How to use different parsers with one input text to make an AST?

[nathantetro]

Hi Chevrotain community

I am trying to make my own simple version of React using Chevrotain.

So far I have a parser that can recognize some grammar rules for function declaration, import statement and so on.
To make a CST with the parser, you have to start from a rule. Thus, I've made a couple of parsers starting from different rules.
For example: importStatementParser, componentDeclarationParser, and so on.

Now my question is:
If I get 1 input string (for example: " import x from 'y'; let a = 5; "), how do I know which of the parsers to apply to the different parts of the string?

I'm really stuck here.

[bd82]

Hello @nathantetro

If I get 1 input string (for example: " import x from 'y'; let a = 5; "), how do I know which of the parsers to apply to the different parts of the string?

There is normally some root rule that iterates on these sub-rules of the different parts. e.g:

• chevrotain/examples/grammars/tinyc/tinyc.js

  Lines 57 to 61 in efbc5da

  	$.RULE("program", () => {
  	$.MANY(() => {
  	$.SUBRULE($.statement)
  	})
  	})

E.g in Java a program may be:

• package declaration
• followed by import declarations
• followed by class declarations.

This is actually defined in the Java Grammar and would be your root rule if you were implementing a Parser for Java...

[nathantetro]

Hi @bd82

Working with a root rule worked for me. Thanks for helping out! :)