Open jsnajdr opened 5 years ago
We recommend disable SplitChunksPlugin
when you want to use HMR
, it is very hard to implement
And maybe won't fix
Also please provide minimum reproducible test cases (some of them can be fixed like Fallback to "last script tag" almost never works
)
We recommend disable SplitChunksPlugin when you want to use HMR, it is very hard to implement
That still leaves two of three bugs: async loading and Promise.then
, and unreliable last script
tag.
Could you shed some light on why the "last script
tag" code is there at all? It's very easy to break -- why not just look at document.currentScript
and reject the hot update if it's null
?
Maybe it is bug, sometimes bugs happen, you can send a PR with fixes
Pinging @ScriptedAlchemy who seems to be the original author of the HMR code and might know the rationale for the "last script
tag" code.
@jsnajdr anyway if you provide reproducible examples it help to use fix problem faster
anyway if you provide reproducible examples it help to use fix problem faster
Last time I did that in #253, after a very similar conversation, it didn't help. I'd be very happy to spend my time creating and testing a patch though. Are there any suggestions on how to figure out the chunk IDs from module ID inside the webpack runtime? That would help implement the hot reloading reliably.
@jsnajdr #253 will be solved in webpack@5, we can't do something in webpack@4, it is breaking change.
Are there any suggestions on how to figure out the chunk IDs from module ID inside the webpack runtime?
module.id
module.id
Can you expand on that? The HMR code already knows the module ID. It needs to figure out the chunk URLs to reload.
No information about chunk
Are there any suggestions on how to figure out the chunk IDs from module ID inside the webpack runtime? That would help implement the hot reloading reliably.
It is possible to collect moduleId => chunkIds map at compile time, pass it to runtime chunk and use from HMR.
Other example:
git clone https://gist.github.com/andersk/2d45d4363478b22e998e177836ebce12 css-hmr-test
cd css-hmr-test
npm install
npx webpack serve --hot
Also need test with [hash]
/[fullhash]
/[contenthash]
Does this means experiment: { css: true }
would have this problem too?
I reproduce the problem in Webpack5 with experiment: { css: true }
. I will dig into it to see how to fix this.
The HMR code needs to do some magic to convert the
moduleId
of the updated module to the URLs of the CSS chunks that contain the module. These URLs then need to be reloaded.Trying to enable it in Calypso revealed at least three bugs:
Doesn't work with async-loaded chunks
getCurrentScriptUrl
relies ondocument.currentScript
, which works when the chunk is loaded withscript
tag, but not when a chunk is loaded asynchronously. Then the module is evaluated in aPromise.then
handler anddocument.currentScript
isnull
. No hot reload.Is not reliable with shared chunks With shared async chunks optimized by
SplitChunksPlugin
, it commonly happens that a module code is duplicated in multiple chunks. To reliably hot-reload their CSS, we need to reload all the CSS chunks where the module is bundled. That doesn't happen at this moment. Only the chunk that was used to actually execute the module is reloaded.Fallback to "last
script
tag" almost never works WhengetCurrentScriptUrl
can't finddocument.currentScript
, it falls back to using thesrc
attribute of the lastscript
tag in the document. That works for very simple apps that load a single JS bundle, but fails in cases like:moduleId
script
tag is not owned by webpack, but loads something else. For example, analytics from a 3rd party sourcescript
doesn't have asrc
attribute, but is an inline script. Then the HMR code will crash withTypeError: Cannot read property 'some' of null