Language Server incorrectly marks variables as undefined in nested list comprehensions

[DonJayamanne]

From @mawright on November 11, 2018 3:38

Environment data

• VS Code version: 1.28.2
• Extension version (available under the Extensions sidebar): 2018.10.1
• OS and version: Ubuntu 16.04
• Python version (& distribution if applicable, e.g. Anaconda): Anaconda 3.6.6
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): conda
• Relevant/affected Python packages and their versions: N/A

Actual behavior

Expected behavior

Linter does not incorrectly mark variable as undeclared

Steps to reproduce:

1. See screenshot

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.
Microsoft Python Language Server version 0.1.60.0
Initializing for /home/matt/anaconda3/envs/learn/bin/python

Output from Console under the Developer Tools panel (toggle Developer Tools on under Help)

/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:1409  INFO no standard startup: not a new window
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:4274 Overwriting grammar scope name to file mapping for scope source.python.
Old grammar file: file:///usr/share/code/resources/app/extensions/python/syntaxes/MagicPython.tmLanguage.json.
New grammar file: file:///home/matt/.vscode/extensions/magicstack.magicpython-1.1.0/grammars/MagicPython.tmLanguage
e.register @ /usr/share/code/resources/app/out/vs/workbench/workbench.main.js:4274
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] vscode-icons is active!
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Display locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Notify locators are locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Detected refreshing of Interpreters, Arg 1: {}, Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Display locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Notify locators are locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Detected refreshing of Interpreters, Arg 1: {}, Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Display locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Notify locators are locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Detected refreshing of Interpreters, Arg 1: {}, Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Display locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Notify locators are locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Detected refreshing of Interpreters, Arg 1: {}, Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Create file systemwatcher with pattern */python
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Create file systemwatcher with pattern */*/python
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Display locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Notify locators are locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Detected refreshing of Interpreters, Arg 1: {}, Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Display locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Notify locators are locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Detected refreshing of Interpreters, Arg 1: {}, Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Display locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Notify locators are locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Detected refreshing of Interpreters, Arg 1: {}, Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Register Intepreter Watcher, Arg 1: undefined, Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Build the workspace interpreter watcher, Arg 1: undefined, Return Value: UNABLE TO DETERMINE VALUE
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Get language server folder name, , Return Value: "languageServer.0.1.60"
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Git extension API method 'getGitPath' is deprecated.
t.log @ /usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Hide locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: All locators have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Hide locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: All locators have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Hide locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: All locators have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Hide locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: All locators have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Hide locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: All locators have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Hide locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: All locators have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Hide locator refreshing progress, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: All locators have completed locating, , Return Value: 
/usr/share/code/resources/app/out/vs/workbench/workbench.main.js:282 [Extension Host] Python Extension: Checking whether locactors have completed locating, , Return Value: 

Copied from original issue: microsoft/vscode-python#3297

[DonJayamanne]

From @darrickyee on November 11, 2018 14:54

I think this is a language server issue, not a linting issue. The message is not prefixed with [pylint] and still appears when pylint is disabled.