This PR adds basic auto-completion support for imports. Since it still
lacks Lake support for accurate completion suggestions (cc @tydeu - we
already know what needs to be done), it falls back to traversing the
`LEAN_SRC_PATH` for available imports.
Three kinds of import completion requests are supported:
- Completion of the full `import` command. Triggered when requesting
completions in an empty space within the header.
- Known issue: It is possible to trigger this completion within a
comment in the header. Fixing this would require architecture for
parsing some kind of sub-syntax between individual commands.
- Completion of the full module name after an incomplete `import`
command.
- Completion of a partial module name with a trailing dot.
Since the set of imports is potentially expensive to compute, they are
cached for 10 seconds after the last import auto-completion request.
Closes#2655.
### Changes
This PR also makes the following changes:
- To support completions on the trailing dot, the `import` syntax was
adjusted to provide partial syntax when a trailing dot is used.
- `FileWorker.lean` was refactored lightly with some larger definitions
being broken apart.
- The `WorkerState` gained two new fields:
- `currHeaderStx` tracks the current header syntax, as opposed to
tracking only the initial header syntax in `initHeaderStx`. When the
header syntax changes, a task is launched that restarts the file worker
after a certain delay to avoid constant restarts while editing the
header. During this time period, we may still want to serve import
auto-completion requests, so we need to know the up-to-date header
syntax.
- `importCachingTask?` contains a task that computes the set of
available imports.
- `determineLakePath` has moved to a new file `Lean/Util/LakePath.lean`
as it is now needed both in `ImportCompletion.lean` and
`FileWorker.lean`.
- `forEachModuleIn` from `Lake/Config/Blob.lean` has moved to
`Lean/Util/Path.lean` as it is a generally useful utility function that
was useful for traversing the `LEAN_SRC_PATH` as well.
### Tests
Unfortunately, this PR lacks tests since the set of imports available in
`tests/lean/interactive` will not be stable. In the future, I will add
support for testing LSP requests in full project setups, which is when
tests for import auto-completion will be added as well.
