~technomancy/fennel#126: 
fennel.parser should take in a plugin list

Fennel, when used as a library, provides a number of functions in order to call various parts of the compiler. Most of these functions accept, inside an options table, an optional list of plugins that can affect the way the compiler works. Although plugins have the :parse-error hook that affects the way parsing works, the function fennel.parser does not accept a list of plugins. This means the only way to pass an argument to affect the parser is via a function like fennel.compileString which parses and compiles in the same call (I haven't actually verified if this option works), or by calling the compiler via command line and passing a plugin filename as an argument.

Ideally, fennel.parser would be able to simply use the :plugins key from its options table.

Status
RESOLVED IMPLEMENTED
Submitter
~xerool
Assigned to
No-one
Submitted
1 year, 8 months ago
Updated
1 year, 7 months ago
Labels
enhancement

~technomancy 1 year, 7 months ago

The reason this is slightly more complicated than it looks is that the plugins are accessed via the utils.hook function. This function does not take the plugins as arguments; instead it looks for them in utils.root which acts as a kind of cheap version of dynamic scope where for every compilation we set and unset the root values (chunk, options, and scope) when we enter and exit the compilation process. (This is why plugins assert-compile function has that final reset function arg; otherwise the root data doesn't get cleaned up.)

So when the parser calls utils.hook during the normal compilation process, it works fine. But when you call fennel.parser directly, there is no such "enter/exit" cycle for the root to be set. However, the point of the root is to avoid having to pass these values around everywhere, and within the parser, "everywhere" is not so big of a problem.

So the first step would be to make utils.hook accept an optional argument to check for a plugins table instead of the root, because the root is simply not a viable concept in fennel.parser. Problem is utils.hook takes ... so we can't add an optional argument. Maybe we can create a separate utils.hook-opts or something which takes options as an arg and change utils.hook to call it? Or update all the calls to utils.hook to pass in nil as its second argument before ....

~technomancy REPORTED IMPLEMENTED 1 year, 7 months ago

Thanks for the fix!

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