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JavaScript: Handle E4X/Flow lexical ambiguity.

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This commit is contained in:
Max Schaefer
2019-02-04 14:53:38 +00:00
parent d6deefed86
commit c7e428eb27
3 changed files with 254 additions and 5 deletions
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23
javascript/extractor/src/com/semmle/jcorn/CustomParser.java
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@@ -546,12 +546,21 @@ public class CustomParser extends FlowParser {
@Override
protected Token readToken(int code) {
// skip XML processing instructions (which are allowed in E4X, but not in JSX)
// skip XML processing instructions (which are allowed in E4X, but not in JSX);
// there is a lexical ambiguity between an XML processing instruction starting a
// chunk of E4X content and a Flow type annotation (both can start with `<?`)
// hence if we can't find the closing `?>` of a putative XML processing instruction
// we backtrack and try lexing as something else
if (this.options.e4x()) {
while (code == '<') {
if (charAt(this.pos+1) == '?') {
int oldPos = this.pos;
this.pos += 2;
jsx_readUntil("?>");
if (!jsx_readUntil("?>")) {
// didn't find a closing `?>`, so backtrack
this.pos = oldPos;
break;
}
} else {
break;
}
@@ -564,7 +573,10 @@ public class CustomParser extends FlowParser {
@Override
protected Either<Integer, Token> jsx_readChunk(StringBuilder out, int chunkStart, int ch) {
// skip XML comments, processing instructions and CDATA (which are allowed in E4X, but not in JSX)
// skip XML comments, processing instructions and CDATA (which are allowed in E4X,
// but not in JSX)
// unlike in `readToken` above, we know that we're inside JSX/E4X code, so there is
// no ambiguity with Flow type annotations
if (this.options.e4x() && ch == '<') {
if (inputSubstring(this.pos+1, this.pos+4).equals("!--")) {
out.append(inputSubstring(chunkStart, this.pos));
@@ -589,15 +601,16 @@ public class CustomParser extends FlowParser {
return super.jsx_readChunk(out, chunkStart, ch);
}
private void jsx_readUntil(String terminator) {
private boolean jsx_readUntil(String terminator) {
char fst = terminator.charAt(0);
while (this.pos+terminator.length() <= this.input.length()) {
if (charAt(this.pos) == fst &&
inputSubstring(this.pos, this.pos+terminator.length()).equals(terminator)) {
this.pos += terminator.length();
break;
return true;
}
++this.pos;
}
return false;
}
}