Inserted string validation as separate task in compiler.

frog/leg/string_validator.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Check the validity of string literals.
+
+#library("stringvalidator");
+
+#import("scanner/scannerlib.dart");
+#import("tree/tree.dart");
+#import("elements/elements.dart");
+#import("util/characters.dart");
+
+class StringValidator  {
+  final Canceler canceler;
+
+  StringValidator(this.canceler);
+
+  QuotedString validateQuotedString(Token token) {
+    SourceString source = token.value;
+    StringQuoting quoting = quotingFromString(source);
+    int leftQuote = quoting.leftQuoteLength;
+    int rightQuote = quoting.rightQuoteLength;
+    SourceString content = source.copyWithoutQuotes(leftQuote, rightQuote);
+    return validateString(token,
+                          token.charOffset + leftQuote,
+                          content,
+                          quoting);
+  }
+
+  QuotedString validateInterpolationPart(Token token, StringQuoting quoting,
+                                         [bool isFirst = false,
+                                          bool isLast = false]) {
+    SourceString source = token.value;
+    int leftQuote = 0;
+    int rightQuote = 0;
+    if (isFirst) leftQuote = quoting.leftQuoteLength;
+    if (isLast) rightQuote = quoting.rightQuoteLength;
+    SourceString content = source.copyWithoutQuotes(leftQuote, rightQuote);
+    return validateString(token,
+                          token.charOffset + leftQuote,
+                          content,
+                          quoting);
+  }
+
+  static StringQuoting quotingFromString(SourceString sourceString) {
+    Iterator<int> source = sourceString.iterator();
+    bool raw = false;
+    int quoteChar = source.next();
+    if (quoteChar == $AT) {
+      raw = true;
+      quoteChar = source.next();
+    }
+    assert(quoteChar === $SQ || quoteChar === $DQ);
+    // String has at least one quote. Check it if has three.
+    // If it only have two, the string must be an empty string literal,
+    // and end after the second quote.
+    bool multiline = false;
+    if (source.hasNext() && source.next() == quoteChar && source.hasNext()) {
+      assert(source.next() == quoteChar);
+      multiline = true;
+    }
+    return StringQuoting.get(quoteChar, raw, multiline);
+  }
+
+  void stringParseError(String message, Token token, int offset) {
+    canceler.cancel("$message @ $offset", token : token);
+  }
+
+  /**
+   * Validates the escape sequences and special characters of a string literal.
+   * Returns a QuotedString if valid, and null if not.
+   */
+  QuotedString validateString(Token token,
+                              int startOffset,
+                              SourceString string,
+                              StringQuoting quoting) {
+    // We only need to check for invalid x and u escapes, for line
+    // terminators in non-multiline strings, and for invalid Unicode
+    // scalar values (either directly or as u-escape values).
+    int length = 0;
+    int index = startOffset;
+    for(Iterator<int> iter = string.iterator(); iter.hasNext(); length++) {
+      index++;
+      int code = iter.next();
+      if (code === $BACKSLASH) {
+        if (quoting.raw) continue;
+        if (!iter.hasNext()) {
+          stringParseError("Incomplete escape sequence",token, index);
+          return null;
+        }
+        index++;
+        code = iter.next();
+        if (code === $x) {
+          for (int i = 0; i < 2; i++) {
+            if (!iter.hasNext()) {
+              stringParseError("Incomplete escape sequence", token, index);
+              return null;
+            }
+            index++;
+            code = iter.next();
+            if (!isHexDigit(code)) {
+              stringParseError("Invalid character in escape sequence",
+                               token, index);
+              return null;
+            }
+          }
+          // A two-byte hex escape can't generate an invalid value.
+          continue;
+        } else if (code === $u) {
+          int escapeStart = index - 1;
+          index++;
+          code = iter.next();
+          int value = 0;
+          if (code == $OPEN_CURLY_BRACKET) {
+            // expect 1-6 hex digits.
+            int count = 0;
+            index++;
+            code = iter.next();
+            do {
+              if (!isHexDigit(code)) {
+                stringParseError("Invalid character in escape sequence",
+                                 token, index);
+                return null;
+              }
+              count++;
+              value = value * 16 + hexDigitValue(code);
+              index++;
+              code = iter.next();
+            } while (code != $CLOSE_CURLY_BRACKET);
+            if (count > 6) {
+              stringParseError("Invalid character in escape sequence",
+                               token, index - (count - 6));
+              return null;
+            }
+          } else {
+            // Expect four hex digits, including the one just read.
+            for (int i = 0; i < 4; i++) {
+              if (i > 0) {
+                index++;
+                code = iter.next();
+              }
+              if (!isHexDigit(code)) {
+                stringParseError("Invalid character in escape sequence",
+                                 token, index);
+                return null;
+              }
+              value = value * 16 + hexDigitValue(code);
+            }
+          }
+          code = value;
+        }
+      }
+      // This handles both unescaped characters and the value of unicode
+      // escapes.
+      if (!isUnicodeScalarValue(code)) {
+        stringParseError(
+            "Invalid Unicode scalar value U+${code.toRadixString(16)}",
+            token, index);
+        return null;
+      }
+    }
+    // String literal successfully validated.
+    return new QuotedString(string, quoting, length);
+  }
+}