Implement parser for mapping key lookup (e.g. `m[0][1]`) #3943

gnidan · 2021-03-23T04:14:02Z

Addresses #3877

Had this lying around from when I discovered parjs a few weeks ago. Decided to clean it up as a draft for review, in case it's something we can utilize in @truffle/decoder.

As it stands, this PR adds a new package @truffle/parse-mapping-lookup, whose name is terrible and needs to change. This new package exposes a function parse(), to accept a struct/mapping lookup expression (m[0], ledger.balances[0], etc.) and return an AST representation of that expression.

This handles literal floating point numbers and strings, but it doesn't do anything special with those values. It does handle escape sequences (thanks to parjs's own example). It currently loses information, in that m["0x"] will parse the same as m["\"0x\""]. @haltman-at I figure this is something that would be handled by @truffle/encoder, if we want it, so I didn't get fancy.

This also squashes all possibly useful error handling; that will likely be something to improve even slightly before merging.

See test cases for an overview of supported syntax.

Possibly minor note: I borrowed the original tsconfig for this new package from @truffle/db, so it uses src/, not lib/). This was because it seemed to be the fastest way to get jest working for tests, but we might want to update this to borrow from one of the codec packages instead.

haltman-at

OK, I think my biggest comment is that I think we should distinguish string literals from other literals. But see below for more detailed comments.

I guess some of these comments are like "is this supposed to be Solidity or JS", and I guess the answer is Solidity, so, uh, I guess it's the Solidity branch of those conditionals that you want to take. :P

packages/parse-mapping-lookup/package.json

packages/parse-mapping-lookup/src/parser.ts

haltman-at · 2021-04-20T21:50:58Z

packages/parse-mapping-lookup/src/parser.ts

+  export const stringP = stringEntriesP.pipe(many(), stringify(), between('"'));
+}
+
+const numberP = int().pipe(or(float()));


I guess you're relying on builtins here? You may want to make sure these actually matches Solidity's numeric literal syntax, which for instance allows underscores (no more than one consecutively) between digits for grouping purposes.

Edit: Removed comment about JS numeric literals since those aren't relevant

packages/parse-mapping-lookup/src/ast.ts

haltman-at · 2021-04-20T22:12:36Z

packages/parse-mapping-lookup/src/parser.ts

+
+const stringP = Strings.stringP;
+
+const literalP = numberP.pipe(


Solidity has other sorts of literals that I think need to be accounted for. Specifically:

Boolean literals (true and false)

Hex string literals -- I assume static bytestring literals 0x1234 (and address literals) fall under numeric literals, but there's also dynamic bytestring / hex string literals hex"deadbeef". (Edit: This also has a single-quoted form.)

It also might be worth supporting Solidity units here, as those are effectively part of numeric literals?

Oops, one more I forgot about -- string literals are normally restricted to ASCII, but you can also do unicode string literals as unicode"..."; better account for that too.

Boolean literals

hex"deadbeef" literals

~~unicode"..." literals~~

Solidity units ( gwei, etc.)

Hm so unicode literals are a bit annoying, it seems, because Parjs seems to just assume its input is in the BMP (See their README section Parsing Unicode).

It should be doable to restrict "" literals to ASCII, but it might be a bit annoying to write the parser for that?

What do you think of this:

Exclude unicode"..." as unsupported for now (since BMP restriction suggests that we shouldn't make the promise of full-unicode support)

Don't restrict "" to ASCII in the meantime, to afford some way of specifying literals that include BMP characters.

Alternatively, if you want to be a stickler about "" meaning ASCII, we could just define our own literal bmp"" to be more explicit.

Thoughts?

I don't think we need to actually enforce the ASCII restriction. Especially as that's relatively recent, older Solidity doesn't make a distinction.

I think it's also OK to exclude unicode"..." for now. Proper Unicode handling will be a pain regardless of how we do it, so maybe it's OK if we just don't support it all properly for now. (Especially the \xNN escape codes...)

(Especially the \xNN escape codes...)

I don't want to know 😅

Too bad I'm going to explain anyway! :P In Solidity, you can do "\xNN" to insert a particular byte. Note, not a particular character -- a particular byte, regardless of whether or not this makes valid UTF-8. However, if it's invalid UTF-8, then you won't be able to use it as a string, only as a bytes or bytesN (since string literals can be used as either). So, e.g., unicode"\xA1" is not the same as unicode"\u00A1" or unicode"¡", but rather is the same as hex"A1", and so is an error if used as a string rather than a bytes/bytesN.

Ha! Does the Solidity compiler catch this up-front? Or is it a runtime problem?

Too bad I'm going to explain anyway!

Good cause I was lying.

The Solidity compiler detects it upfront. It is possible to put bad UTF-8 inside a string at runtime; there are no runtime checks on whether your UTF-8 is good. But attempting to do so directly from a literal (whether unicode or hex or whatever) will trip the compile-time check and cause a compile error. If you really want to put bad UTF-8 inside a string, you'll need to be sneakier about it. (Putting it in a bytes and the converting that bytes to a string will do the trick. :) )

packages/parse-mapping-lookup/src/ast.ts

- Ensure Literal interface includes `type` field as discriminator - Add some generics infrasturcture for building AST constructors - Add support for boolean literals

- Define custom type names for each form kind in the AST - Update tests to look for one-of `{ trace, value }`

gnidan requested a review from haltman-at March 23, 2021 04:14

haltman-at reviewed Apr 20, 2021

View reviewed changes

gnidan force-pushed the decoder/parjs branch from c44a70d to 24bf8cf Compare April 23, 2021 23:27

gnidan mentioned this pull request Apr 24, 2021

Not all packages' package.json files include repository field + directory #3998

Closed

gnidan force-pushed the decoder/parjs branch 2 times, most recently from 540659d to c4d40de Compare April 24, 2021 04:56

g. nicholas d'andrea added 16 commits April 28, 2021 21:10

Add initial parser

b77f763

Handle _ and $

3b7e98c

Use more explicit names than Access and Lookup

003641d

Expand support for different kinds of literals

8a6588f

- Ensure Literal interface includes `type` field as discriminator - Add some generics infrasturcture for building AST constructors - Add support for boolean literals

Handle Solidity escape sequences

0de4885

Add support for hex literals

9bd698b

[squashme] Simplify LiteralGenerics a bit

a11b8f1

[squashme] Separate it() blocks for erroroneous expressions

01198c9

Add support for enum literals

ffee516

Upgrade prettier to ^2.2.1

a2db4bd

Add eslintrc for package

90e7d63

Reduce complexity of literals

c743bc6

Simultaneously define parsers and AST

e47bc35

Remove Literal prefix

a7f6ce7

Improve reporting for parse errors

b25bbd7

- Define custom type names for each form kind in the AST - Update tests to look for one-of `{ trace, value }`

Prevent empty index access ([])

f8966ac

gnidan force-pushed the decoder/parjs branch from a1a6f35 to f8966ac Compare April 30, 2021 23:28

gnidan changed the base branch from develop to wrap April 30, 2021 23:31

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Implement parser for mapping key lookup (e.g. `m[0][1]`) #3943

Implement parser for mapping key lookup (e.g. `m[0][1]`) #3943

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		const stringP = Strings.stringP;

		const literalP = numberP.pipe(

Implement parser for mapping key lookup (e.g. m[0][1]) #3943

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Implement parser for mapping key lookup (e.g. m[0][1]) #3943

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Implement parser for mapping key lookup (e.g. `m[0][1]`) #3943

Implement parser for mapping key lookup (e.g. `m[0][1]`) #3943

gnidan commented Mar 23, 2021 •

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