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RFC - ShakeSession and shakeRunGently (2) #555
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Currently we start a new Shake session for every interaction with the Shake database, including type checking, hovers, code actions, completions, etc. Since only one Shake session can ever exist, we abort the active session if any in order to execute the new command in a responsive manner. This is suboptimal in many, many ways: - A hover in module M aborts the typechecking of module M, only to start over! - Read-only commands (hover, code action, completion) need to typecheck all the modules! (or rather, ask Shake to check that the typechecks are current) - There is no way to run non-interfering commands concurrently This is an experiment inspired by the 'ShakeQueue' of @mpickering, and the follow-up discussion in mpickering#7 We introduce the concept of the 'ShakeSession' as part of the IDE state. The 'ShakeSession' is initialized by a call to 'shakeRun', and survives until the next call to 'shakeRun'. It is important that the session is restarted as soon as the filesystem changes, to ensure that the database is current. The 'ShakeSession' enables a new command 'shakeRunGently', which appends work to the existing 'ShakeSession'. This command can be called in parallel without any restriction.
shakeRunGently enabled massive speed ups for: - Hover - Code Actions But not for completions, which are usually requested immediately after a file edit, which in turn triggers a non gentle shakeRun, which resets the ShakeSession, and therefore getCompletions finds a cold ShakeSession and is slow as a result. The obvious question then, is why not make every shakeRun a gentle one? The non gentle shakeRun disappears, and with it the ability to cancel Shake actions Is cancelling actions an important feature? - We can now run multiple actions concurrently, so it is no longer necessary to wait until the current action finishes. This removes the need for cancellation in user triggered actions, like hover, code actions and completions. - Thanks to recent changes in ghcide, most actions have become cheap enough. I wonder if this is enough to remove the need for aborting typechecks
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This is a failed attempt. The 'ShakeSession' does not see filesystem edits unless it is restarted to update the Shake database. |
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This Request For Comments builds on top of #554 addressing the performance of completions.
shakeRunGentlyenabled massive speed ups for:But not for completions, which are usually requested immediately after a file
edit, which in turn triggers a non gentle
shakeRun, which resets theShakeSession, and thereforegetCompletionsfinds a coldShakeSessionand is slowas a result.
The obvious question then, is why not make every
shakeRuna gentle one?The non gentle
shakeRundisappears, and with it the ability to cancel Shake actionsIs cancelling actions an important feature?
wait until the current action finishes.
This removes the need for cancellation in user triggered actions, like hover, code
actions and completions.
I wonder if this is enough to remove the need for cancelling typechecks