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

/*
 * Copyright (C) 2014 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 com.android.annotations.NonNull;
import com.android.annotations.Nullable;
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.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.UCallExpression;

/** Checks for errors related to Date Formats */
public class DateFormatDetector extends Detector implements SourceCodeScanner {

    private static final Implementation IMPLEMENTATION =
            new Implementation(DateFormatDetector.class, Scope.JAVA_FILE_SCOPE);

    /** Constructing SimpleDateFormat without an explicit locale */
    public static final Issue DATE_FORMAT =
            Issue.create(
                            "SimpleDateFormat",
                            "Implied locale in date format",
                            "Almost all callers should use `getDateInstance()`, `getDateTimeInstance()`, or "
                                    + "`getTimeInstance()` to get a ready-made instance of SimpleDateFormat suitable "
                                    + "for the user's locale. The main reason you'd create an instance this class "
                                    + "directly is because you need to format/parse a specific machine-readable format, "
                                    + "in which case you almost certainly want to explicitly ask for US to ensure that "
                                    + "you get ASCII digits (rather than, say, Arabic digits).\n"
                                    + "\n"
                                    + "Therefore, you should either use the form of the SimpleDateFormat constructor "
                                    + "where you pass in an explicit locale, such as Locale.US, or use one of the "
                                    + "get instance methods, or suppress this error if really know what you are doing.",
                            Category.CORRECTNESS,
                            6,
                            Severity.WARNING,
                            IMPLEMENTATION)
                    .addMoreInfo(
                            "http://developer.android.com/reference/java/text/SimpleDateFormat.html");

    public static final String LOCALE_CLS = "java.util.Locale";
    public static final String SIMPLE_DATE_FORMAT_CLS = "java.text.SimpleDateFormat";

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

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

    @Nullable
    @Override
    public List<String> getApplicableConstructorTypes() {
        return Collections.singletonList(SIMPLE_DATE_FORMAT_CLS);
    }

    @Override
    public void visitConstructor(
            @NonNull JavaContext context,
            @NonNull UCallExpression node,
            @NonNull PsiMethod constructor) {
        if (!specifiesLocale(constructor)) {
            Location location = context.getLocation(node);
            String message =
                    "To get local formatting use `getDateInstance()`, `getDateTimeInstance()`, "
                            + "or `getTimeInstance()`, or use `new SimpleDateFormat(String template, "
                            + "Locale locale)` with for example `Locale.US` for ASCII dates.";
            context.report(DATE_FORMAT, node, location, message);
        }
    }

    private static boolean specifiesLocale(@NonNull PsiMethod method) {
        PsiParameterList parameterList = method.getParameterList();
        PsiParameter[] parameters = parameterList.getParameters();
        for (PsiParameter parameter : parameters) {
            PsiType type = parameter.getType();
            if (type.getCanonicalText().equals(LOCALE_CLS)) {
                return true;
            }
        }

        return false;
    }
}