IMPR: Type annotations

The codebase currently lacks type hints. Adding type hints would greatly increase the ability for static type checkers like mypy to enforce type-safety and catch bugs at type-checking time.

Adding mypy or an equivalent type checker to pre-commit would help maintain type-safety during the development process.

Operationally, I would suggest adding a type checker like mypy to the pre-commit configuration, but exempting all modules from type checking (because they would all fail).

One by one, modules would be added to mypy's scope, and that module would receive complete type annotations. This should be a safe way to gradually type the entire codebase.

This issue is stale because it has been open for 45 days with no activity.

feat: add mypy type checking to pre-commit

Implemented in DataJoint 2.0

Added mypy type checking with gradual adoption strategy as suggested.

Changes (commit `27391c7`)

pyproject.toml - mypy configuration:

[tool.mypy]
python_version = "3.10"
ignore_missing_imports = true
check_untyped_defs = true

# Modules with complete type coverage - strict checking enabled
[[tool.mypy.overrides]]
module = ["datajoint.content_registry"]
disallow_untyped_defs = true
disallow_incomplete_defs = true
warn_return_any = true

# Modules excluded from type checking until fully typed
[[tool.mypy.overrides]]
module = ["datajoint.admin", "datajoint.autopopulate", ...]  # 28 modules
ignore_errors = true

.pre-commit-config.yaml - mypy hook:

- repo: https://github.com/pre-commit/mirrors-mypy
  rev: v1.14.1
  hooks:
    - id: mypy
      files: ^src/datajoint/
      additional_dependencies:
        - pydantic
        - pydantic-settings
        - types-PyMySQL
        - types-tqdm
        - pandas-stubs
        - numpy

Gradual Adoption Strategy

Now: content_registry.py has strict type checking (100% typed)
Next: Move modules from ignore_errors = true to strict as they're fully typed
Goal: Eventually enable strict checking for all modules

Current Type Coverage

Metric	Status
Functions with return annotations	244 / 527 (46%)
Files with `from __future__ import annotations`	18 / 33 (55%)
Modules with strict mypy	1 / 33
mypy in pre-commit	✅

Developers can now gradually type modules and move them to strict checking.

@d-v-b

@d-v-b Take a look and I will close as completed (as a gradual policy)

feat: add type annotations to errors and hash modules

Type Annotation Coverage Increased

Added type annotations and enabled strict mypy checking for 2 additional modules:

Newly Strict

errors.py - Added type annotation to suggest() method
hash.py - Added type annotations to key_hash() and uuid_from_buffer()

Current Status

3 modules now under strict mypy checking:

content_registry ✓
errors ✓ (new)
hash ✓ (new)

26 modules remain in gradual adoption queue

Next Steps

Following the gradual adoption strategy, additional modules can be promoted to strict checking as they receive complete type annotations. The infrastructure is in place - modules can be moved from the excluded list to the strict list as they're typed.

Commit: feat: add type annotations to errors and hash modules

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IMPR: Type annotations #1266

Implemented in DataJoint 2.0

Changes (commit `27391c7`)

Gradual Adoption Strategy

Current Type Coverage

Type Annotation Coverage Increased

Newly Strict

Current Status

Next Steps

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IMPR: Type annotations #1266

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github-actions commented on Oct 13, 2025

dimitri-yatsenko commented on Jan 8, 2026

Implemented in DataJoint 2.0

Changes (commit 27391c7)

Gradual Adoption Strategy

Current Type Coverage

dimitri-yatsenko commented on Jan 8, 2026

dimitri-yatsenko commented on Jan 8, 2026

Type Annotation Coverage Increased

Newly Strict

Current Status

Next Steps

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions

Changes (commit `27391c7`)