This PR adds support for code actions that resolve 'unknown identifier'
errors by either importing the missing declaration or by changing the
identifier to one from the environment.
<details>
<summary>Demo (Click to open)</summary>
</details>
Specifically, the following kinds of code actions are added by this PR,
all of which are triggered on 'unknown identifier' errors:
- A code action to import the module containing the identifier at the
text cursor position.
- A code action to change the identifier at the text cursor position to
one from the environment.
- A source action to import the modules for all unambiguous identifiers
in the file.
### Details
When clicking on an identifier with an 'unknown identifier' diagnostic,
after a debounce delay of 1000ms, the language server looks up the
(potentially partial) identifier at the position of the cursor in the
global reference data structure by fuzzy-matching against all
identifiers and collects the 10 closest matching entries. This search
accounts for open namespaces at the position of the cursor, including
the namespace of the type / expected type when using dot notation. The
10 closest matching entries are then offered to the user as code
actions:
- If the suggested identifier is not contained in the environment, a
code action that imports the module that the identifier is contained in
and changes the identifier to the suggested one is offered. The
suggestion is inserted in a "minimal" manner, i.e. by accounting for
open namespaces.
- If the suggested identifier is contained in the environment, a code
action that only changes the identifier to the suggested one is offered.
- If the suggested identifier is not contained in the environment and
the suggested identifier is a perfectly unambiguous match, a source
action to import all unambiguous in the file is offered.
The source action to import all unambiguous identifiers can also always
be triggered by right-clicking in the document and selecting the 'Source
Action...' entry.
At the moment, for large projects, the search for closely matching
identifiers in the global reference data structure is still a bit slow.
I hope to optimize it next quarter.
### Implementation notes
- Since the global reference data structure is in the watchdog process,
whereas the elaboration information is in the file worker process, this
PR implements support for file worker -> watchdog requests, including a
new `$/lean/queryModule` request that can be used by the file worker to
request global identifier information.
- To identify 'unknown identifier' errors, several 'unknown identifier'
errors in the elaborator are tagged with a new tag.
- The debounce delay of 1000ms is necessary because VS Code will
re-request code actions while editing an unknown identifier and also
while hovering over the identifier.
- We also implement cancellation for these 'unknown identifier' code
actions. Once the file worker responds to the request as having been
cancelled, the watchdog cancels its computation of all corresponding
file worker -> watchdog requests, too.
- Aliases (i.e. `export`) are currently not accounted for. I've found
that we currently don't handle them correctly in auto-completion, too,
so we will likely add support for this later when fixing the
corresponding auto-completion issue.
- The new code actions added by this request support incrementality.
This PR fixes several inlay hint race conditions that could result in a
violation of the monotonic progress assumption, introduced in #7149.
Specifically:
- In rare circumstances, it could happen that stateful LSP requests were
executed out-of-order with their `didChange` handlers, as both requests
and the `didChange` handlers waited on `lake setup-file` to complete,
with the latter running those handlers in a dedicated task afterwards.
This meant that a request could be added to the stateful LSP handler
request queue before the corresponding `didChange` call that actually
came before it. This PR resolves this issue by folding the task that
waits for `lake setup-file` into the `RequestContext`, which ensures
that we only need to wait for it when actually executing the request
handler.
- While #7164 fixed the monotonic progress assertion violation that was
caused by `$/cancelRequest`, it did not account for our internal notion
of silent request cancellation in stateful LSP requests, which we use to
cancel the inlay hint edit delay when VS Code fails to emit a
`$/cancelRequest` notification. This issue is resolved by always
producing the full finished prefix of the command snapshot queue, even
on cancellation. Additionally, this also fixes an issue where in the
same circumstances, the language server could produce an empty inlay
hint response when a request was cancelled by our internal notion of
silent request cancellation.
- For clients that use `fullChange` `didChange` notifications (e.g. not
VS Code), we would get several aspects of stateful LSP request
`didChange` state handling wrong, which is also addressed by this PR.
This PR ensures that all tasks in the language server either use
dedicated tasks or reuse an existing thread from the thread pool. This
ensures that elaboration tasks cannot prevent language server tasks from
being scheduled. This is especially important with parallelism right
around the corner and elaboration becoming more likely to starve the
language server of computation, which could drive up language server
latencies significantly on machines with few cores.
Specifically, all language server tasks are refactored to use a new thin
`ServerTask` API wrapper with a single "costly" vs "cheap" dimension,
where costly tasks are always scheduled as dedicated tasks, and cheap
tasks are always made to either run on the calling thread or to reuse
the thread of the task being mapped on by using the `sync` flag.
ProofWidgets4 adaption PR:
https://github.com/leanprover-community/ProofWidgets4/pull/106
### Other changes
- This PR makes several tasks dedicated that weren't dedicated before,
and uses `sync := true` for some others. The rules for this are
described in the module docstring of `ServerTask.lean`.
- Most notably, the reporting task in the file worker was *not* a
dedicated task before this PR, which could easily lead to thread pool
starvation on successive changes. It also did not support cancellation.
This PR ensures that it does.
### Breaking changes
- `RequestTask` and the request-oriented snapshot API are refactored to
use `ServerTask` instead of `Task`. All functions in `Task` have close
analogues in `ServerTask`, and functions on `RequestTask` now need to
distinguish between whether a `map` or a `bind` is cheap or costly. This
affects all downstream users of `RequestM`, e.g. tools that extend the
language server with their own requests, or some users of the RPC
mechanism.
- The following unused functions of the `AsyncList` API have been
deleted: `append`, `unfoldAsync`, `getAll`, `waitHead?`, `cancel`
This PR implements a number of refinements for the auto-implicit inlay
hints implemented in #6768.
Specifically:
- In #6768, there was a bug where the inlay hint edit delay could
accumulate on successive edits, which meant that it could sometimes take
much longer for inlay hints to show up. This PR implements the basic
infrastructure for request cancellation and implements request
cancellation for semantic tokens and inlay hints to resolve the issue.
With this edit delay bug fixed, it made more sense to increase the edit
delay slightly from 2000ms to 3000ms.
- In #6768, we applied the edit delay to every single inlay hint request
in order to reduce the amount of inlay hint flickering. This meant that
the edit delay also had a significant effect on how far inlay hints
would lag behind the file progress bar. This PR adjusts the edit delay
logic so that it only affects requests sent directly after a
corresponding `didChange` notification. Once the edit delay is used up,
all further semantic token requests are responded to without delay, so
that the only latency that affects how far the inlay hints lag behind
the progress bar is how often we emit refresh requests and how long VS
Code takes to respond to them.
- For inlay hints, refresh requests are now emitted 500ms after a
response to an inlay hint request, not 2000ms, which means that after
the edit delay, inlay hints should only lag behind the progress bar by
about up to 500ms. This is justifiable for inlay hints because the
response should be much smaller than e.g. is the case for semantic
tokens.
- In #6768, 'Restart File' did not prompt a refresh, but it does now.
- VS Code does not immediately remove old inlay hints from the document
when they are applied. In #6768, this meant that inlay hints would
linger around for a bit once applied. To mitigate this issue, this PR
adjusts the inlay hint edit delay logic to identify edits sent from the
client as being inlay hint applications, and sets the edit delay to 0ms
for the inlay hint requests following it. This means that inlay hints
are now applied immediately.
- In #6768, hovering over single-letter auto-implicit inlay hints was a
bit finicky because VS Code uses the regular cursor icon on inlay hints,
not the thin text cursor icon, which means that it is easy to put the
cursor in the wrong spot. We now add the separation character (` ` or
`{`) preceding an auto-implicit to the hover range as well, which makes
hovering over inlay hints much smoother.
This PR adds preliminary support for inlay hints, as well as support for
inlay hints that denote the auto-implicits of a function. Hovering over
an auto-implicit displays its type and double-clicking the auto-implicit
inserts it into the text document.
This PR is an extension of #3910.
### Known issues
- In VS Code, when inserting an inlay hint, the inlay hint may linger
for a couple of seconds before it disappears. This is a defect of the VS
Code implementation of inlay hints and cannot adequately be resolved by
us.
- When making a change to the document, it may take a couple of seconds
until the inlay hints respond to the change. This is deliberate and
intended to reduce the amount of inlay hint flickering while typing. VS
Code has a mechanism of its own for this, but in my experience it is
still far too sensitive without additional latency.
- Inserting an auto-implicit inlay hint that depends on an auto-implicit
meta-variable causes a "failed to infer binder type" error. We can't
display these meta-variables in the inlay hint because they don't have a
user-displayable name, so it is not clear how to resolve this problem.
- Inlay hints are currently always resolved eagerly, i.e. we do not
support the `textDocument/inlayHint/resolve` request yet. Implementing
support for this request is future work.
### Other changes
- Axioms did not support auto-implicits due to an oversight in the
implementation. This PR ensures they do.
- In order to reduce the amount of inlay hint flickering when making a
change to the document, the language server serves old inlay hints for
parts of the file that have not been processed yet. This requires LSP
request handler state (that sometimes must be invalidated on
`textDocument/didChange`), so this PR introduces the notion of a
stateful LSP request handler.
- The partial response mechanism that we use for semantic tokens, where
we simulate incremental LSP responses by periodically emitting refresh
requests to the client, is generalized to accommodate both inlay hints
and semantic tokens. Additionally, it is made more robust to ensure that
we never emit refresh requests while a corresponding request is in
flight, which causes VS Code to discard the respond of the request, as
well as to ensure that we keep prompting VS Code to send another request
if it spuriously decides not to respond to one of our refresh requests.
- The synthetic identifier of an `example` had the full declaration as
its (non-canonical synthetic) range. Since we need a reasonable position
for the identifier to insert an inlay hint for the auto-implicits of an
`example`, we change the (canonical synthetic) range of the synthetic
identifier to that of the `example` keyword.
- The semantic highlighting request handling is moved to a separate
file.
### Breaking changes
- The semantic highlighting request handler is not a pure request
handler anymore, but a stateful one. Notably, this means that clients
that extend the semantic highlighting of the Lean language server with
the `chainLspRequestHandler` function must now use the
`chainStatefulLspRequestHandler` function instead.
