Chris Amow
e69d1c190f
The trendline slope fix was already correct — measured on the live chart, the two rendered segments came out at screen slopes 0.4910 and 0.4903, collinear. It still reproduced in the browser because the browser was not running it. StaticFiles sends an ETag but no Cache-Control, and the asset URLs carried no version, so nothing forced a refetch. A tab left open across an edit never fetches at all: it keeps executing the JavaScript it loaded when the page was first opened. Every fix since that tab was opened was invisible in it. The page now stamps its own asset URLs with a digest of their contents and is itself served no-store. Hashing rather than stamping mtimes, because a deploy checks every file out fresh and would otherwise invalidate assets that never changed. This also removes a trap the README already half-documented for deploys: an /api-only change leaves the HTML byte-identical, and until now a JavaScript change could leave the served page byte-identical too. The debug handle used to measure the geometry is kept deliberately. Chart rendering bugs are invisible from the outside, and window.__chart.lineData() against timeToCoordinate() is what settled this one. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
70 lines
2.1 KiB
Python
70 lines
2.1 KiB
Python
"""chart.amow.com FastAPI backend."""
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import asyncio
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from contextlib import asynccontextmanager
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from pathlib import Path
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import re
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from hashlib import sha256
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from fastapi import FastAPI
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from fastapi.responses import HTMLResponse
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from fastapi.staticfiles import StaticFiles
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from app.api.meta import router as meta_router
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from app.api.routes import router as api_router
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from app.api.ws import router as ws_router
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from app.config import Settings
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from app.runtime import Runtime
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BASE_DIR = Path(__file__).parent
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STATIC_DIR = BASE_DIR / "static"
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@asynccontextmanager
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async def lifespan(app: FastAPI):
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runtime = Runtime(Settings())
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app.state.runtime = runtime
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task = await runtime.start()
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yield
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runtime.stream.stop()
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task.cancel()
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try:
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await task
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except asyncio.CancelledError:
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pass
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app = FastAPI(title="chart", lifespan=lifespan)
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app.mount("/static", StaticFiles(directory=STATIC_DIR), name="static")
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app.include_router(meta_router)
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app.include_router(api_router)
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app.include_router(ws_router)
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ASSET_REF = re.compile(r'((?:src|href)="/static/[^"?]+)"')
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def asset_version() -> str:
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"""A digest of the served assets, so the URL changes iff the content does.
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StaticFiles sends an ETag but no Cache-Control, so a browser is free to keep
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using the copy it already has — and a tab left open simply never fetches
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again. That turned a fixed bug into a bug that still reproduced, because the
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page was running the JavaScript it had loaded hours earlier.
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Hashing rather than stamping mtimes: a deploy checks every file out fresh,
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which would otherwise invalidate assets that never changed.
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"""
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digest = sha256()
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for path in sorted(STATIC_DIR.glob("*.*")):
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digest.update(path.read_bytes())
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return digest.hexdigest()[:12]
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@app.get("/")
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def index():
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html = (STATIC_DIR / "index.html").read_text(encoding="utf-8")
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html = ASSET_REF.sub(rf'\1?v={asset_version()}"', html)
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# The document itself must never be cached, or the versioned URLs inside it
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# are the stale thing instead.
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return HTMLResponse(html, headers={"Cache-Control": "no-store"})
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