fix: preselect RetroArch in a system's install box

The box showed the first setup by name, AmberELEC on 17 system pages,
under Windows tabs. It now selects RetroArch, which runs on every system
the box has a tab for, else a setup the release publishes a ZIP for.

scripts/generate_site.py

@@ -9114,6 +9114,21 @@ def _install_args(platform: str, system: str, shell: str) -> str:
     return f"--platform {platform} --system {quoted}"
 
 
+def _default_setup(declared: list[tuple[str, str]]) -> tuple[str, str]:
+    """The setup an install box shows before the reader picks one.
+
+    The first in alphabetical order was AmberELEC on 17 system pages, a
+    handheld system under a Windows tab. RetroArch runs on every OS the box
+    has a tab for. Without it, a setup the release publishes a ZIP for,
+    the ones most people download (`release_pack`).
+    """
+    for wanted in (lambda p: p == "retroarch", has_release_pack):
+        chosen = next((pair for pair in declared if wanted(pair[0])), None)
+        if chosen:
+            return chosen
+    return declared[0]
+
+
 def _install_picker(declared: list[tuple[str, str]]) -> list[str]:
     """One command, for the setup the reader picks, under the OS tabs.
 
@@ -9128,15 +9143,16 @@ def _install_picker(declared: list[tuple[str, str]]) -> list[str]:
         return html.escape(text, quote=False).replace('"', """)
 
     names = Counter(platform for platform, _system in declared)
+    lead = _default_setup(declared)
     options = "".join(
-        f'<option value="{attribute(platform)}" '
-        f'data-sh="{attribute(_install_args(platform, system, "sh"))}" '
+        f'<option value="{attribute(platform)}"'
+        + (" selected" if (platform, system) == lead else "")
+        + f' data-sh="{attribute(_install_args(platform, system, "sh"))}" '
         f'data-ps="{attribute(_install_args(platform, system, "powershell"))}">'
         + html.escape(_platform_display(platform) + (f" ({system})" if names[platform] > 1 else ""),
                       quote=False)
         + "</option>"
         for platform, system in declared)
-    lead = declared[0]
     args = {key: _install_args(*lead, TERMINALS[key][2]) for key in INSTALL_PICKER_OSES}
     return [
         "Each platform names the system its own way.",

tests/test_site_density_cards.py

@@ -193,11 +193,23 @@ class AnInstallBoxShowsOneCommand(unittest.TestCase):
         self.assertEqual(re.findall(r'<TabItem label="([^"]+)"', tabs),
                          ["Windows", "macOS", "Linux", "Steam Deck"])
         self.assertEqual(tabs.count("--platform"), 4)
-        self.assertEqual(tabs.count("--platform emudeck --system sony-psp"), 4)
+        # RetroArch, which runs on each tab's system, not the first by name.
+        self.assertEqual(tabs.count("--platform retroarch --system"), 4)
+
+    def test_the_default_setup(self) -> None:
+        """AmberELEC led 17 system pages, a handheld system under the
+        Windows tab, for being first in alphabetical order."""
+        self.assertEqual(gs._default_setup([("amberelec", "psx"), ("retroarch", "Sony - PlayStation")]),
+                         ("retroarch", "Sony - PlayStation"))
+        self.assertEqual(gs._default_setup([("amberelec", "x"), ("batocera", "x")]), ("batocera", "x"))
+        self.assertEqual(gs._default_setup([("amberelec", "x"), ("knulli", "x")]), ("amberelec", "x"))
+        select = re.search(r"<select>(.*?)</select>", self.text).group(1)
+        self.assertEqual(re.findall(r'<option value="([^"]+)" selected', select), ["retroarch"])
 
     def test_the_setup_list_carries_every_command(self) -> None:
         select = re.search(r"<select>(.*?)</select>", self.text).group(1)
-        options = re.findall(r'<option value="([^"]+)" data-sh="([^"]+)" data-ps="([^"]+)">', select)
+        options = re.findall(r'<option value="([^"]+)"(?: selected)? data-sh="([^"]+)" data-ps="([^"]+)">',
+                             select)
         self.assertEqual([value for value, _sh, _ps in options], ["emudeck", "retroarch", "retrobat"])
         self.assertIn(("retrobat", "--platform retrobat --system 'Neo Geo'",
                        "--platform retrobat --system 'Neo Geo'"), options)

website/src/scripts/site.ts

@@ -1086,7 +1086,7 @@ const copyButtons = () => {
 };
 
 // A system's install box: one command, for the setup picked in its list,
-// under the site's OS tabs. The box is built with the first setup's command;
+// under the site's OS tabs. The box is built with its selected setup's command;
 // the choice rewrites the options of each command and its copy text, and is
 // remembered for the next box and the next page. Without this script the
 // picker stays hidden and the list of every command shows instead.