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author | Damien George <damien@micropython.org> | 2024-06-24 13:03:44 +1000 |
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committer | Damien George <damien@micropython.org> | 2024-06-28 11:40:24 +1000 |
commit | 95c19e05ffd204f8f375b6e04e4ae45770ec0dbc (patch) | |
tree | d95ec6d7fa695d85527015699b3c7dff2b0ae260 /docs/esp8266/tutorial/filesystem.rst | |
parent | 5dff78f38edc0354e854e6c73af61c5064afe9d3 (diff) | |
download | micropython-95c19e05ffd204f8f375b6e04e4ae45770ec0dbc.tar.gz micropython-95c19e05ffd204f8f375b6e04e4ae45770ec0dbc.zip |
webassembly/objjsproxy: Lookup attributes without testing they exist.
In JavaScript when accessing an attribute such as `obj.attr` a value of
`undefined` is returned if the attribute does not exist. This is unlike
Python semantics where an `AttributeError` is raised. Furthermore, in some
cases in JavaScript (eg a Proxy instance) `attr in obj` can return false
yet `obj.attr` is still valid and returns something other than `undefined`.
So the source of truth for whether a JavaScript attribute exists is to just
right away attempt `obj.attr`.
To more closely match these JavaScript semantics when proxying a JavaScript
object through to Python, change the attribute lookup logic on a `JsProxy`
so that it immediately attempts `obj.attr` instead of first testing if the
attribute exists via `attr in obj`.
This allows JavaScript objects which dynamically create attributes to work
correctly on the Python side, with both `obj.attr` and `obj["attr"]`. Note
that `obj["attr"]` already works in all cases because it immediately does
the subscript access without first testing if the attribute exists.
As a benefit, this new behaviour matches the Pyodide behaviour.
Signed-off-by: Damien George <damien@micropython.org>
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