ICU-22898 MF2 parser bug fixes

ICU4C: Escape curly braces when serializing and normalizing
ICU4C: Escape '|' in patterns
ICU4C: When normalizing input, escape optionally-escaped characters in patterns
ICU4C/ICU4J: Allow trailing whitespace after a match
ICU4C: Fix parser to iterate over code points, not code units
Add tests with old reserved syntax as syntax-error tests

icu4c/source/i18n/messageformat2_parser.h

@@ -140,10 +140,21 @@ namespace message2 {
 	SelectorKeys parseNonEmptyKeys(UErrorCode&);
 	void errorPattern(UErrorCode& status);
 	Pattern parseQuotedPattern(UErrorCode&);
+        bool isDeclarationStart();
+
+        UChar32 peek() const { return source.char32At(index) ; }
+        UChar32 peek(uint32_t i) const {
+            return source.char32At(source.moveIndex32(index, i));
+        }
+        void next() { index = source.moveIndex32(index, 1); }
+
+        bool inBounds() const { return (int32_t) index < source.length(); }
+        bool inBounds(uint32_t i) const { return source.moveIndex32(index, i) < source.length(); }
+        bool allConsumed() const { return (int32_t) index == source.length(); }
 
 	// The input string
 	const UnicodeString &source;
-	// The current position within the input string
+	// The current position within the input string -- counting in UChar32
 	uint32_t index;
 	// Represents the current line (and when an error is indicated),
 	// character offset within the line of the parse error

icu4c/source/i18n/messageformat2_serializer.cpp

@@ -42,24 +42,26 @@ void Serializer::emit(const std::u16string_view& token) {
 void Serializer::emit(const Literal& l) {
     if (l.isQuoted()) {
       emit(PIPE);
-      const UnicodeString& contents = l.unquoted();
-      for (int32_t i = 0; i < contents.length(); i++) {
-        // Re-escape any PIPE or BACKSLASH characters
+    }
+    const UnicodeString& contents = l.unquoted();
+    for (int32_t i = 0; ((int32_t) i) < contents.length(); i++) {
+        // Re-escape any escaped-char characters
         switch(contents[i]) {
         case BACKSLASH:
-        case PIPE: {
-          emit(BACKSLASH);
-          break;
+        case PIPE:
+        case LEFT_CURLY_BRACE:
+        case RIGHT_CURLY_BRACE: {
+            emit(BACKSLASH);
+            break;
         }
         default: {
-          break;
+            break;
         }
         }
         emit(contents[i]);
-      }
-      emit(PIPE);
-    } else {
-      emit(l.unquoted());
+    }
+    if (l.isQuoted()) {
+        emit(PIPE);
     }
 }
 
@@ -194,9 +196,10 @@ void Serializer::emit(const PatternPart& part) {
     if (part.isText()) {
         // Raw text
         const UnicodeString& text = part.asText();
-        // Re-escape '{'/'}'/'\'
-        for (int32_t i = 0; i < text.length(); i++) {
+        // Re-escape '{'/'}'/'\''|'
+        for (int32_t i = 0; ((int32_t) i) < text.length(); i++) {
           switch(text[i]) {
+          case PIPE:
           case BACKSLASH:
           case LEFT_CURLY_BRACE:
           case RIGHT_CURLY_BRACE: {

icu4c/source/test/intltest/messageformat2test_read_json.cpp

@@ -303,6 +303,8 @@ void TestMessageFormat2::jsonTestsFromFiles(IcuTestErrorCode& errorCode) {
     // Do tests for reserved statements/expressions
     runTestsFromJsonFile(*this, "spec/unsupported-expressions.json", errorCode);
     runTestsFromJsonFile(*this, "spec/unsupported-statements.json", errorCode);
+    // Uncomment when reserved syntax is removed
+    // runTestsFromJsonFile(*this, "syntax-errors-reserved.json", errorCode);
 
     // Do valid spec tests
     runTestsFromJsonFile(*this, "spec/syntax.json", errorCode);

icu4j/main/core/src/main/java/com/ibm/icu/message2/MFParser.java

@@ -613,10 +613,8 @@ public class MFParser {
             }
             keys.add(key);
         }
-        // Only want to skip whitespace if we parsed at least one key
-        if (!keys.isEmpty()) {
-            skipOptionalWhitespaces();
-        }
+        // Trailing whitespace is allowed after the message
+        skipOptionalWhitespaces();
         if (input.atEnd()) {
             checkCondition(
                     keys.isEmpty(), "After selector keys it is mandatory to have a pattern.");

icu4j/main/core/src/test/java/com/ibm/icu/dev/test/message2/CoreTest.java

@@ -40,6 +40,7 @@ public class CoreTest extends CoreTestFmwk {
                                                 "syntax-errors-diagnostics.json",
                                                 "syntax-errors-diagnostics-multiline.json",
                                                 "syntax-errors-end-of-input.json",
+                                                "syntax-errors-reserved.json",
                                                 "tricky-declarations.json",
                                                 "valid-tests.json"};
 

testdata/message2/syntax-errors-diagnostics.json

@@ -136,11 +136,6 @@
         "char": 28,
         "comment": "Trailing characters that are not whitespace"
     },
-    {
-        "src": ".match {$foo :string} {$bar :string}  one * {{one}}  * * {{other}}   ",
-        "char": 66,
-        "comment": "Trailing whitespace at end of message should not be accepted either"
-    },
     {
         "src": "empty { }",
         "char": 8,
@@ -343,6 +338,10 @@
         "src":  ".match {1} {{_}}",
         "char": 12,
         "comment": "Disambiguating a wrong .match from an unsupported statement"
+    },
+    {
+        "src": "{{{/p o4.􍅲 = 1}}}",
+        "char": 9
     }
   ]
 }

testdata/message2/syntax-errors-reserved.json

@@ -0,0 +1,22 @@
+{
+  "scenario": "Reserved and private annotations",
+  "description": "Tests for old unsupported expression (reserved/private) syntax -- these are now syntax errors",
+  "defaultTestProperties": {
+    "locale": "en-US",
+    "expErrors": [
+        {
+        "type": "syntax-error"
+      }
+    ]
+  },
+  "tests": [
+      { "src" : "\\\\{   ?   󗟋   𫓜|@}   |}" },
+      { "src" : "\\\\{   ?   󗟋   𫓜|@}   |   \\}   @𠟅򑚎𥪙𽧫=||   @򒘒򳷦㥞򉊷=$򸚶񽱆񅗽񤕞   @𰺱:񎫛񢶛򶈎񄮒}" },
+      { "src" : "{  $iFN  ^  @USh  =$u  @l}" },
+      { "src" : ".local $dS ={ $p4 ^ |.| \\\\ @g:FV = $kd}{{@}}" },
+      { "src" : ".D. \\\\ ||{1}{{}} " },
+      { "src" : ".cIT  ||{|@|  %  \\}  }  {  *󔜫񥘃󸇀  }{{}}" },
+      { "src" : ".򱋿󠆿 . |@| {$󛒁񓝖 & \\{ . @𯼼򋼡= $򵀀񓞈}{{\\\\}}" }
+  ]
+}
+

testdata/message2/valid-tests.json

@@ -123,6 +123,34 @@
       "comment": "message -> complex-message -> *(declaration [s]) complex-body -> declaration complex-body -> input-declaration complex-body -> input variable-expression complex-body",
       "src": ".input{$x}{{}}",
       "exp": ""
+    },
+    {
+      "comment": "Test that escaped characters are re-escaped properly when serializing literals",
+      "src": "{|\\}|}",
+      "exp": "}"
+    },
+    {
+      "comment": "Test that escaped characters are re-escaped properly when serializing patterns",
+      "src": "\\|",
+      "exp": "|"
+    },
+    {
+      "comment": "Test that parser and serializer treat optionally-escaped characters consistently",
+      "src" : "{{{1}|}}",
+      "exp": "1|"
+    },
+    {
+      "comment": "Trailing whitespace after match is valid",
+      "src": ".match {1 :string} * {{}} ",
+      "exp": ""
+    },
+    {
+      "src" : "𴢸",
+      "exp" : "𴢸"
+    },
+    {
+      "src" : "{{􍅲}}",
+      "exp" : "􍅲"
     }
   ]
 }