start project

app/utils/assets.py

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+"""Vite manifest reader — maps a source entry to its hashed dist path (Ch05)."""
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+from flask import Flask
+
+
+class ManifestNotFound(RuntimeError):
+    """app/static/dist/manifest.json is missing — `npm run build` hasn't been run."""
+
+
+def _load_manifest(static_dist_dir: Path) -> dict:
+    for candidate in (static_dist_dir / ".vite" / "manifest.json", static_dist_dir / "manifest.json"):
+        if candidate.exists():
+            return json.loads(candidate.read_text())
+    raise ManifestNotFound(f"No Vite manifest under {static_dist_dir} — run `npm run build`.")
+
+
+def register_asset_helper(app: Flask) -> None:
+    """Register `asset(name)` as a Jinja global (Chapter 05)."""
+    static_dist_dir = Path(app.static_folder) / "dist"
+
+    @app.context_processor
+    def inject_asset_helper():
+        def asset(name: str) -> str:
+            try:
+                manifest = _load_manifest(static_dist_dir)
+            except ManifestNotFound:
+                if app.debug:
+                    return f"/static/dist/{name}"  # tolerate an unbuilt dev checkout
+                raise
+            entry = manifest.get(name)
+            if entry is None:
+                raise KeyError(f"{name!r} not in Vite manifest.")
+            return f"/static/dist/{entry['file']}"
+
+        return {"asset": asset}