Parcel plugin dev dep cache invalidation and hot reloading #5802
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…validation # Conflicts: # yarn.lock
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This doesn't introduce any issues in our app, so I'm on board with merging it. Though it would probably benefit from a technical review from @padmaia 😅 |
wbinnssmith
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Feb 26, 2021
mischnic
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| config.shouldReload(); | ||
| contents.__contains_functions = true; | ||
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| // Also add the config as a dev dependency so we attempt to reload in watch mode. |
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Couldn't config.getConfig do this for JS configs? loadConfig in utils does checks for endsWith(".js") anyway
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Good idea, will do in a follow up pr.
mischnic
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Mar 1, 2021
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T-377 T-383
This tracks dev dependencies (e.g. parcel plugins) in the request graph so that we invalidate when they are updated. There are dev_dep_request nodes in the graph which are connected to all of the files that the plugins include via require (tracked by the NodePackageManager). They also store a hash of all of these files. When a file changes, it invalidates the dev_dep_request, which in turns invalidates the asset_request. When the asset request is re-run, all of the valid dev_dep_requests are sent to the worker with their hash. This way we avoid recomputing the hash on each run, except if the dev dep is invalid.
The dev_dep_request nodes are shared between multiple asset_requests. This reduces the number of edges in the graph because only one edge is needed from asset_request to dev_dep_request rather than an edge to each individual file. It is possible, however, for multiple dev_dep_requests for the same plugin to exist, for example, due to conditional requires. A plugin may require different dependencies depending on the asset (e.g. parcel uses lazy requires that only load a module once it is used). The dependencies are recomputed for each request (though individual file hashes are cached during builds), and a new node will be created for each unique hash.
Aside from enabling cache invalidation for plugins (supporting manual editing of node_modules for debugging, patch-package, local plugins, etc.), this also enables HMR for parcel plugins and their dependencies. Since we already watch all dependencies and trigger a rebuild, we just need to clear the node require cache for that plugin and pretty much get HMR for free. This lets you work on a Parcel plugin or other dev dependency and see the results immediately without restarting the process. 😄
Parcel.Plugin.HMR.mov