TransformationError: Node type 'GeneratorExp' [...] No transformation for the node

[joerick]

Hi there! This is a very interesting project to me, currently trying to assess if it will solve a problem I have.

When converting some files in my project, I get this error:

$ pj pyinstrument/frame.py
An error occurred while compiling source file 'pyinstrument/frame.py'
TransformationError: Node type 'GeneratorExp': Line: 306, column: 29. No transformation for the node

The line that it's referencing is this:

        calculated_time = sum(child.time for child in self.children) + self.absorbed_time

So I guess that's the generator expression. I use them a lot in this project. I guess it might translate like so?

        let calculated_time = this.children.map(child => child.time).reduce((a, b) => a+b) + this.absorbed_time

Is there a way to get these generator expressions to convert?

[azazel75]

Hi Joe, thanks for using JavaScripthon!

>>>> Joe Rickerby ***@***.***> writes:

Hi there! This is a very interesting project to me, currently trying to assess if it will solve a problem I have. When converting some files in my project, I get this error: ```sh $ pj pyinstrument/frame.py An error occurred while compiling source file 'pyinstrument/frame.py' TransformationError: Node type 'GeneratorExp': Line: 306, column: 29. No transformation for the node ``` eh, in general all the comprehensions aren't so well supported, I could choose to translate to a more recent version of JS that has a better support for those kind of code and drop ES5 completely, but with Javascript it isn't so easy to drop legacy stuff... Anyway, there's at least two things I can suggest you: The line that it's referencing is this: ```python calculated_time = sum(child.time for child in self.children) + self.absorbed_time ``` if you convert it to: ```python calculated_time = sum([child.time for child in self.children]) + self.absorbed_time ``` then it works: ```sh $ nix run . -- -s - calculated_time = sum([child.time for child in self.children]) + self.absorbed_time var calculated_time; calculated_time = (sum(function () { var _pj_a = [], _pj_b = this.children; for (var _pj_c = 0, _pj_d = _pj_b.length; (_pj_c < _pj_d); _pj_c += 1) { var child = _pj_b[_pj_c]; _pj_a.push(child.time); } return _pj_a; } .call(this)) + this.absorbed_time); ``` as you can see the code isn't so elegant, all the translation could have a more modern cut, but unfortunately I don't use pj so frequently anymore... I'm also wondering if that code does the right thing, with the use of `this`, you will have to try... So I guess that's the generator expression. I use them a lot in this project. I guess it might translate like so? ```js let calculated_time = this.children.map(child => child.time).reduce((a, b) => a+b) + this.absorbed_time ``` Is there a way to get these generator expressions to convert? There's no way that the translator could come up doing such conversion from a sum of a sequence to the reduction using a '+' binary operation without having a dedicated translator function that maps the two. -- Alberto Berti - Information Technology Consultant PGP: 9377 A68C C5B5 B534 36BD F20B E3B5 C559 99D6 7CF9 "gutta cavat lapidem"

[joerick]

Ah, yeah, that might work. I almost think that, given generator expressions don't exist in JS, there's always gonna be an array involved so maybe it should always output an array for such an expression - at least, it seems better than failing.

I'll do some more experimentation!