feat: Adds vega-themes.json using vl_convert (#3523)

* feat: Adds `vega-themes.json` using `vl_convert`

#3519 (comment)

* Update vega-themes.json

* fix: Force LF

* fix: Use `sort_keys` for deterministic `vega-themes.json`

* build: run `generate-schema-wrapper`

* ci: Introduce `vl_convert` dependency to GH `Test that schema generation has no effect`

#3519 (comment)

https://github.com/vega/altair/actions/runs/10263632193/job/28395892206?pr=3523

* ci: Output diff when schema generation has an effect

Not sure of the right command here, as I can't repro locally

* ci: Change gitattributes to always LF

* fix: re-run with fresh env

#3523 (comment)

* feat(typing): Generate `VegaThemes` alias

Resolves the *long-term* solution mentioned in #3519 (comment)

.gitattributes

@@ -1 +1 @@
-* text=auto
+* text=auto eol=lf

.github/workflows/build.yml

@@ -42,6 +42,7 @@ jobs:
           pip install pandas==0.25.3 numpy==1.17.5
       - name: Test that schema generation has no effect
         run: |
+          pip install vl-convert-python
           python tools/generate_schema_wrapper.py
           # This gets the paths of all files which were either deleted, modified
           # or are not yet tracked by Git
@@ -60,6 +61,7 @@ jobs:
           if [ ${#files_cleaned[@]} -gt 0 ]; then
               echo "The code generation modified the following files:"
               echo $files
+              git diff
               exit 1
           fi
       - name: Test with pytest

altair/utils/theme.py

@@ -14,14 +14,14 @@
 
 if TYPE_CHECKING:
     from altair.utils.plugin_registry import PluginEnabler
-    from altair.vegalite.v5.theme import _ThemeName
+    from altair.vegalite.v5.theme import AltairThemes, VegaThemes
 
 ThemeType = Callable[..., dict]
 
 
 class ThemeRegistry(PluginRegistry[ThemeType, dict]):
     def enable(
-        self, name: LiteralString | _ThemeName | None = None, **options
+        self, name: LiteralString | AltairThemes | VegaThemes | None = None, **options
     ) -> PluginEnabler:
         """
         Enable a theme by name.

altair/vegalite/v5/schema/_typing.py

@@ -56,6 +56,7 @@
     "TitleOrient_T",
     "TypeForShape_T",
     "Type_T",
+    "VegaThemes",
     "WindowOnlyOp_T",
 ]
 
@@ -76,6 +77,22 @@ def func(
     ): ...
 """
 
+VegaThemes: TypeAlias = Literal[
+    "carbong10",
+    "carbong100",
+    "carbong90",
+    "carbonwhite",
+    "dark",
+    "excel",
+    "fivethirtyeight",
+    "ggplot2",
+    "googlecharts",
+    "latimes",
+    "powerbi",
+    "quartz",
+    "urbaninstitute",
+    "vox",
+]
 Map: TypeAlias = Mapping[str, Any]
 AggregateOp_T: TypeAlias = Literal[
     "argmax",