Comment ranges at wrong location

Try to run the following code in e.g. RunKit:

var meriyah = require("meriyah")
var escodegen = require("escodegen")
var esprima = require("esprima")

var code = `try{}//
finally{}

try{}
catch(e){}//
finally{}

{
try{}
catch(e){}//
finally{}
}
`;

var merComments = [];
var merTokens = [];
var merTree = meriyah.parse(code, {
    ranges: true,
    onComment: function(type, value, start, end) {
        type = type === 'SingleLine' ? 'Line' : 'Block';
        merComments.push({type: type, value: value, range: [start, end]});
    },
    onToken: function(type, start, end) {
        merTokens.push({ type: type, range: [start, end]});
    }
});

merTree = escodegen.attachComments(merTree, merComments, merTokens);
var merCode = escodegen.generate(merTree, { comment: true });

var espriTree = esprima.parse(code, { comment: true, range: true, tokens: true });
espriTree = escodegen.attachComments(espriTree, espriTree.comments, espriTree.tokens);
var espriCode = escodegen.generate(espriTree, { comment: true });

[merComments, espriTree.comments, merTree, espriTree, merCode, espriCode]

If you then compare the ranges in the comment array for both Meriyah and Esprima, then you will see the values are not the same (start is 2 under, end is 1 under). If you then look at the generated code, which are generated from the Meriyah and Esprima tree and compare them, then you will see the comments are placed at the wrong places from the Meriyah tree.

Generated code from Esprima tree

try {
}    //
finally {
}
try {
} catch (e) {
}    //
finally {
}
{
    try {
    } catch (e) {
    }    //
    finally {
    }
}

Generated code from Meriyah tree

try {
} finally
    //
    {
    }
try {
} catch (e) {
}    //
finally {
}
{
    try {
    } catch (e) {
    }    //
    finally {
    }
}

-Thomas

[3cp]

That’s a weird spec, it’s different from comment in html format. Since the spec says

SingleLineHTMLCloseComment::
LineTerminatorSequenceHTMLCloseComment

I will make the start of HTMClose comment before “\n–>”

// For Single, start before "//",
// For HTMLOpen, start before "<!--",
// For HTMLClose, start before "\n-->"

[KFlash]

HTML comment is part of the AnnexB extension. Same as other parsers. HTML comment skips either <!-- or --> and then parsed as a single line comment.