From 2ce963284ef612ee0a8ad734e94f022ef9738a72 Mon Sep 17 00:00:00 2001
From: ghm <ghm@google.com>
Date: Wed, 23 Oct 2024 07:04:25 -0700
Subject: [PATCH] Strip the quotation marks from the source code when
 reconstructing the literal.

My comment was a lie. This does obviously matter, because it's important to work out if the \s is at the end of the entire string.

PiperOrigin-RevId: 688949631
---
 .../bugpatterns/MisleadingEscapedSpace.java   | 55 ++++++++++---------
 .../MisleadingEscapedSpaceTest.java           | 33 +++++++++++
 2 files changed, 63 insertions(+), 25 deletions(-)

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/MisleadingEscapedSpace.java b/core/src/main/java/com/google/errorprone/bugpatterns/MisleadingEscapedSpace.java
index 800d30f98ab..3290b2d40b2 100644
--- a/core/src/main/java/com/google/errorprone/bugpatterns/MisleadingEscapedSpace.java
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/MisleadingEscapedSpace.java
@@ -19,7 +19,6 @@
 import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
 import static com.google.errorprone.matchers.Description.NO_MATCH;
 import static com.google.errorprone.util.SourceVersion.supportsTextBlocks;
-import static java.util.stream.Collectors.joining;
 
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.VisitorState;
@@ -56,32 +55,38 @@ public Description matchLiteral(LiteralTree tree, VisitorState state) {
       // Tokenize the source to make sure we omit comments. Desugaring of "a" + "b" into a single
       // string literal happens really early in compilation, and we want to ensure we don't match
       // on any "\s" in comments.
-      // This is quite ugly in that we end up with a string that looks like "foo""bar", i.e.
-      // including the quotes, but that doesn't matter for this check.
       var tokens = ErrorProneTokens.getTokens(source, state.context);
-      var literal =
-          tokens.stream()
-              .filter(t -> t.kind().equals(TokenKind.STRINGLITERAL))
-              .map(t -> source.substring(t.pos(), t.endPos()))
-              .collect(joining());
-      boolean seenEscape = false;
-      for (int i = 0; i < literal.length(); ++i) {
-        switch (literal.charAt(i)) {
-          case '\n':
-            seenEscape = false;
-            break;
-          case '\\':
-            i++;
-            if (literal.charAt(i) == 's') {
-              seenEscape = true;
+      for (var token : tokens) {
+        if (!token.kind().equals(TokenKind.STRINGLITERAL)) {
+          continue;
+        }
+        var sourceWithQuotes = source.substring(token.pos(), token.endPos());
+        boolean isBlockLiteral = sourceWithQuotes.startsWith("\"\"\"");
+        int quoteSize = isBlockLiteral ? 3 : 1;
+        var literal = sourceWithQuotes.substring(quoteSize, sourceWithQuotes.length() - quoteSize);
+        boolean seenEscape = false;
+        for (int i = 0; i < literal.length(); ++i) {
+          switch (literal.charAt(i)) {
+            case '\n':
+              seenEscape = false;
+              break;
+            case '\\':
+              i++;
+              if (literal.charAt(i) == 's') {
+                seenEscape = true;
+                break;
+              }
+            // fall through
+            default:
+              if (seenEscape) {
+                return describeMatch(tree);
+              }
               break;
-            }
-          // fall through
-          default:
-            if (seenEscape) {
-              return describeMatch(tree);
-            }
-            break;
+          }
+        }
+        // Catch _trailing_ \s at the end of non-block literals.
+        if (seenEscape && !isBlockLiteral) {
+          return describeMatch(tree);
         }
       }
     }
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/MisleadingEscapedSpaceTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/MisleadingEscapedSpaceTest.java
index 348a4058640..8bfa78708b2 100644
--- a/core/src/test/java/com/google/errorprone/bugpatterns/MisleadingEscapedSpaceTest.java
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/MisleadingEscapedSpaceTest.java
@@ -140,4 +140,37 @@ class Test {
             }""")
         .doTest();
   }
+
+  @Test
+  public void atEndOfString_noFinding() {
+    assume().that(Runtime.version().feature()).isAtLeast(14);
+
+    testHelper
+        .addSourceLines(
+            "Test.class",
+            """
+            class Test {
+              private static final String FOO =
+                  \"""
+              foo
+              bar\\s\""";
+            }
+            """)
+        .doTest();
+  }
+
+  @Test
+  public void escapedSpaceAtEndOfString() {
+    assume().that(Runtime.version().feature()).isAtLeast(14);
+
+    testHelper
+        .addSourceLines(
+            "Test.class",
+            """
+            class Test {
+              // BUG: Diagnostic contains:
+              private static final String FOO = "foo\\s";
+            }""")
+        .doTest();
+  }
 }