Brian Wilkerson
2556d0155c
Change-Id: Ic2954ff86e4fa36ea12e96ffebef6d5621137eb5 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/404522 Reviewed-by: Samuel Rawlins <srawlins@google.com> Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
2.5 KiB
Code completion
This document describes how code completion is implemented and how to fix bugs and extend it.
Basic operation
Code completion begins with the receipt of either a completion.getSuggestions2
request (from the legacy protocol) or a textDocument/completion request (from
LSP). When the request is received the appropriate handler is invoked. The
handler will compute a list of completion suggestions and will then translate
the suggestions into the form required by the protocol.
Code completion is supported in .dart files as well as in the pubspec.yaml,
analysis_options.yaml, and fix_data.yaml files.
Dart completion suggestions are computed using the DartCompletionManager by
invoking either the method computeSuggestions (for the legacy protocol) or
computeFinalizedCandidateSuggestions. (The legacy protocol will be changed to
use computeFinalizedCandidateSuggestions in the near future.)
The completion manager computes suggestions in two "passes".
-
The
InScopeCompletionPasscomputes suggestions for every appropriate element whose name is visible in the name scope surrounding the completion location. -
The
NotImportedCompletionPasscomputes suggestions for elements that are not yet visible in the name scope surrounding the completion location. This pass is skipped if there isn't time left in thebudgetor if there are already enough suggestions that the not-yet-imported elements wouldn't be sent anyway.
Maintaining and improving
The easiest way to fix bugs or add support for new features is to start by
writing a test in the directory test/services/completion/dart/location. These
tests are grouped based on the location in the grammar at which completion is
being requested.
When you have a test that's failing, add a breakpoint to
InScopeCompletionPass.computeSuggestions. When the debugger stops at the
breakpoint, hover over _completionNode to see what kind of node will be
visited. Add a breakpoint in the corresponding visit method and resume
execution. (If the visit method if it doesn't already exist, then add it and
restart the debugger).
New language features
If a new language feature is being introduced that adds new syntax, then code
completion support will need to be updated. If the changes are limited to
updating an existing node then you should be able to use the method above to
update the corresponding visit method. If the changes required the addition of
some new subclasses of AstNode, then you'll likely need to add a new visit
method for the added nodes.