feat[lang]: implement export bundles

[charles-cooper]

What I did

implement exports and export bundles.

export bundles are a way for library authors to group together external functions in the ABI

example:

bundle: IERC_X  # declare a bundle

@internal
def foo() -> uint256:
    return 10

@external
def extern1():
    pass

@external
@Bundle(IERC_X)
def extern2():
    pass

@external
@Bundle(IERC_X, bind=False)  # extern3 ok to export on its own
def extern3():
    pass

@external
@Bundle(IERC_X, bind=True)  # extern4 cannot be exported on its own!
def extern4():
    pass

it can be used like this:

import library

exports: library.IERC_X

@external
def library_foo() -> uint256:
    return library.foo()

or like this:

import library

exports: library.extern1, library.extern2

@external
def library_foo() -> uint256:
    return library.foo()

but not like this(!):

import library

exports: library.extern4  # raises StructureException

@external
def library_foo() -> uint256:
    return library.foo()

How I did it

How to verify it

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[codecov-commenter]

Codecov Report

Attention: 98 lines in your changes are missing coverage. Please review.

Comparison is base (c6f457a) 84.01% compared to head (782659b) 55.74%. Report is 2 commits behind head on master.

Files	Patch %	Lines
vyper/semantics/types/function.py	23.07%	40 Missing :warning:
vyper/semantics/analysis/module.py	12.50%	27 Missing and 1 partial :warning:
vyper/semantics/types/module.py	71.42%	8 Missing and 4 partials :warning:
vyper/ast/nodes.py	38.88%	9 Missing and 2 partials :warning:
vyper/codegen/module.py	80.00%	2 Missing and 1 partial :warning:
vyper/semantics/types/user.py	57.14%	3 Missing :warning:
vyper/semantics/types/base.py	66.66%	1 Missing :warning:

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Additional details and impacted files

@@             Coverage Diff             @@
##           master    #3698       +/-   ##
===========================================
- Coverage   84.01%   55.74%   -28.27%     
===========================================
  Files          92       92               
  Lines       13044    13166      +122     
  Branches     2928     2963       +35     
===========================================
- Hits        10959     7340     -3619     
- Misses       1653     5199     +3546     
- Partials      432      627      +195     

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[fubuloubu]

Would prefer that we create less language keywords so we can namespace better:

from vyper.packaging import Bundle
IERC_X: Bundle  = Bundle() # declare a bundle

@internal
def foo() -> uint256:
    return 10

@external
def extern1():
    pass

@external
@IERC_X.add()
def extern2():
    pass

@external
@IERC_X.add(bind=False)  # extern3 ok to export on its own
def extern3():
    pass

@external
@IERC_X.add(bind=True)  # extern4 cannot be exported on its own!
def extern4():
    pass

[charles-cooper]

Would prefer that we create less language keywords so we can namespace better:

from vyper.packaging import Bundle
IERC_X: Bundle  = Bundle() # declare a bundle

@internal
def foo() -> uint256:
    return 10

@external
def extern1():
    pass

@external
@IERC_X.add()
def extern2():
    pass

@external
@IERC_X.add(bind=False)  # extern3 ok to export on its own
def extern3():
    pass

@external
@IERC_X.add(bind=True)  # extern4 cannot be exported on its own!
def extern4():
    pass

export and bundle are not protected keywords though.

i also don't really like putting Bundle behind a namespace because:

• choosing what to expose in the ABI should be a first class concept in the language
• the proposed syntax looks like it's part of the "standard library" and like you could implement your own export semantics as a decorator. you can't, it's a compiler intrinsic

[fubuloubu]

Well, would say that bundle as a keyword exists in multiple EIPs and would be careful about enshrining its use

[charles-cooper]

I mean we could pick another name. But my point is it's not a keyword, you can still define variables and functions etc named bundle.

[fubuloubu]

I mean we could pick another name. But my point is it's not a keyword, you can still define variables and functions etc named bundle.

I can create a function or state variable named implements too?

[charles-cooper]

I can create a function or state variable named implements too?

yep

[fubuloubu]

I can create a function or state variable named implements too?

yep

So, these two don't conflict?

# interface check
implements: ERC20

# state variable
implements: ERC20

[charles-cooper]

So, these two don't conflict?

# interface check
implements: ERC20

# state variable
implements: ERC20

aha yea they use a similar AST node as for state variable declarations so not those, but everything else -- function names, local variables, names of things

@external
def implements():
    pass

event implements:
    pass

@external
def foo(implements: uint256):
    pass

[charles-cooper]

closing this as superseded (for now) by https://github.com/vyperlang/vyper/pull/3786 and the spec could use some polishing, will revisit in 0.4.1