lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/LocaleDetector.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.FORMAT_METHOD;
import static com.android.tools.lint.client.api.JavaParser.TYPE_STRING;

import com.android.annotations.NonNull;
import com.android.annotations.Nullable;
import com.android.tools.lint.client.api.LintClient;
import com.android.tools.lint.detector.api.Category;
import com.android.tools.lint.detector.api.ConstantEvaluator;
import com.android.tools.lint.detector.api.Detector;
import com.android.tools.lint.detector.api.Detector.JavaPsiScanner;
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.intellij.psi.JavaElementVisitor;
import com.intellij.psi.PsiExpression;
import com.intellij.psi.PsiMethod;
import com.intellij.psi.PsiMethodCallExpression;
import com.intellij.psi.util.PsiTreeUtil;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * Checks for errors related to locale handling
 */
public class LocaleDetector extends Detector implements JavaPsiScanner {
    private static final Implementation IMPLEMENTATION = new Implementation(
            LocaleDetector.class,
            Scope.JAVA_FILE_SCOPE);

    /** Calling risky convenience methods */
    public static final Issue STRING_LOCALE = Issue.create(
            "DefaultLocale", //$NON-NLS-1$
            "Implied default locale in case conversion",

            "Calling `String#toLowerCase()` or `#toUpperCase()` *without specifying an " +
            "explicit locale* is a common source of bugs. The reason for that is that those " +
            "methods will use the current locale on the user's device, and even though the " +
            "code appears to work correctly when you are developing the app, it will fail " +
            "in some locales. For example, in the Turkish locale, the uppercase replacement " +
            "for `i` is *not* `I`.\n" +
            "\n" +
            "If you want the methods to just perform ASCII replacement, for example to convert " +
            "an enum name, call `String#toUpperCase(Locale.US)` instead. If you really want to " +
            "use the current locale, call `String#toUpperCase(Locale.getDefault())` instead.",

            Category.CORRECTNESS,
            6,
            Severity.WARNING,
            IMPLEMENTATION)
            .addMoreInfo(
            "http://developer.android.com/reference/java/util/Locale.html#default_locale"); //$NON-NLS-1$

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

    // ---- Implements JavaScanner ----

    @Override
    public List<String> getApplicableMethodNames() {
        if (LintClient.isStudio()) {
            // In the IDE, don't flag toUpperCase/toLowerCase; these
            // are already flagged by built-in IDE inspections, so we don't
            // want duplicate warnings.
            return Collections.singletonList(FORMAT_METHOD);
        } else {
            return Arrays.asList(
                    // Only when not running in the IDE
                    "toLowerCase", //$NON-NLS-1$
                    "toUpperCase", //$NON-NLS-1$
                    FORMAT_METHOD
            );
        }
    }

    @Override
    public void visitMethod(@NonNull JavaContext context, @Nullable JavaElementVisitor visitor,
            @NonNull PsiMethodCallExpression call, @NonNull PsiMethod method) {
        if (context.getEvaluator().isMemberInClass(method, TYPE_STRING)) {
            String name = method.getName();
            if (name.equals(FORMAT_METHOD)) {
                checkFormat(context, method, call);
            } else if (method.getParameterList().getParametersCount() == 0) {
                Location location = context.getNameLocation(call);
                String message = String.format(
                        "Implicitly using the default locale is a common source of bugs: " +
                                "Use `%1$s(Locale)` instead", name);
                context.report(STRING_LOCALE, call, location, message);
            }
        }
    }

    /** Returns true if the given node is a parameter to a Logging call */
    private static boolean isLoggingParameter(
            @NonNull JavaContext context,
            @NonNull PsiMethodCallExpression node) {
        PsiMethodCallExpression parentCall =
                PsiTreeUtil.getParentOfType(node, PsiMethodCallExpression.class, true);
        if (parentCall != null) {
            String name = parentCall.getMethodExpression().getReferenceName();
            if (name != null && name.length() == 1) { // "d", "i", "e" etc in Log
                PsiMethod method = parentCall.resolveMethod();
                return context.getEvaluator().isMemberInClass(method, LogDetector.LOG_CLS);
            }
        }

        return false;
    }

    private static void checkFormat(
            @NonNull JavaContext context,
            @NonNull PsiMethod method,
            @NonNull PsiMethodCallExpression call) {
        // Only check the non-locale version of String.format
        if (method.getParameterList().getParametersCount() == 0
                || !context.getEvaluator().parameterHasType(method, 0, TYPE_STRING)) {
            return;
        }

        PsiExpression[] expressions = call.getArgumentList().getExpressions();
        if (expressions.length == 0) {
            return;
        }

        // Find the formatting string
        PsiExpression first = expressions[0];
        Object value = ConstantEvaluator.evaluate(context, first);
        if (!(value instanceof String)) {
            return;
        }

        String format = (String) value;
        if (StringFormatDetector.isLocaleSpecific(format)) {
            if (isLoggingParameter(context, call)) {
                return;
            }
            Location location = context.getLocation(call);
            String message =
                    "Implicitly using the default locale is a common source of bugs: " +
                            "Use `String.format(Locale, ...)` instead";
            context.report(STRING_LOCALE, call, location, message);
        }
    }
}