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`open` does not open files from a virtual file system

See original GitHub issue

Test file system

__BRYTHON__.add_files({
    "hello.txt": {
        "content": "aGVsbG8gaXMgdGhlIHdheSB0byBnbwo=\n",
        "ctime": 1634418826.57,
        "mtime": 1634418828.0
    }
})

Test code

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <script type="text/javascript" src="brython.js"></script>
  <script type="text/javascript" src="hello.vfs.js"></script>
</head>

<body onload="brython(1)">
<script type="text/python">
hfile = open('hello.txt', 'r')
print(hfile)
hdata = hfile.read()
print(hdata)
</script>
</body>
</html>

And the output in the console is:

Javascript error TypeError: Cannot read properties of undefined (reading 'length')
    at $url_open (py_builtin_functions.js:2993)
    at eval (eval at $B.loop (loaders.js:378), <anonymous>:15:51)
    at Object.$B.loop (loaders.js:378)
    at $B.run_script (py2js.js:12939)
    at Object.$B.loop (loaders.js:398)
    at $B.parser._run_scripts (py2js.js:13133)
    at $B.parser.brython (py2js.js:12878)
    at onload ((index):48)
py_exceptions.js:697 test is js exc is recursion error TypeError: Cannot read properties of undefined (reading 'length')
    at $url_open (py_builtin_functions.js:2993)
    at eval (eval at $B.loop (loaders.js:378), <anonymous>:15:51)
    at Object.$B.loop (loaders.js:378)
    at $B.run_script (py2js.js:12939)
    at Object.$B.loop (loaders.js:398)
    at $B.parser._run_scripts (py2js.js:13133)
    at $B.parser.brython (py2js.js:12878)
    at onload ((index):48) TypeError: Cannot read properties of undefined (reading 'length')
py_exceptions.js:160 print stack ok []
py_utils.js:1106 Traceback (most recent call last):
RuntimeError: TypeError: Cannot read properties of undefined (reading 'length')

The problem, a long guess, seems to be code that wasn’t udpated for a file found in $B.files here: https://github.com/brython-dev/brython/blob/33aeaab551f1b73209326c5a0aecf98642d4c126/www/src/py_builtin_functions.js#L2909-L2919

because the other cases put the result in result.content, which is not happening here

Issue Analytics

State:
Created 2 years ago
Comments:8 (4 by maintainers)

Top GitHub Comments

1reaction

anpylarcommented, Oct 19, 2021

I think the feature is useful. And a small extension would make it more useful

The current logic (simpflied)

Open from $B.files if an entry is available there
if not and the protocol is not file => launch an XMLHttpRequest

As a user I may want to open a file without going to the network. If the file is not available inside $B.files I may want to simply stop there.

For that use case I see two potential implementation options

Extra keyword-argument for open. Something like: _only_local which is a boolean with default value False to avoid altering the current behavior If the file is not in $B.files either None can be returned or an Exception (FileNotFound) be raised
Expose a function which allows testing for the presence of a an entry in $B.files

0reactions

Froggo8311commented, Mar 7, 2022

Maybe add the ability to specify the workings of it- such as if the programmer wanted to set up their own virtual file system, they could provide brython with a custom open class.