feat: Adds vl_convert_to_vega_version, remove `vegalite_to_vega_ver…

…sion`

- Found this to be a much more reliable source
- Won't require manual syncing
- Can easily be replaced in the future with a public function/attribute accessible in `vl_convert` itself

#3600 (comment)

tools/generate_schema_wrapper.py

@@ -5,16 +5,19 @@
 import argparse
 import copy
 import json
+import re
 import sys
 import textwrap
 from collections import deque
 from dataclasses import dataclass
 from itertools import chain
 from operator import attrgetter
 from pathlib import Path
-from typing import TYPE_CHECKING, Any, Final, Iterable, Iterator, Literal
+from typing import TYPE_CHECKING, Any, Final, Iterable, Iterator, Literal, cast
 from urllib import request
 
+from packaging.version import Version
+
 import vl_convert as vlc
 
 sys.path.insert(0, str(Path.cwd()))
@@ -45,10 +48,73 @@
 )
 
 if TYPE_CHECKING:
+    from http.client import HTTPResponse
+
     from tools.schemapi.codegen import ArgInfo, AttrGetter
 
+
+def vl_convert_to_vega_version(
+    *,
+    version: str | None = None,
+    url_fmt: str = "https://raw.githubusercontent.com/vega/vl-convert/refs/tags/vl-convert-vendor%40{0}/vl-convert-vendor/src/main.rs",
+    prefix: bytes = b"const VEGA_PATH",
+    pattern: str = r".+\/pin\/vega@(?P<vega_version>v\d\.\d{1,3}\.\d{1,3})",
+) -> str:
+    """
+    Return the minimum supported ``vega`` release for a ``vl_convert`` version.
+
+    Parameters
+    ----------
+    version
+        A target `vl_convert` release.
+        Defaults to currently installed version.
+    url_fmt
+        Format string for source file.
+    prefix
+        Byte string prefix of target line.
+    pattern
+        Matches and extracts vega version, e.g. `"v5.30.0"`.
+
+    Examples
+    --------
+    >>> vl_convert_to_vega_version(version="0.2.0")
+    'v5.22.1'
+    >>> vl_convert_to_vega_version(version="1.0.0")
+    'v5.25.0'
+    >>> vl_convert_to_vega_version(version="1.3.0")
+    'v5.28.0'
+    >>> vl_convert_to_vega_version(version="1.6.1")
+    'v5.30.0'
+    """
+    MIN_VL_CONVERT = "0.2.0"
+    vlc_version: str = version or vlc.__version__  # pyright: ignore[reportAttributeAccessIssue]
+    if Version(vlc_version) < Version(MIN_VL_CONVERT):
+        msg = (
+            f"Operation requires `vl_convert>={MIN_VL_CONVERT!r}`\n"
+            f"but got: {version!r}"
+        )
+        raise NotImplementedError(msg)
+    with request.urlopen(url_fmt.format(vlc_version)) as response:
+        response = cast("HTTPResponse", response)
+        line = response.readline()
+        while not line.startswith(prefix):
+            line = response.readline()
+            if line.startswith(b"fn main"):
+                msg = f"Failed to find {prefix!r} in {url_fmt.format(vlc_version)}."
+                raise ValueError(msg)
+        src_line = line.decode()
+    if match := re.match(pattern, src_line):
+        return match.group("vega_version")
+    else:
+        msg = (
+            f"Failed to match a vega version specifier.\n"
+            f"{src_line=}\n{pattern=}\n{match=}\n"
+        )
+        raise NotImplementedError(msg)
+
+
 SCHEMA_VERSION: Final = "v5.20.1"
-VEGA_VERSION: Final = "v5.30.0"
+VEGA_VERSION: Final[str] = vl_convert_to_vega_version()
 
 
 HEADER_COMMENT = """\
@@ -474,15 +540,6 @@ def schema_url(version: str = SCHEMA_VERSION) -> str:
     return SCHEMA_URL_TEMPLATE.format(library="vega-lite", version=version)
 
 
-def vegalite_to_vega_version(vl_version: str, /) -> str:
-    """Return the minimum supported ``vega`` release for a ``vega-lite`` version."""
-    with request.urlopen(VL_PACKAGE_TEMPLATE.format(version=vl_version)) as response:
-        package_json = json.load(response)
-
-    version_spec = package_json["peerDependencies"]["vega"]
-    return f"v{version_spec.lstrip('^~')}"
-
-
 def download_schemafile(
     version: str, schemapath: Path, skip_download: bool = False
 ) -> Path: