CODEWITHSUNDEEP
pegpegjs
Stefan Stoychev
Stefan Stoychev

Reputation: 5012

Use PEG.js generated parser to beautify code

I want to create a formatter/linter for a custom program language and was reading about it but seems that im missing something.

Was looking/playing with PEG.js and seems that it will do the work. Ive wrote a small parser and when ran - it correctly returns the syntax tree (AST)

And the main question now is: how to use the generated parser to create (for example) a VSCode/Atom/CodeMirror/etc. extension(s) that will beautify/format the code?

Is this the right approach in general? (using a parser or need to write specific parsers for each tool)

Upvotes: 0

Views: 307

Answers (1)

JDB
JDB

Reputation: 25810

Beautifying code is basically just converting the AST back into code, throwing away the original white space and replacing it with the desired formatting.

The following grammar converts a list of case-insensitive a characters into an array:

Expression = _ array:( a:"a"i _ {return a} )+ _ {return array}
_ = [ \t\n]*

So given this input:

aa
aaaAa

a

You get this output:

[
   "a",
   "a",
   "a",
   "a",
   "a",
   "A",
   "a",
   "a"
]

To "beautify" this list, you'd simply convert the array back into a list, except with a more regular spacing:

result.join(" ");
// produces "a a a a a A a a", which is syntactically identical

Upvotes: 2

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