golang/go

x/tools/gopls: bad completion insertion after syntax error

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#32,510 opened on Jun 9, 2019

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NeedsInvestigationgoplshelp wanted

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Description

In this code

package foo

func foo() {
	foo(a ...interface{})
	f<>
}

Completing "f" to "foo" ends up inserting "ffoo" instead of "foo". This is because the syntax error on the previous line completely obscures the "f" *ast.Ident, so we don't detect it properly as the prefix. Perhaps if we are in a BadExpr we could "manually" detect the surrounding identifier so completion still works to some degree?

/cc @stamblerre

Contributor guide

Research direction
Examine how gopls computes completion prefix and handle cases where the prefix identifier is obscured by a syntax error (BadExpr). Look for ways to manually detect the identifier preceding the cursor position even when the AST is incomplete.
Tech stack
go
Domain
developer experience
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Gogopls
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30