🦺 Validate priority (#14)

### TL;DR

This PR adds priority field validation for SiteMapUrl in the sitemapr module, including corresponding exception handling and tests for invalid values.

### What changed?

- Added `SiteMaprException` and `InvalidSiteMapPriority` in `sitemapr.exceptions`.
- Added priority validation in `SiteMapUrl` model (with corresponding validator).
- Added unit tests for the newly added validation logic in `tests/test_core.py`.
- .gitignore now tracks the .python-version file.

### How to test?

- Run `pytest` to ensure all test cases, especially the new ones for priority validation, pass successfully.

### Why make this change?

- Adding priority validation ensures that the priority values are within the acceptable range (0.0 to 1.0), thus maintaining data integrity.

.gitignore

@@ -85,7 +85,7 @@ ipython_config.py
 # pyenv
 #   For a library or package, you might want to ignore these files since the code is
 #   intended to run in multiple environments; otherwise, check them in:
-# .python-version
+.python-version
 
 # pipenv
 #   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.

sitemapr/models.py

@@ -1,7 +1,8 @@
 from collections.abc import Callable
+from decimal import Decimal
 from typing import Literal, TypeVar
 
-from pydantic import BaseModel
+from pydantic import BaseModel, ValidationError, validator
 
 T = TypeVar("T")
 
@@ -30,3 +31,19 @@ class SiteMapUrl(BaseModel):
     lastmod: str | None = None
     changefreq: ChangeFreq | None = None  # Google ignores this
     priority: str | None = None  # Google ignores this
+
+    @validator("priority")
+    def validate_priority(cls, v: str | None) -> str | None:
+        if v is None:
+            return v
+        try:
+            priority = Decimal(v)
+        except Exception as e:
+            raise ValidationError(
+                "Priority must be a valid decimal string between 0.0 and 1.0"
+            ) from e
+
+        if 0 <= priority <= 1:
+            return f"{priority:.1f}"
+
+        raise ValidationError("Priority must be between 0.0 and 1.0")

tests/test_core.py

@@ -1,5 +1,8 @@
 import pathlib
 
+import pytest
+from pydantic import ValidationError
+
 from sitemapr import Page, Param, SiteMapr, SiteMapUrl
 
 
@@ -168,6 +171,29 @@ def test_iter_url_works():
     assert actuals == expected
 
 
+def test_iter_url_raises_error_when_priority_is_invalid():
+    """iter_url should raise an error when priority is invalid."""
+    # given
+    invalid_priority = "1.1"
+
+    base_url = "https://example.com"
+    pages = [
+        Page(
+            path="",
+            query_params=[
+                Param(name="page", values=["home", "about", "contact"]),
+                Param(name="sort", values=["asc", "desc"]),
+            ],
+            priority=invalid_priority,
+        ),
+    ]
+    sitemapr = SiteMapr(base_url=base_url, pages=pages)
+
+    # when, then
+    with pytest.raises(ValidationError):
+        list(sitemapr.iter_urls())
+
+
 def test_save_works(tmp_path: pathlib.Path):
     """save should save sitemap.xml when there is only one page."""
     # given