Code completion about jsonata HOT 6 CLOSED

Hi - this is an interesting topic. I briefly looked at this a while back for the jsonata exerciser, which uses CodeMirror for the editor panels. Although it wouldn't be part of the core jsonata runtime, a component that supports code completion would be a really useful addition, especially if written in a way that could be plugged into different editor frameworks.

It would be great if you are interested in working on this. I'm not familiar with peg.js, although I do have some experience with BNF grammars. However, the JSONata parser is not generated from a BNF grammar but rather hand coded using Pratt's top-down operator precedence algorithm (see here for an excellent description). The code for it is here and the relative operator precedences are defined here. I imagine a grammar could be derived from this. Let me know if you need anything.

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Hmm, as I expected, the code and operator precedences are a bit too off to make a grammar file from. That leaves me two options:

1. Modify the jsonata source particularly in the evaluateVariable and evaluateLiteral functions and somehow lookup the schemas from there. I have some experience building a code completion this way and found that it is quite intrusive:-(

2. Use the JMESpath grammar, which should be similar, add the missing pieces on top. Much less intrusive but unsure how to organize the output structuring.

Give me a hint if you have any of these sounds better.
Cheers
Martin

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I added a simple code completion that can be seen in this repo: github. The error messages are enhanced with a proposal object. Check out the tests.

It uses a framework object to decide how the proposals are used. In this case it is a json schema. Only the source has code completion, for target we can use a normal json schema tool, there are plenty of these.

Not all is there, we should have support both for variables and function parameters. However, I'm not sure how to extract the assigned variables. Same for the functions and then the function parameter types. Also the global variable should be addressed.

If someone could point out how to get the assigned variables and functions, then I could continue with the rest.

/Martin

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All variables are held in the environment which is a stack of frame objects created here:
https://github.com/jsonata-js/jsonata/blob/master/jsonata.js#L4048
This environment is passed around the variable evaluate functions during expression evaluation.
The frames all link back to a global staticFrame object which contains all the built in functions (note that functions are just variables that bind to function bodies). The frame object contains methods bind and lookup. We might need to add an entries method to list all of the in-scope bindings in order to support what you need.

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Super! That should point me in the right direction. We would also have to deal with scopes and that can be a bit tricky... I'll see what makes sense.

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Closing this issue since I think there is no more work here. Re-open if you disagree.

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