FetchBodyPrecondition.md

Copy of w3c/ServiceWorker#452 (comment)

In the following plans, fetch() is omitted since fetch(req) runs new Request(req), and therefore it's sufficient to discuss only new Request(req).

(X) Lock + used flag

Request

• a Request has a boolean used flag which is initially set to false
• req.bodyUsed = used flag
• unavailable = (req.body is locked) || (used flag is set)
• The following operations fail when unavailable is true. Otherwise, they set used flag to true, acquire the lock of req.body and release it when done (req.body becomes "closed" when done).
  • req.arrayBuffer()
  • req.blob()
  • req.formData()
  • req.json()
  • req.text()
  • new Request(req)
  • cache.put(req, res)
• req.clone() fail when unavailable is set.

Response

• a Response has a boolean used flag which is initially set to false
• res.bodyUsed = used flag
• unavailable = (res.body is locked) || (used flag is set)
• The following operations fail when unavailable is true. Otherwise, they set used flag to true, acquire the lock of res.body and release it when done.
  • res.arrayBuffer()
  • res.blob()
  • res.formData()
  • res.json()
  • res.text()
  • e.respondWith(res)
  • cache.put(req, res)
• res.clone() fail when unavailable is set.

(A)'' Lock + body passed flag

Request

• a Request has a boolean body passed flag
• req.bodyUsed = (req.body is locked) || req's body passed flag is set
• The following operations fail when req.bodyUsed is set. Otherwise, they acquire the lock of req.body and release it when done.
  • req.arrayBuffer()
  • req.blob()
  • req.formData()
  • req.json()
  • req.text()
• req.clone() fail when req.bodyUsed is set.
• The following operations fail when req.bodyUsed is set. Otherwise, they set req's body passed flag, acquire the lock of req.body and release it when done (req.body becomes "closed" when done).
  • new Request(req)
  • cache.put(req, res)

Response

• a Response has a boolean body passed flag
• res.bodyUsed = (res.body is locked) || res's body passed flag is set
• The following operations fail when res.bodyUsed is set. Otherwise, they acquire the lock of res.body and release it when done.
  • res.arrayBuffer()
  • res.blob()
  • res.formData()
  • res.json()
  • res.text()
• res.clone() fail when res.bodyUsed is set.
• The following operations fail when res.bodyUsed is set. Otherwise, they set res's body passed flag, acquire the lock of res.body and release it when done (res.body becomes "closed" when done).
  • e.respondWith(res)
  • cache.put(req, res)

Note

• a Response/Request with body passed flag is unset but .body "errored" is considered to be one whose headers were received successfully but body wasn't
• a Response/Request with body passed flag set is considered to be invalid

(A)

Same as (A) but the following operations set body passed flag, confiscate the underlying source and queue from res.body and error it.

• new Request(req)
• cache.put(req, res)
• e.respondWith(res)
• cache.put(req, res)

(A)'

Same as (A) but the following operations set body passed flag, confiscate the underlying source and queue from res.body and close it.

• new Request(req)
• cache.put(req, res)
• e.respondWith(res)
• cache.put(req, res)

(B) Permanent lock

Request

• req.bodyUsed = req.body is locked
• The following operations fail when req.body is locked. Otherwise, they acquire the lock of req.body and release it when done.
  • req.arrayBuffer()
  • req.blob()
  • req.formData()
  • req.json()
  • req.text()
• req.clone() fails when req.body is locked.
• The following operations fail when req.body is locked. Otherwise, they acquire the lock of req.body and never release it.
  • new Request(req)
  • cache.put(req, res)

Response

• res.bodyUsed = res.body is locked
• The following operations fail when res.body is locked. Otherwise, they acquire the lock of res.body and release it when done.
  • res.arrayBuffer()
  • res.blob()
  • res.formData()
  • res.json()
  • res.text()
• res.clone() fails when res.body is locked.
• The following operations fail when res.body is locked. Otherwise, they acquire the lock of res.body and never release it.
  • e.respondWith(res)
  • cache.put(req, res)

Note

• Needs change on the Streams API spec to hold the lock of a stream even after draining it.

(C) Only lock

Request

• req.bodyUsed = req.body is locked
• The following operations fail when req.body is locked. Otherwise, they acquire the lock of req.body and release it when done.
  • req.arrayBuffer()
  • req.blob()
  • req.formData()
  • req.json()
  • req.text()
  • new Request(req)
  • cache.put(req, res)
• req.clone() fails when req.body is locked.

Response

• res.bodyUsed = res.body is locked
• The following operations fail when res.body is locked. Otherwise, they acquire the lock of res.body and release it when done.
  • res.arrayBuffer()
  • res.blob()
  • res.formData()
  • res.json()
  • res.text()
  • e.respondWith(res)
  • cache.put(req, res)
• res.clone() fails when res.body is locked.