Logic \uXXXX escape support

core/src/mindustry/logic/LAssembler.java

@@ -81,7 +81,7 @@ public class LAssembler{
         }
     }
 
-    /** Decodes \n, \" and \\ escape sequences in a string literal's contents (quotes already stripped). */
+    /** Decodes \n, \", \\ and uXXXX escape sequences in a string literal's contents (quotes already stripped). */
     static String unescape(String s){
         if(s.indexOf('\\') == -1) return s;
 
@@ -98,6 +98,10 @@ public class LAssembler{
                     out.append(next);
                     i ++;
                     continue;
+                }else if(next == 'u' && i + 5 < s.length()){
+                    out.append((char)Integer.parseInt(s.substring(i + 2, i + 6), 16));
+                    i += 5;
+                    continue;
                 }
             }
             out.append(c);

core/src/mindustry/logic/LParser.java

@@ -56,6 +56,17 @@ public class LParser{
                 continue;
             }
 
+            //uXXXX: validate 4 hex digits
+            if(c == '\\' && pos + 1 < chars.length && chars[pos + 1] == 'u'){
+                if(pos + 5 >= chars.length) error("Invalid \\u escape; expected 4 hex digits.");
+                for(int j = pos + 2; j <= pos + 5; j++){
+                    if(Character.digit(chars[j], 16) == -1) error("Invalid \\u escape; expected 4 hex digits.");
+                }
+                utflen += 3; //decoded char may take up to 3 bytes in modified UTF-8
+                pos += 5; //consume u and the 4 hex digits
+                continue;
+            }
+
             if(c == '\n'){
                 error("Missing closing quote \" before end of line.");
             }else if(c == '"'){

core/src/mindustry/logic/LStatement.java

@@ -99,13 +99,17 @@ public abstract class LStatement{
                 //escape characters that would otherwise break out of the string or corrupt it.
                 for(int i = 1; i < value.length() - 1; i++){
                     char c = value.charAt(i);
-                    //exception: allow escape sequences in strings: \n, \", \\
+                    //exception: allow escape sequences in strings: \n, \", \\, uXXXX
                     if(c == '\\' && i + 1 < value.length() - 1){
                         char next = value.charAt(i + 1);
                         if(next == '"' || next == '\\' || next == 'n'){
                             res.append(c).append(next);
                             i ++; //consumed the escape target too
                             continue;
+                        }else if(next == 'u' && i + 5 < value.length() - 1 && isHex(value, i + 2)){
+                            res.append(value, i, i + 6);
+                            i += 5; //consumed u and the 4 hex digits too
+                            continue;
                         }
                     }
                     switch(c){
@@ -136,6 +140,14 @@ public abstract class LStatement{
         return value;
     }
 
+    /** True if the 4 characters at value[from..from+3] are all hex digits. */
+    private static boolean isHex(String value, int from){
+        for(int i = from; i < from + 4; i++){
+            if(Character.digit(value.charAt(i), 16) == -1) return false;
+        }
+        return true;
+    }
+
     protected static boolean logicLocalization(){
         return Core.settings.getBool("logiclocalization", true);
     }

tests/src/test/java/LogicTests.java

@@ -83,6 +83,21 @@ public class LogicTests{
         "escaped backslash sitting right before the closing quote",
         "set result \"end\\\\\"",
         "end\\"
+        ),
+        Arguments.of(
+        "\\u0041 decodes to the corresponding unicode character",
+        "set result \"\\u0041\"",
+        "A"
+        ),
+        Arguments.of(
+        "\\uf8ff decodes to the corresponding unicode character",
+        "set result \"\\uf8ff\\uf8ff\"",
+        ""
+        ),
+        Arguments.of(
+        "\\u escapes combined with other escapes in one string",
+        "set result \"\\u0041\\n\\u0042\\\\end\"",
+        "A\nB\\end"
         )
         );
     }
@@ -140,7 +155,32 @@ public class LogicTests{
         Arguments.of("a raw '#' in an unquoted value gets neutralized so it can't start a comment", "a#b", "a_b"),
         Arguments.of("a lone newline character is invalid on its own, same as a lone space", "\n", "invalid"),
         Arguments.of("a lone tab character is invalid on its own, same as a lone space", "\t", "invalid"),
-        Arguments.of("a lone '#' character is invalid on its own, same as a lone space", "#", "invalid")
+        Arguments.of("a lone '#' character is invalid on its own, same as a lone space", "#", "invalid"),
+        Arguments.of(
+        "a well-formed \\uXXXX escape inside a quoted value passes through untouched",
+        "\"\\u0041\"",
+        "\"\\u0041\""
+        ),
+        Arguments.of(
+        "\\uXXXX combined with other escapes inside a quoted value",
+        "\"\\u0041\\n\\u0042\\\\end\"",
+        "\"\\u0041\\n\\u0042\\\\end\""
+        ),
+        Arguments.of(
+        "a malformed \\u escape with too few digits still escapes the backslash instead of throwing",
+        "\"\\u12\"",
+        "\"\\\\u12\""
+        ),
+        Arguments.of(
+        "a malformed \\u escape with non-hex digits still escapes the backslash instead of throwing",
+        "\"\\u12zz\"",
+        "\"\\\\u12zz\""
+        ),
+        Arguments.of(
+        "a \\u escape truncated by the closing quote still escapes the backslash instead of throwing",
+        "\"a\\u123\"",
+        "\"a\\\\u123\""
+        )
         );
     }
 
@@ -232,6 +272,22 @@ public class LogicTests{
         Arguments.of(
         "a string that never closes before the line ends, with trailing content after it",
         "set result \"asd\nset bar 5"
+        ),
+        Arguments.of(
+        "a \\u escape with non-hex digits is rejected",
+        "set result \"\\u12zz\""
+        ),
+        Arguments.of(
+        "a \\u escape with non-hex digits is rejected",
+        "set result \"\\u1h23\""
+        ),
+        Arguments.of(
+        "a \\u escape with non-hex digits is rejected",
+        "set result \"\\uhh23\""
+        ),
+        Arguments.of(
+        "a \\u escape truncated by the closing quote is rejected",
+        "set result \"\\u12\""
         )
         );
     }