Severity.WARNING,
                            new Implementation(
                                    ViewConstructorDetector.class, Scope.JAVA_FILE_SCOPE))
                    .setAndroidSpecific(true);

    /** Constructs a new {@link ViewConstructorDetector} check */
    public ViewConstructorDetector() {}

    // ---- implements SourceCodeScanner ----

    private static boolean isXmlConstructor(
            @NonNull JavaEvaluator evaluator, @NonNull PsiMethod method) {
        // Accept
        //   android.content.Context
        //   android.content.Context,android.util.AttributeSet
        //   android.content.Context,android.util.AttributeSet,int
        PsiParameterList parameterList = method.getParameterList();
        int argumentCount = parameterList.getParametersCount();
        if (argumentCount == 0 || argumentCount > 3) {
            return false;
        }
        PsiParameter[] parameters = parameterList.getParameters();
        if (!evaluator.typeMatches(parameters[0].getType(), CLASS_CONTEXT)) {
            return false;
        }
        if (argumentCount == 1) {
            return true;
        }
        if (!evaluator.typeMatches(parameters[1].getType(), CLASS_ATTRIBUTE_SET)) {
            return false;
        }
        //noinspection SimplifiableIfStatement
        if (argumentCount == 2) {
            return true;
        }
        return PsiType.INT.equals(parameters[2].getType());
    }

    @Nullable
    @Override
    public List<String> applicableSuperClasses() {
        return Collections.singletonList(SdkConstants.CLASS_VIEW);
    }

    @Override
    public void visitClass(@NonNull JavaContext context, @NonNull UClass declaration) {
        // Only applies to concrete classes
        JavaEvaluator evaluator = context.getEvaluator();
        if (evaluator.isAbstract(declaration)
                || evaluator.isPrivate(declaration)
                || declaration instanceof PsiAnonymousClass) {
            // Ignore abstract, private and anonymous classes
            return;
        }

        if (declaration.getContainingClass() != null && !evaluator.isStatic(declaration)) {
            // Ignore inner classes that aren't static: we can't create these
            // anyway since we'd need the outer instance
            return;
        }

        boolean found = false;
        for (PsiMethod constructor : declaration.getConstructors()) {
            if (isXmlConstructor(evaluator, constructor)) {
                found = true;
                break;
            }
        }

        if (!found) {
            String message =
                    String.format(
                            "Custom view `%1$s` is missing constructor used by tools: "
                                    + "`(Context)` or `(Context,AttributeSet)` "
                                    + "or `(Context,AttributeSet,int)`",
                            declaration.getName());
            Location location = context.getNameLocation(declaration);
            context.report(ISSUE, declaration, location, message);
        }
    }
}