Require Line Terminator After Opening Text Block Delimiter

Salesforce requires the opening ''' of a triple-quoted text block to be
immediately followed by a line terminator; no other character, not even
whitespace, may appear before it. The single-line form '''hello''' is
rejected by the Apex compiler with "was expecting '\n'", so apexfmt
must not accept it either.

Update the TextBlockLiteral lexer rule to require an optional carriage
return and a mandatory line feed after the opening delimiter, and
regenerate the lexer. Add formatter tests covering rejection of the
single-line form, rejection of whitespace before the opening newline,
and round-tripping of a CRLF terminator.

Author: cwarden

formatter/text_block_test.go

@@ -377,6 +377,54 @@ func TestFormatter_MultipleTextBlockSwitchCases(t *testing.T) {
 	}
 }
 
+// TestFormatter_SingleLineTextBlockRejected asserts apexfmt rejects a
+// triple-quoted literal whose opening ”' is not immediately followed by a
+// line terminator. Salesforce requires the newline (reporting "was
+// expecting '\n'"), so the single-line form is not valid Apex and the
+// formatter must surface a parse error rather than silently accept it.
+func TestFormatter_SingleLineTextBlockRejected(t *testing.T) {
+	input := "public class Foo {\n" +
+		"\tpublic static String s = '''hello''';\n" +
+		"}\n"
+	f := NewFormatter("", strings.NewReader(input))
+	if err := f.Format(); err == nil {
+		t.Fatalf("expected a parse error for a single-line text block, got none")
+	}
+}
+
+// TestFormatter_WhitespaceBeforeOpeningNewlineRejected asserts that even
+// whitespace between the opening ”' and the line terminator is rejected,
+// matching Salesforce, which allows no character — not even a space — before
+// the required newline.
+func TestFormatter_WhitespaceBeforeOpeningNewlineRejected(t *testing.T) {
+	input := "public class Foo {\n" +
+		"\tpublic static String s = '''   \n" +
+		"hello''';\n" +
+		"}\n"
+	f := NewFormatter("", strings.NewReader(input))
+	if err := f.Format(); err == nil {
+		t.Fatalf("expected a parse error for whitespace before the opening newline, got none")
+	}
+}
+
+// TestFormatter_CRLFAfterOpeningDelimiterRoundTrips asserts that a CRLF line
+// terminator immediately after the opening ”' satisfies the requirement and
+// the block is preserved verbatim.
+func TestFormatter_CRLFAfterOpeningDelimiterRoundTrips(t *testing.T) {
+	input := "public class Foo {\n" +
+		"\tpublic static String s = '''\r\n" +
+		"hello''';\n" +
+		"}\n"
+	f := NewFormatter("", strings.NewReader(input))
+	if err := f.Format(); err != nil {
+		t.Fatalf("Format() failed for CRLF after opening delimiter: %v", err)
+	}
+	got := string(f.formatted)
+	if got != input {
+		t.Fatalf("CRLF text block was altered\nwant:\n%q\n got:\n%q", input, got)
+	}
+}
+
 // TestFormatter_TextBlockInsideIndentedMethodBody is the end-to-end
 // regression: a text block nested inside two levels of block indentation
 // must come out with the surrounding code re-indented normally but its

grammar/ApexLexer.g4

@@ -330,12 +330,14 @@ BooleanLiteral
 
 // Triple-quoted (multi-line) string literal. Must be matched before
 // StringLiteral so the longest-match rule picks it up on inputs that
-// start with three single quotes. The content allows backslash-escaped
-// characters (including an escaped ''' sequence via \''' and an explicit
-// line continuation \<line-terminator>); non-greedy '.*?' stops at the
-// first unescaped ''' triple.
+// start with three single quotes. Salesforce requires the opening '''
+// to be immediately followed by a line terminator (LF or CRLF); no other
+// character — not even whitespace — may appear before it. The content
+// allows backslash-escaped characters (including an escaped ''' sequence
+// via \''' and an explicit line continuation \<line-terminator>);
+// non-greedy '.*?' stops at the first unescaped ''' triple.
 TextBlockLiteral
-    :   '\'\'\'' ( '\\' . | ~[\\] )*? '\'\'\''
+    :   '\'\'\'' '\r'? '\n' ( '\\' . | ~[\\] )*? '\'\'\''
     ;
 
 StringLiteral