attachComments doesn't attach comments found in function signature

[medikoo]

Code:

var x = function (/* signature comment */) {
    return 'foo' + 'bar';
};
/* raz */
x(function (other) { return other });

Handling:

var ast = esprima.parse(code, { comment: true, range: true, tokens: true });
console.log(ast.comments.length); // 2, both comments are referenced
ast = escodegen.attachComments(ast, ast.comments, ast.tokens);
console.log(escodegen.generate(ast, { comment: true });

Result:

var x = function (foo) {
    return 'foo' + 'raz'
};
/* raz */
x(function (other) {
    return other
})

We miss comment in function signature

[Constellation]

This is the issue of escodegen.
Since currently escodegen only supports Statement level comment, escodegen drops these comments.
Please file it to escodegen.

[medikoo]

@Constellation I don't see it so. attachComments is etraverse method, just referenced by escodegen,

estraverse.attachComments do not attach all comments as expected. Let me fix above example to use estraverse directly

[medikoo]

Exact example with output:
example.js

var x = function (/* signature comment */) {
    return 'foo' + 'bar';
};
/* raz */
x(function (other) { return other });

test.js

var esprima    = require('esprima')
  , estraverse = require('estraverse')
  , inspect    = require('util').inspect

  , code = require('fs').readFileSync(__dirname + '/example.js')
  , inspectOpts = { depth: 10, colors: true };

var ast = esprima.parse(code, { comment: true, range: true, tokens: true });

console.log("Comments", inspect(ast.comments, inspectOpts)); // All comments there

ast = estraverse.attachComments(ast, ast.comments, ast.tokens);

console.log("Attached?: ", inspect(ast.body, inspectOpts)); // No comments attached

After running above, with latest node, and latest versions of involved packages, you get following output:

Comments in AST as generated by esprima:

Comments [ { type: 'Block',
    value: ' signature comment ',
    range: [ 18, 41 ] },
  { type: 'Block',
    value: ' raz ',
    range: [ 71, 80 ] } ]

AST after comments being attached:

Attached?:  [ { type: 'VariableDeclaration',
    declarations: 
     [ { type: 'VariableDeclarator',
         id: 
          { type: 'Identifier',
            name: 'x',
            range: [ 4, 5 ] },
         init: 
          { type: 'FunctionExpression',
            id: null,
            params: [],
            defaults: [],
            body: 
             { type: 'BlockStatement',
               body: 
                [ { type: 'ReturnStatement',
                    argument: 
                     { type: 'BinaryExpression',
                       operator: '+',
                       left: 
                        { type: 'Literal',
                          value: 'foo',
                          range: [ 53, 58 ] },
                       right: 
                        { type: 'Literal',
                          value: 'bar',
                          range: [ 61, 66 ] },
                       range: [ 53, 66 ] },
                    range: [ 46, 67 ] } ],
               range: [ 43, 69 ] },
            rest: null,
            generator: false,
            expression: false,
            range: [ 8, 69 ] },
         range: [ 4, 69 ] } ],
    kind: 'var',
    range: [ 0, 70 ] },
  { type: 'ExpressionStatement',
    expression: 
     { type: 'CallExpression',
       callee: 
        { type: 'Identifier',
          name: 'x',
          range: [ 81, 82 ] },
       arguments: 
        [ { type: 'FunctionExpression',
            id: null,
            params: 
             [ { type: 'Identifier',
                 name: 'other',
                 range: [ 93, 98 ] } ],
            defaults: [],
            body: 
             { type: 'BlockStatement',
               body: 
                [ { type: 'ReturnStatement',
                    argument: 
                     { type: 'Identifier',
                       name: 'other',
                       range: [ 109, 114 ] },
                    range: [ 102, 115 ] } ],
               range: [ 100, 116 ] },
            rest: null,
            generator: false,
            expression: false,
            range: [ 83, 116 ] } ],
       range: [ 81, 117 ] },
    range: [ 81, 118 ],
    leadingComments: 
     [ { type: 'Block',
         value: ' raz ',
         range: { '0': 71, '1': 80 },
         extendedRange: [ 70, 81 ] } ] } ]

You can clearly see, that signature comment was not attached by estraverse.attachComments as expected.

[medikoo]

So can you please clarify further, or reopen the issue

[Constellation]

Ah, I missed it. In this case,

var x = function (/* signature comment */) {
    return 'foo' + 'bar';
};
/* raz */
x(function (other) { return other })

We cannot attach /* signature comment */ to some nodes since there's no reasonable leading or trailing node for this comment.
This is severe problem, we're discussing about this on escodegen#133.
/cc @getify @michaelficarra

[medikoo]

@Constellation it's only the case if there are no arguments in signature, it all works fine if there is at least one argument, e.g. for following function (/* foo */arg/* bar */) {} arguments will be attached properly.

So is there any chance to have that reopened?

[Constellation]

Reopened.

@Constellation it's only the case if there are no arguments in signature, it all works fine if there is at least one argument, e.g. for following function (/* foo /arg/ bar */) {} arguments will be attached properly.

Right. In this case (there are no arguments), currently I don't have reasonable way to solve this.
We cannot handle the following patterns too.

(function /* comment */ () { });

[gfranko]

Is there any update on this?