add type hints

[jicruz96]

closes #41

Changes

• Type hints added to all declarations.
• loaded data is typed in geonamescache.types using typing.TypedDict
• typing-extensions added as package dependency to ensure type hints work for all Python versions >=3.6*

This will offer a more user-friendly experience in IDEs, including auto-complete and type checking (if the user has configured these).

Notes

*If you do not want any dependencies added to the package, I can provide an alternate PR

That alternate PR would use sys.version_info to check the python version before assigning types, and then use only the typing features available for each respective python version. I would ensure to support up to 3.8, and can support up to 3.6 if requested.

---

On formatting:

There was no formatting or linting config beyond the .editorconfig, so I took my best guess with line breaks and line lengths.

[yaph]

Thanks for your contribution! I'll review and test the changes in the beginning of next week. No worries about the workflow fail. I may replace the current workflow anyway before a new release.

[yaph]

I reviewed the code and it looks good to me. Thanks for your effort so far! The tests are running, but a mypy check returned some errors. Would you look into these?

$ mypy --install-types --non-interactive geonamescache tests

geonamescache/__init__.py:40: error: Incompatible types in assignment (expression has type "dict[str, Any]", variable has type "dict[Literal['AF', 'AN', 'AS', 'EU', 'NA', 'OC', 'SA'], Continent] | None")  [assignment]
geonamescache/__init__.py:42: error: Incompatible return value type (got "dict[Literal['AF', 'AN', 'AS', 'EU', 'NA', 'OC', 'SA'], Continent] | None", expected "dict[Literal['AF', 'AN', 'AS', 'EU', 'NA', 'OC', 'SA'], Continent]")  [return-value]
geonamescache/__init__.py:56: error: Incompatible return value type (got "dict[str, USState]", expected "dict[Literal['Alaska', 'Alabama', 'Arkansas', 'Arizona', 'California', 'Colorado', 'Connecticut', 'District of Columbia', 'Delaware', 'Florida', 'Georgia', 'Hawaii', 'Iowa', 'Idaho', 'Illinois', 'Indiana', 'Kansas', 'Kentucky', 'Louisiana', 'Massachusetts', 'Maryland', 'Maine', 'Michigan', 'Minnesota', 'Missouri', 'Mississippi', 'Montana', 'North Carolina', 'North Dakota', 'Nebraska', 'New Hampshire', 'New Jersey', 'New Mexico', 'Nevada', 'New York', 'Ohio', 'Oklahoma', 'Oregon', 'Pennsylvania', 'Rhode Island', 'South Carolina', 'South Dakota', 'Tennessee', 'Texas', 'Utah', 'Virginia', 'Vermont', 'Washington', 'Wisconsin', 'West Virginia', 'Wyoming'], USState]")  [return-value]
geonamescache/__init__.py:56: error: Argument 1 to "get_dataset_by_key" of "GeonamesCache" has incompatible type "dict[Literal['AK', 'AL', 'AR', 'AZ', 'CA', 'CO', 'CT', 'DC', 'DE', 'FL', 'GA', 'HI', 'IA', 'ID', 'IL', 'IN', 'KS', 'KY', 'LA', 'MA', 'MD', 'ME', 'MI', 'MN', 'MO', 'MS', 'MT', 'NC', 'ND', 'NE', 'NH', 'NJ', 'NM', 'NV', 'NY', 'OH', 'OK', 'OR', 'PA', 'RI', 'SC', 'SD', 'TN', 'TX', 'UT', 'VA', 'VT', 'WA', 'WI', 'WV', 'WY'], USState]"; expected "dict[str, USState]"  [arg-type]
geonamescache/mappers.py:27: error: Missing return statement  [return]
geonamescache/mappers.py:34: error: TypedDict key must be a string literal; expected one of ("areakm2", "capital", "continentcode", "currencycode", "currencyname", ...)  [literal-required]
Found 6 errors in 2 files (checked 9 source files)

[jicruz96]

I reviewed the code and it looks good to me. Thanks for your effort so far! The tests are running, but a mypy check returned some errors. Would you look into these?

@yaph I've handled the remaining mypy errors by loosening the type hints a bit for the helpers in 01e8341 and by defining specific function overloads for geonamescache.mappers.country in commits d0cc123 and 89ae766 (edit, also commit 89ae766)

mypy --install-types --non-interactive geonamescache 
Success: no issues found in 5 source files

The new function overloads also make the usage of country() much better at type-inference and type checks too:

[jicruz96]

Thanks for your contribution! I'll review and test the changes in the beginning of next week. No worries about the workflow fail. I may replace the current workflow anyway before a new release.

Sounds good! fwiw I would expect that adding a pip install -e . to your github workflow file should fix the currently broken tests if you choose not to replace the existing workflow

[yaph]

Thanks so much for your work @jicruz96! While there are no breaking changes for the end user, I'll create a new major release soon.