Support for dict unpacking (object spread equivalent)

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
deno, javascript, python
Domain
compilers

Research direction

Start with the testme.py examples in the issue and reproduce both the Python result and the Transcrypt compilation failure, then inspect the compiler entry point used by transcrypt. Verify that dict unpacking compiles and that the generated JavaScript produces {'a': 1, 'b': 2} when run with Deno.

Written by the indexing model from the issue text.

Description

IS: enhancement PRIO: 3 nice

It would be nice to support dict unpacking {**a, "b": 2}, the Python equivalent to JavaScript object spread { ...a, b: 2}.

# testme.py
a = {"a": 1}
b = {**a, "b": 2}
print(b)

% python testme.py 
{'a': 1, 'b': 2}
% transcrypt testme.py        

Transcrypt (TM) Python to JavaScript Small Sane Subset Transpiler Version 3.9.0
Copyright (C) Geatec Engineering. License: Apache 2.0


Saving target code in: ./__target__/org.transcrypt.__runtime__.js
Saving minified target code in: ./__target__/org.transcrypt.__runtime__.js

Error while compiling (offending file last):
        File 'testme', line 3, namely:

        Error while compiling (offending file last):
        File 'testme', line 3, namely:


Aborted

Using dict with kw args compiles but doesn't work:

# testme.py
a = {"a": 1}
b = dict(**a, **{"b": 2})
print(b)

% python testme.py 
{'a': 1, 'b': 2}
% transcrypt testme.py 

Transcrypt (TM) Python to JavaScript Small Sane Subset Transpiler Version 3.9.0
Copyright (C) Geatec Engineering. License: Apache 2.0



Ready

% deno run __target__/testme.js
error: Uncaught ReferenceError: adict is not defined
    at file://./__target__/testme.js:3:316
Dominant language
Python
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