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Introduce
RedundantStringEscape check (#1138)
This check aims to simplify string constants by dropping redundant single quote escape sequences. The check is optimized for performance. While there, update existing checks such that they do not introduce violations of the type flagged by this new check.
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95
...prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/RedundantStringEscape.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,95 @@ | ||
| package tech.picnic.errorprone.bugpatterns; | ||
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| import static com.google.errorprone.BugPattern.LinkType.CUSTOM; | ||
| import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION; | ||
| import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION; | ||
| import static tech.picnic.errorprone.utils.Documentation.BUG_PATTERNS_BASE_URL; | ||
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| 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.LiteralTreeMatcher; | ||
| import com.google.errorprone.fixes.SuggestedFix; | ||
| import com.google.errorprone.matchers.Description; | ||
| import com.google.errorprone.util.ASTHelpers; | ||
| import com.sun.source.tree.LiteralTree; | ||
| import tech.picnic.errorprone.utils.SourceCode; | ||
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| /** A {@link BugChecker} that flags string constants with extraneous escaping. */ | ||
| // XXX: Also cover `\"` sequences inside text blocks. Note that this requires a more subtle | ||
| // approach, as double-quote characters will need to remain escaped if removing the backslash would | ||
| // create a new sequence of three or more double-quotes. (TBD whether we'd like to enforce a | ||
| // "preferred" approach to escaping, e.g. by always escaping the last of a triplet, such that the | ||
| // over-all number of escaped characters is minimized.) | ||
| // XXX: Also flag `'\"'` char literals. | ||
| @AutoService(BugChecker.class) | ||
| @BugPattern( | ||
| summary = "Inside string expressions single quotes do not need to be escaped", | ||
| link = BUG_PATTERNS_BASE_URL + "RedundantStringEscape", | ||
| linkType = CUSTOM, | ||
| severity = SUGGESTION, | ||
| tags = SIMPLIFICATION) | ||
| public final class RedundantStringEscape extends BugChecker implements LiteralTreeMatcher { | ||
| private static final long serialVersionUID = 1L; | ||
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| /** Instantiates a new {@link RedundantStringEscape} instance. */ | ||
| public RedundantStringEscape() {} | ||
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| @Override | ||
| public Description matchLiteral(LiteralTree tree, VisitorState state) { | ||
| String constant = ASTHelpers.constValue(tree, String.class); | ||
| if (constant == null || constant.indexOf('\'') < 0) { | ||
| /* Fast path: this isn't a string constant with a single quote. */ | ||
| return Description.NO_MATCH; | ||
| } | ||
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| String source = SourceCode.treeToString(tree, state); | ||
| if (!containsBannedEscapeSequence(source)) { | ||
| /* Semi-fast path: this expression doesn't contain an escaped single quote. */ | ||
| return Description.NO_MATCH; | ||
| } | ||
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| /* Slow path: suggest dropping the escape characters. */ | ||
| return describeMatch(tree, SuggestedFix.replace(tree, dropRedundantEscapeSequences(source))); | ||
| } | ||
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| /** | ||
| * Tells whether the given string constant source expression contains an escaped single quote. | ||
| * | ||
| * @implNote As the input is a literal Java string expression, it will start and end with a double | ||
| * quote; as such any found backslash will not be the string's final character. | ||
| */ | ||
| private static boolean containsBannedEscapeSequence(String source) { | ||
| for (int p = source.indexOf('\\'); p != -1; p = source.indexOf('\\', p + 2)) { | ||
| if (source.charAt(p + 1) == '\'') { | ||
| return true; | ||
| } | ||
| } | ||
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| return false; | ||
| } | ||
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| /** | ||
| * Simplifies the given string constant source expression by dropping the backslash preceding an | ||
| * escaped single quote. | ||
| * | ||
| * @implNote Note that this method does not delegate to {@link | ||
| * SourceCode#toStringConstantExpression}, as that operation may replace other Unicode | ||
| * characters with their associated escape sequence. | ||
| * @implNote As the input is a literal Java string expression, it will start and end with a double | ||
| * quote; as such any found backslash will not be the string's final character. | ||
| */ | ||
| private static String dropRedundantEscapeSequences(String source) { | ||
| StringBuilder result = new StringBuilder(); | ||
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| for (int p = 0; p < source.length(); p++) { | ||
| char c = source.charAt(p); | ||
| if (c != '\\' || source.charAt(p + 1) != '\'') { | ||
| result.append(c); | ||
| } | ||
| } | ||
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| return result.toString(); | ||
| } | ||
| } |
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90 changes: 90 additions & 0 deletions
90
...e-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RedundantStringEscapeTest.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,90 @@ | ||
| package tech.picnic.errorprone.bugpatterns; | ||
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| import com.google.errorprone.BugCheckerRefactoringTestHelper; | ||
| import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode; | ||
| import com.google.errorprone.CompilationTestHelper; | ||
| import org.junit.jupiter.api.Test; | ||
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| final class RedundantStringEscapeTest { | ||
| @Test | ||
| void identification() { | ||
| CompilationTestHelper.newInstance(RedundantStringEscape.class, getClass()) | ||
| .addSourceLines( | ||
| "A.java", | ||
| "import java.util.Arrays;", | ||
| "import java.util.List;", | ||
| "", | ||
| "class A {", | ||
| " List<String> m() {", | ||
| " return Arrays.asList(", | ||
| " \"foo\",", | ||
| " \"ß\",", | ||
| " \"'\",", | ||
| " \"\\\"\",", | ||
| " \"\\\\\",", | ||
| " \"\\\\'\",", | ||
| " \"'\\\\\",", | ||
| " // BUG: Diagnostic contains:", | ||
| " \"\\\\\\'\",", | ||
| " // BUG: Diagnostic contains:", | ||
| " \"\\'\\\\\",", | ||
| " // BUG: Diagnostic contains:", | ||
| " \"\\'\",", | ||
| " // BUG: Diagnostic contains:", | ||
| " \"'\\'\",", | ||
| " // BUG: Diagnostic contains:", | ||
| " \"\\''\",", | ||
| " // BUG: Diagnostic contains:", | ||
| " \"\\'\\'\",", | ||
| " (", | ||
| " // BUG: Diagnostic contains:", | ||
| " /* Leading comment. */ \"\\'\" /* Trailing comment. */),", | ||
| " // BUG: Diagnostic contains:", | ||
| " \"\\'foo\\\"bar\\'baz\\\"qux\\'\");", | ||
| " }", | ||
| "}") | ||
| .doTest(); | ||
| } | ||
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| @Test | ||
| void replacement() { | ||
| BugCheckerRefactoringTestHelper.newInstance(RedundantStringEscape.class, getClass()) | ||
| .addInputLines( | ||
| "A.java", | ||
| "import java.util.Arrays;", | ||
| "import java.util.List;", | ||
| "", | ||
| "class A {", | ||
| " List<String> m() {", | ||
| " return Arrays.asList(", | ||
| " \"\\'\",", | ||
| " \"'\\'\",", | ||
| " \"\\''\",", | ||
| " \"\\'\\'\",", | ||
| " \"\\'ß\\'\",", | ||
| " (", | ||
| " /* Leading comment. */ \"\\'\" /* Trailing comment. */),", | ||
| " \"\\'foo\\\"bar\\'baz\\\"qux\\'\");", | ||
| " }", | ||
| "}") | ||
| .addOutputLines( | ||
| "A.java", | ||
| "import java.util.Arrays;", | ||
| "import java.util.List;", | ||
| "", | ||
| "class A {", | ||
| " List<String> m() {", | ||
| " return Arrays.asList(", | ||
| " \"'\",", | ||
| " \"''\",", | ||
| " \"''\",", | ||
| " \"''\",", | ||
| " \"'ß'\",", | ||
| " (", | ||
| " /* Leading comment. */ \"'\" /* Trailing comment. */),", | ||
| " \"'foo\\\"bar'baz\\\"qux'\");", | ||
| " }", | ||
| "}") | ||
| .doTest(TestMode.TEXT_MATCH); | ||
| } | ||
| } |
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