What causes Pyright to run out of memory?

[qexat]

Pyright crashes (runs out of memory) after ~30 seconds on this file: https://pastebin.com/qfmff5ep
Happens inside Visual Studio Code (Pylance), but also with the CLI including the --watch option.

What does this code have in particular that leads to that?

Configuration

Python 3.12.4, Pyright 1.1.374

"python.analysis.autoImportCompletions": true,
  "python.analysis.diagnosticSeverityOverrides": {
    "reportAssertAlwaysTrue": "warning",
    "reportConstantRedefinition": "error",
    "reportGeneralTypeIssues": "error",
    "reportImportCycles": "error",
    "reportInconsistentConstructor": "error",
    "reportInvalidStringEscapeSequence": "error",
    "reportMatchNotExhaustive": "warning",
    "reportMissingImports": "error",
    "reportMissingParameterType": "error",
    "reportOptionalCall": "error",
    "reportOptionalContextManager": "error",
    "reportOptionalIterable": "error",
    "reportOptionalMemberAccess": "error",
    "reportOptionalSubscript": "error",
    "reportPrivateUsage": "error",
    "reportSelfClsParameterName": "warning",
    "reportUnboundVariable": "error",
    "reportUndefinedVariable": "error",
    "reportUninitializedInstanceVariable": "error",
    "reportUnknownArgumentType": "error",
    "reportUnknownMemberType": "error",
    "reportUnknownParameterType": "error",
    "reportUnknownVariableType": "error",
    "reportUnnecessaryComparison": "information",
    "reportUnnecessaryContains": "information",
    "reportUnnecessaryTypeIgnoreComment": "information",
    "reportUntypedBaseClass": "error",
    "reportUntypedClassDecorator": "error",
    "reportUntypedFunctionDecorator": "error",
    "reportUntypedNamedTuple": "error",
    "reportUnusedCallResult": "information",
    "reportUnusedFunction": "warning",
    "reportUnusedClass": "warning",
    "reportUnusedExpression": "error",
    "reportUnusedImport": "warning",
    "reportUnusedVariable": "error",
  },
  "python.analysis.exclude": [
    ".venv/**"
  ],
  "python.analysis.typeCheckingMode": "strict",
  "python.analysis.autoFormatStrings": true,

Crash log

pyright-crash-log.txt

Related discussions/issues

#4941: does not apply: my configuration has been excluding my virtual environment from analysis for a while
#8241: does not apply: I tried on v1.1.368 and it causes the same issue

[qexat]

Note: Tried to run pyright with NODE_OPTIONS=--max-old-space-size=4096 but the issue still occurs.

[qexat]

Are you able to repro the problem if you direct pyright to type check only that file (i.e. run pyright <name_of_file.py>)?

Yes, in fact I haven't tried with checking on the whole folder.

When I run:

pyright --verbose kisp/middleend/types.py >log.txt 2>&1

Here are the logs I get:

Loading pyproject.toml file at /home/clarisse/Code/Repositories/pykisp/pyproject.toml
Pyproject file "/home/clarisse/Code/Repositories/pykisp/pyproject.toml" has no "[tool.pyright]" section.
No include entries specified; assuming /home/clarisse/Code/Repositories/pykisp
Auto-excluding **/node_modules
Auto-excluding **/__pycache__
Auto-excluding **/.*
Search paths for file:///home/clarisse/Code/Repositories/pykisp
  /usr/lib/node_modules/pyright/dist/typeshed-fallback/stdlib
  /home/clarisse/Code/Repositories/pykisp
  /home/clarisse/Code/Repositories/pykisp/typings
  /usr/lib/node_modules/pyright/dist/typeshed-fallback/stubs/...
  /usr/lib/python3.12
  /usr/lib/python3.12/lib-dynload
  /home/clarisse/Code/Repositories/pykisp/.venv/lib/python3.12/site-packages
Found 1 source file

<--- Last few GCs --->

[50296:0x5a0ff735c000]    23526 ms: Mark-Compact 1964.5 (2086.9) -> 1949.7 (2086.9) MB, pooled: 1 MB, 795.30 / 0.00 ms  (average mu = 0.098, current mu = 0.036) allocation failure; scavenge might not succeed
[50296:0x5a0ff735c000]    24356 ms: Mark-Compact 1965.7 (2087.2) -> 1950.9 (2088.2) MB, pooled: 0 MB, 808.64 / 0.00 ms  (average mu = 0.063, current mu = 0.026) allocation failure; scavenge might not succeed


<--- JS stacktrace --->

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory
----- Native stack trace -----

 1: 0x5a0fe396647d node::OOMErrorHandler(char const*, v8::OOMDetails const&) [node]
 2: 0x5a0fe3e0e244 v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, v8::OOMDetails const&) [node]
 3: 0x5a0fe3e0e619 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, v8::OOMDetails const&) [node]
 4: 0x5a0fe4038c0c  [node]
 5: 0x5a0fe4038c34  [node]
 6: 0x5a0fe405159e  [node]
 7: 0x5a0fe405436c  [node]
 8: 0x5a0fe49dcb37  [node]

There is no symlink except for the ones that are always present in the virtual environment folder (i.e. generated by virtualenv, such as the python binary).

[erictraut]

Without the ability to repro what you're seeing, I'll need you to do additional diagnostic steps.

Here are some additional things you might want to investigate:

1. What version of node do you have installed on your machine? Execute node -v in the shell. If it's really old (<18), try upgrading.
2. Try to repro with a fresh venv that has nothing but attrs installed.
3. Try commenting out parts of the file (using bisection) to identify the specific function or sub-function that results in the problem.

[qexat]

1. node -v outputs v22.5.1.

$ echo $VIRTUAL_ENV
/home/clarisse/Code/Repositories/pykisp/.venv-repro

$ python -m pip freeze
attrs==24.2.0

Loading pyproject.toml file at /home/clarisse/Code/Repositories/pykisp/pyproject.toml
Pyproject file "/home/clarisse/Code/Repositories/pykisp/pyproject.toml" has no "[tool.pyright]" section.
No include entries specified; assuming /home/clarisse/Code/Repositories/pykisp
Auto-excluding **/node_modules
Auto-excluding **/__pycache__
Auto-excluding **/.*
Search paths for file:///home/clarisse/Code/Repositories/pykisp
  /usr/lib/node_modules/pyright/dist/typeshed-fallback/stdlib
  /home/clarisse/Code/Repositories/pykisp
  /home/clarisse/Code/Repositories/pykisp/typings
  /usr/lib/node_modules/pyright/dist/typeshed-fallback/stubs/...
  /usr/lib/python3.12
  /usr/lib/python3.12/lib-dynload
  /home/clarisse/Code/Repositories/pykisp/.venv-repro/lib/python3.12/site-packages
Found 1 source file

<--- Last few GCs --->

[51578:0x5ee91dad0000]    25400 ms: Scavenge (interleaved) 2039.4 (2079.4) -> 2035.9 (2087.7) MB, pooled: 0 MB, 5.70 / 0.00 ms  (average mu = 0.244, current mu = 0.223) allocation failure; 
[51578:0x5ee91dad0000]    26272 ms: Mark-Compact (reduce) 2036.2 (2087.7) -> 2035.9 (2072.9) MB, pooled: 0 MB, 762.46 / 0.00 ms  (+ 11.0 ms in 0 steps since start of marking, biggest step 0.0 ms, walltime since start of marking 782 ms) (average mu = 0.240

<--- JS stacktrace --->

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory
----- Native stack trace -----

 1: 0x5ee91256647d node::OOMErrorHandler(char const*, v8::OOMDetails const&) [node]
 2: 0x5ee912a0e244 v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, v8::OOMDetails const&) [node]
 3: 0x5ee912a0e619 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, v8::OOMDetails const&) [node]
 4: 0x5ee912c38c0c  [node]
 5: 0x5ee912c38c34  [node]
 6: 0x5ee912c5159e  [node]
 7: 0x5ee912c5436c  [node]
 8: 0x5ee9135dcb37  [node]

3. It seems that Pyright does not go OoM if I comment out all the lines that perform a recursive call in is_equivalence methods of both ProductType and SumType classes (this does not seem to hold for other classes). Put in another way, this is the minimal version for which Pyright does not crash (and completes in ~0.878s): https://pastebin.com/GrijwMWZ

For transparency, this version has minor changes compared to the original comment's one: TypeVariable was renamed MetaVariable and there is additional commented code. It does not affect any of the outcomes.

[erictraut]

Thanks for the additional details. I was able to repro the problem on my system, and I have a fix that will be included in the next release of pyright.

[qexat]

Thank you for the quick fix!
Should this discussion be converted to an issue?