fix: treat backslash as escape character only inside quoted strings, matching Jinja2 behaviour (fixes #1304)

src/main/java/com/hubspot/jinjava/LegacyOverrides.java

@@ -19,6 +19,7 @@ public class LegacyOverrides {
     .withUseTrimmingForNotesAndExpressions(true)
     .withKeepNullableLoopValues(true)
     .withIteratorOnlyReverseFilter(true)
+    .withHandleBackslashInQuotesOnly(true)
     .build();
   public static final LegacyOverrides ALL = new LegacyOverrides.Builder()
     .withEvaluateMapKeys(true)
@@ -31,6 +32,7 @@ public class LegacyOverrides {
     .withUseTrimmingForNotesAndExpressions(true)
     .withKeepNullableLoopValues(true)
     .withIteratorOnlyReverseFilter(true)
+    .withHandleBackslashInQuotesOnly(true)
     .build();
   private final boolean evaluateMapKeys;
   private final boolean iterateOverMapKeys;
@@ -42,6 +44,7 @@ public class LegacyOverrides {
   private final boolean useTrimmingForNotesAndExpressions;
   private final boolean keepNullableLoopValues;
   private final boolean iteratorOnlyReverseFilter;
+  private final boolean handleBackslashInQuotesOnly;
 
   private LegacyOverrides(Builder builder) {
     evaluateMapKeys = builder.evaluateMapKeys;
@@ -54,6 +57,7 @@ private LegacyOverrides(Builder builder) {
     useTrimmingForNotesAndExpressions = builder.useTrimmingForNotesAndExpressions;
     keepNullableLoopValues = builder.keepNullableLoopValues;
     iteratorOnlyReverseFilter = builder.iteratorOnlyReverseFilter;
+    handleBackslashInQuotesOnly = builder.handleBackslashInQuotesOnly;
   }
 
   public static Builder newBuilder() {
@@ -100,6 +104,10 @@ public boolean isIteratorOnlyReverseFilter() {
     return iteratorOnlyReverseFilter;
   }
 
+  public boolean isHandleBackslashInQuotesOnly() {
+    return handleBackslashInQuotesOnly;
+  }
+
   public static class Builder {
 
     private boolean evaluateMapKeys = false;
@@ -112,6 +120,7 @@ public static class Builder {
     private boolean useTrimmingForNotesAndExpressions = false;
     private boolean keepNullableLoopValues = false;
     private boolean iteratorOnlyReverseFilter = false;
+    private boolean handleBackslashInQuotesOnly = false;
 
     private Builder() {}
 
@@ -134,7 +143,8 @@ public static Builder from(LegacyOverrides legacyOverrides) {
           legacyOverrides.useTrimmingForNotesAndExpressions
         )
         .withKeepNullableLoopValues(legacyOverrides.keepNullableLoopValues)
-        .withIteratorOnlyReverseFilter(legacyOverrides.iteratorOnlyReverseFilter);
+        .withIteratorOnlyReverseFilter(legacyOverrides.iteratorOnlyReverseFilter)
+        .withHandleBackslashInQuotesOnly(legacyOverrides.handleBackslashInQuotesOnly);
     }
 
     public Builder withEvaluateMapKeys(boolean evaluateMapKeys) {
@@ -192,5 +202,10 @@ public Builder withIteratorOnlyReverseFilter(boolean iteratorOnlyReverseFilter)
       this.iteratorOnlyReverseFilter = iteratorOnlyReverseFilter;
       return this;
     }
+
+    public Builder withHandleBackslashInQuotesOnly(boolean handleBackslashInQuotesOnly) {
+      this.handleBackslashInQuotesOnly = handleBackslashInQuotesOnly;
+      return this;
+    }
   }
 }

src/main/java/com/hubspot/jinjava/tree/TreeParser.java

@@ -32,13 +32,15 @@
 import com.hubspot.jinjava.lib.tag.FlexibleTag;
 import com.hubspot.jinjava.lib.tag.Tag;
 import com.hubspot.jinjava.tree.parse.ExpressionToken;
+import com.hubspot.jinjava.tree.parse.StringTokenScanner;
 import com.hubspot.jinjava.tree.parse.TagToken;
 import com.hubspot.jinjava.tree.parse.TextToken;
 import com.hubspot.jinjava.tree.parse.Token;
 import com.hubspot.jinjava.tree.parse.TokenScanner;
 import com.hubspot.jinjava.tree.parse.TokenScannerSymbols;
 import com.hubspot.jinjava.tree.parse.UnclosedToken;
 import com.hubspot.jinjava.tree.parse.WhitespaceControlParser;
+import java.util.Iterator;
 import org.apache.commons.lang3.StringUtils;
 
 public class TreeParser {
@@ -52,7 +54,7 @@ public class TreeParser {
 
   public TreeParser(JinjavaInterpreter interpreter, String input) {
     this.scanner =
-      Iterators.peekingIterator(new TokenScanner(input, interpreter.getConfig()));
+      Iterators.peekingIterator(createScanner(input, interpreter.getConfig()));
     this.interpreter = interpreter;
     this.symbols = interpreter.getConfig().getTokenScannerSymbols();
     this.whitespaceControlParser =
@@ -104,6 +106,13 @@ public Node buildTree() {
     return root;
   }
 
+  private static Iterator<Token> createScanner(String input, JinjavaConfig config) {
+    if (config.getTokenScannerSymbols().isStringBased()) {
+      return new StringTokenScanner(input, config);
+    }
+    return new TokenScanner(input, config);
+  }
+
   /**
    * @return null if EOF or error
    */

src/main/java/com/hubspot/jinjava/tree/parse/ExpressionToken.java

@@ -54,7 +54,14 @@ public int getType() {
 
   @Override
   protected void parse() {
-    this.expr = WhitespaceUtils.unwrap(image, "{{", "}}");
+    // Use the symbols-derived delimiter strings instead of the hardcoded "{{" / "}}"
+    // so that custom delimiters (e.g. "\VAR{" / "}") are stripped correctly.
+    this.expr =
+      WhitespaceUtils.unwrap(
+        image,
+        getSymbols().getExpressionStart(),
+        getSymbols().getExpressionEnd()
+      );
     this.expr = handleTrim(expr);
     this.expr = StringUtils.trimToEmpty(this.expr);
   }

src/main/java/com/hubspot/jinjava/tree/parse/NoteToken.java

@@ -48,8 +48,11 @@ public int getType() {
    */
   @Override
   protected void parse() {
-    if (image.length() > 4) { // {# #}
-      handleTrim(image.substring(2, image.length() - 2));
+    int startLen = getSymbols().getCommentStartLength();
+    int endLen = getSymbols().getCommentEndLength();
+
+    if (image.length() > startLen + endLen) {
+      handleTrim(image.substring(startLen, image.length() - endLen));
     }
     content = "";
   }