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fix: unpaired apostrophe in JavaScript comments #370

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fix: unpaired apostrophe in JavaScript comments #370

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ccd2f84
fix: unpaired apostrophe in JavaScript comments
rtritto Jun 4, 2026
b335b27
fix unpaired apostrophes within comments, and specific line terminato…
rtritto Jun 4, 2026
038fd66
hoisting the line-terminator regex outside the loop/function scope
rtritto Jun 4, 2026
c29c0ac
simplify the CRLF handling of the regex
rtritto Jun 4, 2026
bc1e1d1
add tests
rtritto Jun 5, 2026
34d8d6b
fix: handle unpaired apostrophes and improve closing tag parsing in c…
rtritto Jul 14, 2026
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14 changes: 13 additions & 1 deletion src/parse.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,8 @@ const singleQuoteReg = /'(?:\\[\s\w"'\\`]|[^\n\r'\\])*?'/g;

const doubleQuoteReg = /"(?:\\[\s\w"'\\`]|[^\n\r"\\])*?"/g;

const lineTerminatorReg = /(?:\r\n|[\n\r\u2028\u2029])/g;

@jayaddison jayaddison Jun 22, 2026

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This makes me think that we might be missing the U+2028 / U+2029 line terminators from the end-quote regex patterns (singleQuoteReg, doubleQuoteReg). I haven't explored this yet but would like to.

@jayaddison jayaddison Jun 22, 2026

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The regex itself seems correct to me. There might be a way to use the /.*/ pattern as an optimisation later; that should match on everything except for line terminators -- which are exactly the set of things this regex searches for.

The regex consumes CRLF when it is found, which is potentially helpful, because it'll move the search needle entirely past the linebreak to the following line's content.. although makes the code slightly less platform-agnostic.


/** Escape special regular expression characters inside a string */

function escapeRegExp(string: string) {
Expand Down Expand Up @@ -109,7 +111,9 @@ export function parse(this: Eta, str: string): Array<AstObject> {
);

const parseCloseReg = new RegExp(
"'|\"|`|\\/\\*|(\\s*(-|_)?" + escapeRegExp(config.tags[1]) + ")",
"'|\"|`|\\/\\*|(\\s*(-|_)?" +
escapeRegExp(config.tags[1]) +
")|\\/\\/",
"g",
);

Expand Down Expand Up @@ -161,6 +165,14 @@ export function parse(this: Eta, str: string): Array<AstObject> {
ParseErr("unclosed comment", str, closeTag.index);
}
parseCloseReg.lastIndex = commentCloseInd;
} else if (char === "//") {
lineTerminatorReg.lastIndex = parseCloseReg.lastIndex;
const match = lineTerminatorReg.exec(str);
if (match) {
parseCloseReg.lastIndex = match.index + match[0].length;
} else {
parseCloseReg.lastIndex = str.length;
}
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} else if (char === "'") {
singleQuoteReg.lastIndex = closeTag.index;

Expand Down
44 changes: 44 additions & 0 deletions test/parse.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,22 @@ describe("parse test", () => {
]);
});

it("works with unpaired apostrophe in single-line comment", () => {
const buff = eta.parse("hi <% // comment with unpaired apostrophe' \n %>");

@jayaddison jayaddison Jun 22, 2026

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One more request for a test case: please could we add a (negative) test case where a single-line comment extends all the way to the end of the template?

In other words, something like:

const buff = eta.parse("hi <% // comment with unpaired apostrophe'");

This should raise an unclosed tag parse error exception.

The reason I'm asking: I think it might be possible to break out of one of the loops as a potential optimisation, at a later date. But let's add test coverage on the scenario to confirm the behaviour, before doing that.

expect(buff).toEqual([
"hi ",
{ val: "// comment with unpaired apostrophe' \n", t: "e" },
]);
});

it("works with unpaired apostrophe in multiline comment", () => {
const buff = eta.parse("hi <% /* comment with unpaired apostrophe' */ %>");

@jayaddison jayaddison Jun 22, 2026

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@rtritto your fix works for double-quotes in addition to apostrophes, and I think that might be worth demonstrating too.

Another set of scenarios I'll look into is cases where there are mixed // and /* comments, including interleaving of those (for example -- start /* // middle */ end).

expect(buff).toEqual([
"hi ",
{ val: "/* comment with unpaired apostrophe' */", t: "e" },
]);
});

it("parses with simple template literal", () => {
// biome-ignore lint/suspicious/noTemplateCurlyInString: intentional
const buff = eta.parse("hi <%= `template %> ${value}` %>");
Expand Down Expand Up @@ -114,4 +130,32 @@ describe("parse test", () => {
<%= /* %>
^`);
});

it("handles alternative closing tags properly, rather than confusing them with comments", () => {
const originalEta = new Eta({ tags: ["{{", "//"] });
const buff = originalEta.parse("{{= it.x//");
expect(buff).toEqual([{ val: "it.x", t: "i" }]);
const originalEta2 = new Eta({ tags: ["{{", "//}}"] });
const buff2 = originalEta2.parse("{{= it.x//}}");
expect(buff2).toEqual([{ val: "it.x", t: "i" }]);
});

it("handles various line termination characters in single-line comments", () => {
const cases = ["\r", "\r\n", "\u2028", "\u2029", "\n"];
for (const terminator of cases) {
const buff = eta.parse(`hi <% // comment ending with terminator${terminator} %>`);
expect(buff).toEqual([
"hi ",
{ val: `// comment ending with terminator${terminator}`, t: "e" },
]);
}
});

it("handles a sequence looking like close tag inside single line comment", () => {
const buff = eta.parse("hi <% // comment %> with close tag\n %>");
expect(buff).toEqual([
"hi ",
{ val: "// comment %> with close tag\n", t: "e" },
]);
});
});