[ty] Add new diagnosticMode: off

[MichaReiser]

Summary

This PR adds a new diagnosticMode: off, for users that want to use ty's LSP functionality only (go to def, ...) but don't want to see any type errors.

I took the easy way here where the LSP returns an empty response for pull diagnostics rather than changing the registered capabilities. Happy to pursue that if people think it's worth the time.

We may want to add a separate disableSyntaxErrors option for users that want to use ty alongside other Python LSPs. I created a new issue for that.

Closes astral-sh/ty#1755

Test Plan

Added tests

Screen.Recording.2025-12-19.at.11.04.32.mov

[astral-sh-bot]

Diagnostic diff on typing conformance tests

No changes detected when running ty on typing conformance tests ✅

[astral-sh-bot]

mypy_primer results

Changes were detected when running on open source projects

prefect (https://github.com/PrefectHQ/prefect)
- src/integrations/prefect-dbt/prefect_dbt/core/settings.py:94:28: error[invalid-assignment] Object of type `dict[str, Any] | T@resolve_block_document_references` is not assignable to `dict[str, Any]`
+ src/integrations/prefect-dbt/prefect_dbt/core/settings.py:94:28: error[invalid-assignment] Object of type `dict[str, Any] | T@resolve_block_document_references | str | ... omitted 4 union elements` is not assignable to `dict[str, Any]`
- src/integrations/prefect-dbt/prefect_dbt/core/settings.py:99:28: error[invalid-assignment] Object of type `dict[str, Any] | T@resolve_variables` is not assignable to `dict[str, Any]`
+ src/integrations/prefect-dbt/prefect_dbt/core/settings.py:99:28: error[invalid-assignment] Object of type `dict[str, Any] | T@resolve_variables | str | ... omitted 4 union elements` is not assignable to `dict[str, Any]`
- src/prefect/cli/deploy/_core.py:86:21: error[invalid-assignment] Object of type `T@resolve_block_document_references | dict[str, Any]` is not assignable to `dict[str, Any]`
+ src/prefect/cli/deploy/_core.py:86:21: error[invalid-assignment] Object of type `T@resolve_block_document_references | dict[str, Any] | str | ... omitted 4 union elements` is not assignable to `dict[str, Any]`
- src/prefect/cli/deploy/_core.py:87:21: error[invalid-assignment] Object of type `T@resolve_variables` is not assignable to `dict[str, Any]`
+ src/prefect/cli/deploy/_core.py:87:21: error[invalid-assignment] Object of type `T@resolve_variables | str | int | ... omitted 4 union elements` is not assignable to `dict[str, Any]`
- src/prefect/deployments/steps/core.py:137:38: error[invalid-argument-type] Argument is incorrect: Expected `T@resolve_variables`, found `T@resolve_block_document_references | dict[str, Any]`
+ src/prefect/deployments/steps/core.py:137:38: error[invalid-argument-type] Argument is incorrect: Expected `T@resolve_variables`, found `T@resolve_block_document_references | dict[str, Any] | str | ... omitted 4 union elements`
- src/prefect/utilities/templating.py:320:13: error[invalid-assignment] Invalid subscript assignment with key of type `object` and value of type `T@resolve_block_document_references | dict[str, Any]` on object of type `dict[str, Any]`
+ src/prefect/utilities/templating.py:320:13: error[invalid-assignment] Invalid subscript assignment with key of type `object` and value of type `T@resolve_block_document_references | dict[str, Any] | str | ... omitted 4 union elements` on object of type `dict[str, Any]`
- src/prefect/utilities/templating.py:323:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_block_document_references | dict[str, Any]`, found `list[T@resolve_block_document_references | dict[str, Any] | Unknown]`
+ src/prefect/utilities/templating.py:323:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_block_document_references | dict[str, Any]`, found `list[T@resolve_block_document_references | dict[str, Any] | str | ... omitted 5 union elements]`
- src/prefect/utilities/templating.py:437:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_variables`, found `dict[object, T@resolve_variables | Unknown]`
+ src/prefect/utilities/templating.py:437:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_variables`, found `dict[object, T@resolve_variables | str | int | ... omitted 5 union elements]`
- src/prefect/utilities/templating.py:442:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_variables`, found `list[T@resolve_variables | Unknown]`
+ src/prefect/utilities/templating.py:442:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_variables`, found `list[T@resolve_variables | str | int | ... omitted 5 union elements]`
- src/prefect/workers/base.py:228:13: error[invalid-argument-type] Argument is incorrect: Expected `T@resolve_variables`, found `T@resolve_block_document_references | dict[str, Any]`
+ src/prefect/workers/base.py:228:13: error[invalid-argument-type] Argument is incorrect: Expected `T@resolve_variables`, found `T@resolve_block_document_references | dict[str, Any] | str | ... omitted 4 union elements`
- src/prefect/workers/base.py:230:20: error[invalid-argument-type] Argument expression after ** must be a mapping type: Found `T@resolve_variables`
+ src/prefect/workers/base.py:230:20: error[invalid-argument-type] Argument expression after ** must be a mapping type: Found `T@resolve_variables | str | int | ... omitted 4 union elements`

xarray (https://github.com/pydata/xarray)
- xarray/core/dataarray.py:5737:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `T_Xarray@map_blocks | DataArray | Dataset`
+ xarray/core/dataarray.py:5737:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `DataArray | Dataset`
- xarray/core/dataset.py:8866:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `T_Xarray@map_blocks | DataArray | Dataset`
+ xarray/core/dataset.py:8866:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `DataArray | Dataset`

scikit-build-core (https://github.com/scikit-build/scikit-build-core)
- src/scikit_build_core/build/wheel.py:98:20: error[no-matching-overload] No overload of bound method `__init__` matches arguments
- Found 44 diagnostics
+ Found 43 diagnostics

jax (https://github.com/google/jax)
+ jax/_src/tree_util.py:295:31: error[invalid-argument-type] Argument to bound method `register_node` is incorrect: Expected `(Hashable, Iterable[object], /) -> T@register_pytree_node`, found `(_AuxData@register_pytree_node, _Children@register_pytree_node, /) -> T@register_pytree_node`
+ jax/_src/tree_util.py:298:31: error[invalid-argument-type] Argument to bound method `register_node` is incorrect: Expected `(Hashable, Iterable[object], /) -> T@register_pytree_node`, found `(_AuxData@register_pytree_node, _Children@register_pytree_node, /) -> T@register_pytree_node`
+ jax/_src/tree_util.py:301:31: error[invalid-argument-type] Argument to bound method `register_node` is incorrect: Expected `(Hashable, Iterable[object], /) -> T@register_pytree_node`, found `(_AuxData@register_pytree_node, _Children@register_pytree_node, /) -> T@register_pytree_node`
- Found 2799 diagnostics
+ Found 2802 diagnostics

static-frame (https://github.com/static-frame/static-frame)
- static_frame/core/series.py:772:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[Series[Any, Any], TVDtype@Series]`, found `InterGetItemILocReduces[Series[Any, Any] | TypeBlocks | Batch | ... omitted 6 union elements, generic[object]]`
+ static_frame/core/series.py:772:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[Series[Any, Any], TVDtype@Series]`, found `InterGetItemILocReduces[Series[Any, Any] | Top[Index[Any]] | TypeBlocks | ... omitted 6 union elements, generic[object]]`
- static_frame/core/series.py:4072:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[SeriesHE[Any, Any], TVDtype@SeriesHE]`, found `InterGetItemILocReduces[SeriesHE[Any, Any] | TypeBlocks | Batch | ... omitted 7 union elements, generic[object]]`
+ static_frame/core/series.py:4072:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[SeriesHE[Any, Any], TVDtype@SeriesHE]`, found `InterGetItemILocReduces[SeriesHE[Any, Any] | Top[Index[Any]] | TypeBlocks | ... omitted 7 union elements, generic[object]]`

core (https://github.com/home-assistant/core)
+ homeassistant/util/variance.py:47:12: error[invalid-return-type] Return type does not match returned value: expected `(**_P@ignore_variance) -> _R@ignore_variance`, found `_Wrapped[_P@ignore_variance, _R@ignore_variance | int | float | datetime, _P@ignore_variance, _R@ignore_variance | int | float | datetime]`
- Found 14414 diagnostics
+ Found 14415 diagnostics

No memory usage changes detected ✅

[dhruvmanila]

This looks good but I'd prefer the approach to change the capabilities instead (the one that you've mentioned in the description). I'm also fine if you want to do it as a follow-up.

I was wondering if we need to change anything for db.set_check_mode here:

ruff/crates/ty_server/src/session.rs

Lines 550 to 558 in fee4e2d

	if let Some(global_options) = combined_global_options {
	let global_settings = global_options.into_settings();
	if global_settings.diagnostic_mode().is_workspace() {
	for project in self.projects.values_mut() {
	project.db.set_check_mode(CheckMode::AllFiles);
	}
	}
	self.global_settings = Arc::new(global_settings);
	}

but I think it's fine now given that changing the configuration value requires a server restart.

[dhruvmanila]

Is this still required?

[MichaReiser]

Yes, for clients that don't support dynamic registration