Command line parser respects outer escaped quote

Author: som-snytt

compiler/src/dotty/tools/dotc/config/CommandLineParser.scala

@@ -29,6 +29,7 @@ object CommandLineParser:
     inline def bump() = pos += 1
     inline def done   = pos >= line.length
 
+    // Skip to the next quote as given; false on no more input.
     def skipToQuote(q: Int): Boolean =
       var escaped = false
       def terminal = cur match
@@ -39,13 +40,18 @@ object CommandLineParser:
       while !terminal do bump()
       !done
 
-    @tailrec def skipToDelim(): Boolean =
+    // Skip to a word boundary, where words can be quoted and quotes can be escaped; false on missing quote.
+    def skipToDelim(): Boolean =
+      var escaped = false
       inline def quote() = { qpos += pos ; bump() }
-      cur match
+      def advance(): Boolean = cur match
+        case _ if escaped         => escaped = false ; bump() ; advance()
+        case '\\'                 => escaped = true ; bump() ; advance()
         case q @ (DQ | SQ)        => { quote() ; skipToQuote(q) } && { quote() ; skipToDelim() }
         case -1                   => true
         case c if isWhitespace(c) => true
         case _                    => bump(); skipToDelim()
+      advance()
 
     def copyText(): String =
       val buf = new java.lang.StringBuilder
@@ -74,7 +80,7 @@ object CommandLineParser:
 
     inline def badquote() = errorFn(s"Unmatched quote [${qpos.last}](${line.charAt(qpos.last)})")
 
-    inline def skipWhitespace() = while isWhitespace(cur) do pos += 1
+    inline def skipWhitespace() = while isWhitespace(cur) do bump()
 
     @tailrec def loop(): List[String] =
       skipWhitespace()
@@ -85,7 +91,7 @@ object CommandLineParser:
         badquote()
         Nil
       else
-        accum = text() :: accum
+        accum ::= text()
         loop()
     end loop
 

compiler/test/dotty/tools/dotc/config/CommandLineParserTest.scala

@@ -44,3 +44,9 @@ class CommandLineParserTest:
     // missing quotes
     checkFails(""""x""", "Unmatched quote [0](\")")  // was assertEquals(List("\"x"), tokenize(""""x"""))
     checkFails("""x'""", "Unmatched quote [1](')")
+
+  @Test def `leading quote is escaped`: Unit =
+    check("echo", """\"hello""", """world!\"""")("""echo \"hello world!\" """)
+    check("""a\"b\"c""")("""a\"b\"c""")
+    check("a", "\\'b", "\\'", "c")("""a \'b \' c""")
+    check("a", "\\\\b ", "c")("""a \\'b ' c""")