From fe18bed7c3eafdf4c5f8de001859d3c306c83a6e Mon Sep 17 00:00:00 2001
From: Bas Leijdekkers <basleijdekkers@gmail.com>
Date: Mon, 23 May 2016 16:18:20 +0200
Subject: [PATCH] regex: disallow literal backspace [\b] inside java

---
 .../src/org/intellij/lang/regexp/RegExpLanguageHost.java     | 4 ++++
 .../src/org/intellij/lang/regexp/RegExpLanguageHosts.java    | 5 +++++
 .../org/intellij/lang/regexp/validation/RegExpAnnotator.java | 2 +-
 RegExpSupport/testData/RETest.xml                            | 4 ++++
 java/java-impl/src/com/intellij/psi/impl/JavaRegExpHost.java | 5 +++++
 5 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/RegExpSupport/src/org/intellij/lang/regexp/RegExpLanguageHost.java b/RegExpSupport/src/org/intellij/lang/regexp/RegExpLanguageHost.java
index e00c1af129fe..1155e09ce160 100644
--- a/RegExpSupport/src/org/intellij/lang/regexp/RegExpLanguageHost.java
+++ b/RegExpSupport/src/org/intellij/lang/regexp/RegExpLanguageHost.java
@@ -38,6 +38,10 @@ public interface RegExpLanguageHost {
     return true;
   }
 
+  default boolean supportsLiteralBackspace(RegExpChar aChar) {
+    return true;
+  }
+
   boolean isValidCategory(@NotNull String category);
   @NotNull
   String[][] getAllKnownProperties();
diff --git a/RegExpSupport/src/org/intellij/lang/regexp/RegExpLanguageHosts.java b/RegExpSupport/src/org/intellij/lang/regexp/RegExpLanguageHosts.java
index 02b028d3d62f..71ac84ef0138 100644
--- a/RegExpSupport/src/org/intellij/lang/regexp/RegExpLanguageHosts.java
+++ b/RegExpSupport/src/org/intellij/lang/regexp/RegExpLanguageHosts.java
@@ -91,6 +91,11 @@ public final class RegExpLanguageHosts extends ClassExtension<RegExpLanguageHost
     }
   }
 
+  public boolean supportsLiteralBackspace(@Nullable RegExpChar regExpChar) {
+    final RegExpLanguageHost host = findRegExpHost(regExpChar);
+    return host != null && host.supportsLiteralBackspace(regExpChar);
+  }
+
   public boolean supportsNamedGroupSyntax(@Nullable final RegExpGroup group) {
     final RegExpLanguageHost host = findRegExpHost(group);
     return host != null && host.supportsNamedGroupSyntax(group);
diff --git a/RegExpSupport/src/org/intellij/lang/regexp/validation/RegExpAnnotator.java b/RegExpSupport/src/org/intellij/lang/regexp/validation/RegExpAnnotator.java
index 670bd1d0a051..d22ffc3ab107 100644
--- a/RegExpSupport/src/org/intellij/lang/regexp/validation/RegExpAnnotator.java
+++ b/RegExpSupport/src/org/intellij/lang/regexp/validation/RegExpAnnotator.java
@@ -133,7 +133,7 @@ public final class RegExpAnnotator extends RegExpElementVisitor implements Annot
   @Override
   public void visitRegExpChar(final RegExpChar ch) {
     final Character value = ch.getValue();
-    if (value == null) {
+    if (value == null || (value == '\b' && !myLanguageHosts.supportsLiteralBackspace(ch))) {
       switch (ch.getType()) {
         case CHAR:
           myHolder.createErrorAnnotation(ch, "Illegal/unsupported escape sequence");
diff --git a/RegExpSupport/testData/RETest.xml b/RegExpSupport/testData/RETest.xml
index 87b1ea104fa7..ee4fa31b8324 100644
--- a/RegExpSupport/testData/RETest.xml
+++ b/RegExpSupport/testData/RETest.xml
@@ -434,6 +434,10 @@
       <pattern><![CDATA[<weak_warning descr="Redundant character escape">\-</weak_warning>[<weak_warning descr="Redundant character escape">\*</weak_warning>\-\[\]\\<weak_warning descr="Redundant character escape">\+]</weak_warning>]]></pattern>
       <expected>OK</expected>
     </test>
+    <test host="com.intellij.psi.impl.JavaRegExpHost">
+      <pattern>[\b]</pattern>
+      <expected>ERR</expected>
+    </test>
   </charclasses>
 
   <groups>
diff --git a/java/java-impl/src/com/intellij/psi/impl/JavaRegExpHost.java b/java/java-impl/src/com/intellij/psi/impl/JavaRegExpHost.java
index e81feb553bbf..8f2e3a626943 100644
--- a/java/java-impl/src/com/intellij/psi/impl/JavaRegExpHost.java
+++ b/java/java-impl/src/com/intellij/psi/impl/JavaRegExpHost.java
@@ -101,6 +101,11 @@ public class JavaRegExpHost implements RegExpLanguageHost {
     }
   }
 
+  @Override
+  public boolean supportsLiteralBackspace(RegExpChar aChar) {
+    return false;
+  }
+
   private static boolean hasAtLeastJdkVersion(PsiElement element, JavaSdkVersion version) {
     final JavaSdkVersion version1 = getJavaVersion(element);
     return version1 != null && version1.isAtLeast(version);