feat: infer mimetype from paste filename

Author: SharzyL

doc/api.md

@@ -8,7 +8,7 @@ Return the index page.
 
 Fetch the paste with name `<name>`. By default, it will return the raw content of the paste.
 
-The `Content-Type` header is set to `text/plain;charset=UTF-8`. If `<ext>` is given, the worker will infer mime-type from `<ext>` and change `Content-Type`. This method accepts the following query string parameters:
+The `Content-Type` header is set to `text/plain;charset=UTF-8`. If `<ext>` is given, the worker will infer mime-type from `<ext>` and change `Content-Type`. If the paste is uploaded with a filename, the worker will infer mime-type from the filename. This method accepts the following query string parameters:
 
 The `Content-Disposition` header is set to `inline` by default. But can be overriden by `?a` query string. If the paste is uploaded with filename, or `<filename>` is set in given request URL, `Content-Disposition` is appended with `filename*` indicating the filename (with `<ext>` if it exists).
 

src/handlers/handleRead.ts

@@ -44,8 +44,6 @@ export async function handleGet(request: Request, env: Env, _: ExecutionContext)
     })
   }
 
-  const inferred_mime = url.searchParams.get("mime") || (ext && mime.getType(ext)) || "text/plain"
-
   const disp = url.searchParams.has("a") ? "attachment" : "inline"
 
   const item = await getPaste(env, nameFromPath)
@@ -57,6 +55,12 @@ export async function handleGet(request: Request, env: Env, _: ExecutionContext)
 
   // check `if-modified-since`
   const pasteLastModifiedUnix = item.metadata.lastModifiedAtUnix
+
+  const inferred_mime = url.searchParams.get("mime")
+    || (ext && mime.getType(ext))
+    || (item.metadata.filename && mime.getType(item.metadata.filename))
+    || "text/plain"
+
   const headerModifiedSince = request.headers.get("if-modified-since")
   if (headerModifiedSince) {
     const headerModifiedSinceUnix = Date.parse(headerModifiedSince) / 1000

test/controlHeaders.spec.ts

@@ -7,6 +7,10 @@ test("mime type", async () => {
   const ctx = createExecutionContext()
   const url = (await upload(ctx, ({ "c": genRandomBlob(1024) })))["url"]
 
+  const url_pic = (await upload(ctx, {
+    "c": {content: genRandomBlob(1024), filename: "xx.jpg"}
+  }))["url"]
+
   async function testMime(accessUrl: string, mime: string) {
     const resp = await workerFetch(ctx, accessUrl)
     expect(resp.headers.get("Content-Type")).toStrictEqual(mime)
@@ -18,6 +22,9 @@ test("mime type", async () => {
   await testMime(`${url}?mime=random-mime`, "random-mime;charset=UTF-8")
   await testMime(`${url}.jpg?mime=random-mime`, "random-mime;charset=UTF-8")
   await testMime(`${url}/test.jpg?mime=random-mime`, "random-mime;charset=UTF-8")
+
+  await testMime(url_pic, "image/jpeg;charset=UTF-8")
+  await testMime(`${url_pic}.png`, "image/png;charset=UTF-8")
 })
 
 test("cache control", async () => {