Feature #20210: Invalid source encoding raises ArgumentError, not SyntaxError

• Status: Closed
• Assignee: -
• Target version: -

[kddnewton (Kevin Newton)]

I was hoping we could change the error that is raised when an invalid source encoding is found from an ArgumentError to a SyntaxError.

First let me say, if this isn't possible for backward compatibility, I understand. Please do not take this as me not caring about backward compatibility.

Right now, if you have the script # encoding: foo\n"bar", it will raise an ArgumentError, not a SyntaxError. If there are other syntax errors in the file, there's no way to concat them together to give feedback to the user. If a user wants to consistently handle the errors coming back from a parse, they currently have to rescue ArgumentError and SyntaxError.

Ideally it would all be SyntaxError, so we could handle them consistently and append all errors together.

[nobu (Nobuyoshi Nakada)]

• Tracker changed from Misc to Feature

I don't remember the reason to select ArgumentError, SyntaxError feels more reasonable.
https://github.com/ruby/ruby/pull/9701

[yui-knk (Kaneko Yuichiro)]

I'm wondering which encoding should be used if the parser hits invalid source encoding like # coding: foo. I think it's needed to clarify which encoding is assumed on this ticket.

[naruse (Yui NARUSE)]

Parsing entire source code with wrong encoding is not reasonable because in some encoding including SJIS (Windows-31J) parsing result won't be valid because some multibyte character may include ASCII character in the trailing byte in the encoding. A developer need to fix the encoding first.

[Edwing123 (Edwin Garcia)]

Hi. One question:

When parsing begins, what encoding do Prism and parse.y use by default?

[kddnewton (Kevin Newton)]

@naruse (Yui NARUSE) I'm fine exiting immediately, I was just hoping to make it a syntax error.

@Edwing123 (Edwin Garcia) By default Ruby source assumes UTF-8 unless told otherwise by a magic comment or a command line option.

[mame (Yusuke Endoh)]

Discussed at the dev meeting.

We need a good reason to introduce incompatibility. You say you are fine with the current behavior (exiting immediately), Then, we can't see no reason to change it.

This is just my idea: it would be great for prism, as a library, to continue parsing even with an invalid encoding magic comment (maybe as ASCII-8BIT?), but it would be good to keep the behavior of Ruby interpreter as possible.

[kddnewton (Kevin Newton)]

• Status changed from Open to Closed

I think that makes sense! Let's keep it as an argument error. Prism will keep parsing for now, but raise the right error.