Recommend efficient String operations. (a52266b3) · Commits · e / os / android_frameworks_base

errorprone/java/com/google/errorprone/bugpatterns/android/EfficientStringsChecker.java

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		/*
		* Copyright (C) 2020 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.google.errorprone.bugpatterns.android;

		import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
		import static com.google.errorprone.matchers.Matchers.allOf;
		import static com.google.errorprone.matchers.Matchers.contains;
		import static com.google.errorprone.matchers.Matchers.kindIs;
		import static com.google.errorprone.matchers.Matchers.methodInvocation;
		import static com.google.errorprone.matchers.Matchers.not;
		import static com.google.errorprone.matchers.Matchers.staticMethod;

		import com.google.auto.service.AutoService;
		import com.google.errorprone.BugPattern;
		import com.google.errorprone.VisitorState;
		import com.google.errorprone.bugpatterns.BugChecker;
		import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
		import com.google.errorprone.matchers.Description;
		import com.google.errorprone.matchers.Matcher;
		import com.google.errorprone.predicates.TypePredicate;
		import com.google.errorprone.util.ASTHelpers;
		import com.sun.source.tree.ExpressionTree;
		import com.sun.source.tree.LiteralTree;
		import com.sun.source.tree.MethodInvocationTree;
		import com.sun.source.tree.Tree.Kind;
		import com.sun.tools.javac.code.Symbol.VarSymbol;
		import com.sun.tools.javac.code.Type;

		import java.util.List;

		/**
		* Android offers several efficient alternatives to some upstream {@link String}
		* operations.
		*/
		@AutoService(BugChecker.class)
		@BugPattern(
		name = "AndroidFrameworkEfficientStrings",
		summary = "Verifies efficient Strings best-practices",
		severity = WARNING)
		public final class EfficientStringsChecker extends BugChecker
		implements MethodInvocationTreeMatcher {

		private static final Matcher<ExpressionTree> FORMAT_CALL = methodInvocation(
		staticMethod().onClass("java.lang.String").named("format"));
		private static final Matcher<ExpressionTree> PRECONDITIONS_CALL = methodInvocation(
		staticMethod().onClass(withSimpleName("Preconditions")).withAnyName());
		private static final Matcher<ExpressionTree> OBJECTS_CALL = methodInvocation(
		staticMethod().onClass("java.util.Objects").named("requireNonNull"));

		/**
		* Match an expression which combines both string literals any other dynamic
		* values, since these allocate a transparent StringBuilder.
		* <p>
		* This won't match a single isolated string literal, or a chain consisting
		* of only string literals, since those don't require dynamic construction.
		*/
		private static final Matcher<ExpressionTree> CONTAINS_DYNAMIC_STRING = allOf(
		contains(ExpressionTree.class, kindIs(Kind.STRING_LITERAL)),
		contains(ExpressionTree.class, not(kindIs(Kind.STRING_LITERAL))));

		@Override
		public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
		if (FORMAT_CALL.matches(tree, state)) {
		// Skip over possible locale to find format string
		final List<? extends ExpressionTree> args = tree.getArguments();
		final ExpressionTree formatArg;
		final List<VarSymbol> vars = ASTHelpers.getSymbol(tree).params();
		if (vars.get(0).type.toString().equals("java.util.Locale")) {
		formatArg = args.get(1);
		} else {
		formatArg = args.get(0);
		}

		// Determine if format string is "simple" enough to replace
		if (formatArg.getKind() == Kind.STRING_LITERAL) {
		final String format = String.valueOf(((LiteralTree) formatArg).getValue());
		if (isSimple(format)) {
		return buildDescription(formatArg)
		.setMessage("Simple format strings can be replaced with "
		+ "TextUtils.formatSimple() for a 6x performance improvement")
		.build();
		}
		}
		} else if (PRECONDITIONS_CALL.matches(tree, state)
		\|\| OBJECTS_CALL.matches(tree, state)) {
		final List<? extends ExpressionTree> args = tree.getArguments();
		for (int i = 1 ; i < args.size(); i++) {
		final ExpressionTree arg = args.get(i);
		if (CONTAINS_DYNAMIC_STRING.matches(arg, state)) {
		return buildDescription(arg)
		.setMessage("Building dynamic messages is discouraged, since they "
		+ "always allocate a transparent StringBuilder, even in "
		+ "the successful case")
		.build();
		}
		}
		}
		return Description.NO_MATCH;
		}

		static boolean isSimple(String format) {
		for (int i = 0; i < format.length(); i++) {
		char c = format.charAt(i);
		if (c == '%') {
		i++;
		c = format.charAt(i);
		switch (c) {
		case 'b':
		case 'c':
		case 'd':
		case 'f':
		case 's':
		case 'x':
		case '%':
		break;
		default:
		return false;
		}
		}
		}
		return true;
		}

		static TypePredicate withSimpleName(final String filter) {
		return new TypePredicate() {
		@Override
		public boolean apply(Type type, VisitorState state) {
		return type.tsym.getSimpleName().toString().equals(filter);
		}
		};
		}
		}

errorprone/tests/java/com/google/errorprone/bugpatterns/android/EfficientStringsCheckerTest.java

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+119 −0

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		/*
		* Copyright (C) 2020 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.google.errorprone.bugpatterns.android;

		import static junit.framework.Assert.assertFalse;
		import static junit.framework.Assert.assertTrue;

		import com.google.errorprone.CompilationTestHelper;

		import org.junit.Before;
		import org.junit.Test;
		import org.junit.runner.RunWith;
		import org.junit.runners.JUnit4;

		@RunWith(JUnit4.class)
		public class EfficientStringsCheckerTest {
		private CompilationTestHelper compilationHelper;

		@Before
		public void setUp() {
		compilationHelper = CompilationTestHelper.newInstance(
		EfficientStringsChecker.class, getClass());
		}

		@Test
		public void testSimple() {
		assertTrue(EfficientStringsChecker.isSimple(""));
		assertTrue(EfficientStringsChecker.isSimple("%s"));
		assertTrue(EfficientStringsChecker.isSimple("String %s%s and %%%% number %d%d together"));

		assertFalse(EfficientStringsChecker.isSimple("%04d"));
		assertFalse(EfficientStringsChecker.isSimple("%02x:%02x:%02x"));
		}

		@Test
		public void testFormat() {
		compilationHelper
		.addSourceLines("Example.java",
		"import java.util.Locale;",
		"public class Example {",
		" public void example(String str) {",
		" String.format(str, str);",
		" // BUG: Diagnostic contains:",
		" String.format(\"foo %s bar\", str);",
		" // BUG: Diagnostic contains:",
		" String.format(\"foo %d bar\", 42);",
		" String.format(\"foo %04d bar\", 42);",
		" }",
		" public void exampleLocale(String str) {",
		" String.format(Locale.US, str, str);",
		" // BUG: Diagnostic contains:",
		" String.format(Locale.US, \"foo %s bar\", str);",
		" // BUG: Diagnostic contains:",
		" String.format(Locale.US, \"foo %d bar\", 42);",
		" String.format(Locale.US, \"foo %04d bar\", 42);",
		" }",
		"}")
		.doTest();
		}

		@Test
		public void testPreconditions() {
		compilationHelper
		.addSourceFile("/android/util/Preconditions.java")
		.addSourceLines("Example.java",
		"import android.util.Preconditions;",
		"import java.util.Objects;",
		"public class Example {",
		" String str;",
		" public void checkState(boolean val) {",
		" Preconditions.checkState(val);",
		" Preconditions.checkState(val, str);",
		" Preconditions.checkState(val, \"foo\");",
		" Preconditions.checkState(val, \"foo\" + \"bar\");",
		" // BUG: Diagnostic contains:",
		" Preconditions.checkState(val, \"foo \" + val);",
		" }",
		" public void checkArgument(boolean val) {",
		" Preconditions.checkArgument(val);",
		" Preconditions.checkArgument(val, str);",
		" Preconditions.checkArgument(val, \"foo\");",
		" Preconditions.checkArgument(val, \"foo\" + \"bar\");",
		" // BUG: Diagnostic contains:",
		" Preconditions.checkArgument(val, \"foo \" + val);",
		" }",
		" public void checkNotNull(Object val) {",
		" Preconditions.checkNotNull(val);",
		" Preconditions.checkNotNull(val, str);",
		" Preconditions.checkNotNull(val, \"foo\");",
		" Preconditions.checkNotNull(val, \"foo\" + \"bar\");",
		" // BUG: Diagnostic contains:",
		" Preconditions.checkNotNull(val, \"foo \" + val);",
		" }",
		" public void requireNonNull(Object val) {",
		" Objects.requireNonNull(val);",
		" Objects.requireNonNull(val, str);",
		" Objects.requireNonNull(val, \"foo\");",
		" Objects.requireNonNull(val, \"foo\" + \"bar\");",
		" // BUG: Diagnostic contains:",
		" Objects.requireNonNull(val, \"foo \" + val);",
		" }",
		"}")
		.doTest();
		}
		}

errorprone/tests/res/android/util/Preconditions.java

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		/*
		* Copyright (C) 2020 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 android.util;

		public class Preconditions {
		public static void checkArgument(boolean expression) {
		throw new UnsupportedOperationException();
		}

		public static void checkArgument(boolean expression, Object errorMessage) {
		throw new UnsupportedOperationException();
		}

		public static <T> T checkNotNull(T reference) {
		throw new UnsupportedOperationException();
		}

		public static <T> T checkNotNull(T reference, Object errorMessage) {
		throw new UnsupportedOperationException();
		}

		public static void checkState(boolean expression) {
		throw new UnsupportedOperationException();
		}

		public static void checkState(boolean expression, String message) {
		throw new UnsupportedOperationException();
		}
		}