x/tools/gopls: no completions provided in some seemingly straightforward cases

[cespare]

gopls version

Build info
----------
golang.org/x/tools/gopls v0.16.2
    golang.org/x/tools/gopls@v0.16.2 h1:K1z03MlikHfaMTtG01cUeL5FAOTJnITuNe0TWOcg8tM=
    github.com/BurntSushi/toml@v1.2.1 h1:9F2/+DoOYIOksmaJFPw1tGFy1eDnIJXg+UHjuD8lTak=
    github.com/google/go-cmp@v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
    golang.org/x/exp/typeparams@v0.0.0-20221212164502-fae10dda9338 h1:2O2DON6y3XMJiQRAS1UWU+54aec2uopH3x7MAiqGW6Y=
    golang.org/x/mod@v0.20.0 h1:utOm6MM3R3dnawAiJgn0y+xvuYRsm1RKM/4giyfDgV0=
    golang.org/x/sync@v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
    golang.org/x/telemetry@v0.0.0-20240829154258-f29ab539cc98 h1:Wm3cG5X6sZ0RSVRc/H1/sciC4AT6HAKgLCSH2lbpR/c=
    golang.org/x/text@v0.16.0 h1:a94ExnEXNtEwYLGJSIUxnWoxoRz/ZcCsV63ROupILh4=
    golang.org/x/tools@v0.22.1-0.20240829175637-39126e24d653 h1:6bJEg2w2kUHWlfdJaESYsmNfI1LKAZQi6zCa7LUn7eI=
    golang.org/x/vuln@v1.0.4 h1:SP0mPeg2PmGCu03V+61EcQiOjmpri2XijexKdzv8Z1I=
    honnef.co/go/tools@v0.4.7 h1:9MDAWxMoSnB6QoSqiVr7P5mtkT9pOc1kSxchzPCnqJs=
    mvdan.cc/gofumpt@v0.6.0 h1:G3QvahNDmpD+Aek/bNOLrFR2XC6ZAdo62dZu65gmwGo=
    mvdan.cc/xurls/v2@v2.5.0 h1:lyBNOm8Wo71UknhUs4QTFUNNMyxy2JEIaKKo0RWOh+8=
go: go1.23.0

go env

not relevant

What did you do?

I have a text file like this, where | represents the cursor position:

package main

func main() {
	foobar := []int{1, 2, 3}
	if len(foo|
}

What did you see happen?

I invoked completion (the LSP action is textDocument/completion) and got zero results.

I also used the gopls rpc trace log to verify that gopls got the request and was sending back zero items, so it's not related to some editor integration issue.

What did you expect to see?

I want to see foobar as a suggested completion (probably the only one).

Here are some similar situations where foobar is the suggested completion:

package main

func main() {
	foobar := []int{1, 2, 3}
	foo|
}

package main

func main() {
	foobar := []int{1, 2, 3}
	len(foo|
}

package main

func main() {
	foobar := []int{1, 2, 3}
	if foo|
}

package main

func main() {
	foobar := []int{1, 2, 3}
	if len(foo|)
}

Editor and settings

No response

Logs

The completion trace request/response looks like this:

[Trace - 11:52:32.791 AM] Sending request 'textDocument/completion - (22)'.
Params: {"position":{"character":12,"line":8},"textDocument":{"uri":"file:\/\/\/..path elided...\/x\/x.go"}}


[Trace - 11:52:32.792 AM] Received response 'textDocument/completion - (22)' in 0ms.
Result: {"isIncomplete":true,"items":[]}

[gabyhelp]

Related Issues and Documentation

• x/tools/gopls: `TestXxx()` completions not working when location followed by newline, due to parser error recovery #61371
• x/tools/gopls: core functionality does not work in vendor directories #53756
• x/tools/gopls: completion doesn't suggest items following invalid code #31687 (closed)
• x/tools/gopls: add end of line commas during completion #67246
• x/tools/gopls: test completions duplicates text #56852 (closed)
• x/tools/cmd/gopls: completion returns error when there are zero completions #31301 (closed)
• x/tools/gopls: completion stops working when using labels #46650
• x/tools/gopls: unimported completions not (consistently) offered #38764 (closed)
• x/tools/gopls: bad completion candidate for variadic call where method returns slice #42691 (closed)
• x/tools/gopls: suggested completions include many irrelevant, non-deterministic entries #43374

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