Run Selection/Line in Python Terminal - SyntaxError

[DougPlumley]

Environment data

• VS Code version: 1.35.1
• Extension version (available under the Extensions sidebar): 2019.6.22090
• OS and version: macOS Mojave 10.14.4
• Python version (& distribution if applicable, e.g. Anaconda): Python 3.7.3
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): N/A
• Relevant/affected Python packages and their versions: N/A
• Jedi or Language Server? (i.e. what is "python.jediEnabled" set to; more info How to update the language server to the latest stable version #3977): Microsoft Python Language Server version 0.3.20.0

Expected behaviour

The following code should run as expected when executed using "Run Selection/Line in Python Terminal".

{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}
{
    "test": "test",
    "test2": "test2"
}

Actual behaviour

Approximately 1/5 of the time on my machine it will result in a syntax error. I've noticed this becomes more of an issue the longer my selection is. For example I can't reproduce the error using the above code when I only have lines 1 - 88 selected (989 total characters). When I select 1 - 92 (1035 total characters) the issue starts occurring. Note that characters in the Python terminal start to be transposed which may suggest there's some sort of race condition as data from the source is inserted into the terminal.

>>> 
>>> {
...     "test": "test",
...     "test2": "test2"
... }
{'test': 'test', 'test2': 'test2'}
>>> 
>>> {
...     "test":     "test":     "t": "test2"
  File "<stdin>", line 2
    "test":     "test":     "t": "test2"
                      ^
SyntaxError: invalid syntax
>>> }
  File "<stdin>", line 1
    }
    ^
SyntaxError: invalid syntax

Steps to reproduce:

1. Copy example code into source file
2. Select lines 1 - 92
3. Run selection repeatedly until error occurrs

Logs

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

Starting Microsoft Python language server.
[Info  - 4:55:56 PM] Analysis cache path: /Users/dplumley/Library/Caches/Microsoft/Python Language Server
[Info  - 4:55:56 PM] GetCurrentSearchPaths /usr/local/bin/python3 
[Info  - 4:55:57 PM] Interpreter search paths:
[Info  - 4:55:57 PM]     /private/var/folders/h1/gp3rgbx518zcprwky90s5y_80000gp/T/egh4vhvx.wqq
[Info  - 4:55:57 PM]     /usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7
[Info  - 4:55:57 PM]     /usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/lib-dynload
[Info  - 4:55:57 PM]     /usr/local/lib/python3.7/site-packages
[Info  - 4:55:57 PM] User search paths:
[Info  - 4:55:57 PM] Microsoft Python Language Server version 0.3.20.0
[Info  - 4:55:57 PM] Initializing for /usr/local/bin/python3

Output from Console under the Developer Tools panel (toggle Developer Tools on under Help; turn on source maps to make any tracebacks be useful by running Enable source map support for extension debugging)

[Extension Host] Info Python Extension: 2019-06-25 16:58:20: Cached data exists getEnvironmentVariables, <No Resource>
workbench.main.js:238 [Extension Host] Info Python Extension: 2019-06-25 16:58:22: Cached data exists getEnvironmentVariables, <No Resource>

[DougPlumley]

I'll also mention that this seems to start occurring after I select 1024+ characters which is an interesting number to start to see an issue at.

Example:

{
    "test": "test",
    "test2": "test",
    "test3": "test",
    "test4": "test",
    "test5": "test",
    "test6": "test",
    "test7": "test",
    "test8": "test",
    "test9": "test"
}
{
    "test": "test",
    "test2": "test",
    "test3": "test",
    "test4": "test",
    "test5": "test",
    "test6": "test",
    "test7": "test",
    "test8": "test",
    "test9": "test"
}
{
    "test": "test",
    "test2": "test",
    "test3": "test",
    "test4": "test",
    "test5": "test",
    "test6": "test",
    "test7": "test",
    "test8": "test",
    "test9": "test"
}
{
    "test": "test",
    "test2": "test",
    "test3": "test",
    "test4": "test",
    "test5": "test",
    "test6": "test",
    "test7": "test",
    "test8": "test",
    "test9": "test"
}
{
    "test": "test",
    "test2": "test",
    "test3": "test",
    "test4": "test",
    "test5": "test",
    "test6": "test",
    "test7": "test",
    "test8": "test",
    "test9": "test",
    "test9": "test",
    "test9": "test",
    "test9": "test1234",
}

[ericsnowcurrently]

This is a known upstream issue: microsoft/vscode#38137. It is possible that we could temporarily work around the problem in the Python extension (e.g. chunk the data sent to the terminal), but I'm not sure. We'll look into it.

[DougPlumley]

Thanks @ericsnowcurrently !

[luabud]

Closing in favour of microsoft/vscode#38137.