detect non-local sql tables

[mbostock]

Fixes #1635.

[Fil]

We can probably refine a little with this change:

diff --git a/src/render.ts b/src/render.ts
index 926f24e1..4b2f2efe 100644
--- a/src/render.ts
+++ b/src/render.ts
@@ -59,7 +59,7 @@ if (location.pathname.endsWith("/")) {
 import ${preview || page.code.length ? `{${preview ? "open, " : ""}define} from ` : ""}${JSON.stringify(
     resolveImport("observablehq:client")
   )};${
-    files.size || data?.sql
+    files.size
       ? `\nimport {registerFile${data?.sql ? ", FileAttachment" : ""}} from ${JSON.stringify(
           resolveImport("observablehq:stdlib")
         )};`

and skip an unnecessary import of stdlib. It passes all the tests but at this point I'm wary of introducing a last-minute bug.

[mbostock]

Okay, added. I tested, but I can’t load the Parquet file from blobs.duckdb.org anymore because of a CORS error, which is odd because I thought it worked before. The generated code looks fine though. 🤷

[Fil]

It worked before for me too, and now I also got the CORS error. But substituting a different URL confirms this works.

(We still have <link rel="modulepreload" href="./_observablehq/stdlib.c0fee887.js">, so maybe it isn't much better.)

[mbostock]

I don’t think it’s possible to avoid loading the Observable standard library entirely; see src/client/main.js. Still fine to avoid the unnecessary import though and save a few bytes. 😁