x/tools/gopls: autocomplete for CGO types and functions

[remorses]

gopls version

Build info
----------
golang.org/x/tools/gopls v0.18.1
    golang.org/x/tools/gopls@v0.18.1 h1:2xJBNzdImS5u/kV/ZzqDLSvlBSeZX+pWY9uKVP7Pask=
    github.com/BurntSushi/toml@v1.4.1-0.20240526193622-a339e1f7089c h1:pxW6RcqyfI9/kWtOwnv/G+AzdKuy2ZrqINhenH4HyNs=
    github.com/google/go-cmp@v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
    golang.org/x/exp/typeparams@v0.0.0-20241210194714-1829a127f884 h1:1xaZTydL5Gsg78QharTwKfA9FY9CZ1VQj6D/AZEvHR0=
    golang.org/x/mod@v0.23.0 h1:Zb7khfcRGKk+kqfxFaP5tZqCnDZMjC5VtUBs87Hr6QM=
    golang.org/x/sync@v0.11.0 h1:GGz8+XQP4FvTTrjZPzNKTMFtSXH80RAzG+5ghFPgK9w=
    golang.org/x/telemetry@v0.0.0-20241220003058-cc96b6e0d3d9 h1:L2k9GUV2TpQKVRGMjN94qfUMgUwOFimSQ6gipyJIjKw=
    golang.org/x/text@v0.22.0 h1:bofq7m3/HAFvbF51jz3Q9wLg3jkvSPuiZu/pD1XwgtM=
    golang.org/x/tools@v0.30.1-0.20250221230316-5055f70f240c h1:Ja/5gV5a9Vvho3p2NC/T2TtxhHjrWS/2DvCKMvA0a+Y=
    golang.org/x/vuln@v1.1.3 h1:NPGnvPOTgnjBc9HTaUx+nj+EaUYxl5SJOWqaDYGaFYw=
    honnef.co/go/tools@v0.5.1 h1:4bH5o3b5ZULQ4UrBmP+63W9r7qIkqJClEA9ko5YKx+I=
    mvdan.cc/gofumpt@v0.7.0 h1:bg91ttqXmi9y2xawvkuMXyvAA/1ZGJqYAEGjXuP0JXU=
    mvdan.cc/xurls/v2@v2.5.0 h1:lyBNOm8Wo71UknhUs4QTFUNNMyxy2JEIaKKo0RWOh+8=
go: go1.24.1

go env

AR='ar'
CC='cc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='c++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/morse/Library/Caches/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/morse/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/8w/wvmrpgms5hngywvs8s99xnmm0000gn/T/go-build841855491=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/dev/null'
GOMODCACHE='/Users/morse/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/morse/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/opt/homebrew/Cellar/go/1.24.1/libexec'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/morse/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/opt/homebrew/Cellar/go/1.24.1/libexec/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.24.1'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

When writing code like this

package main

/*
#cgo pkg-config: mlt-framework-7
#cgo LDFLAGS: -L/usr/local/lib -Wl,-rpath,/usr/local/lib
#include <mlt-7/framework/mlt.h>
#include <stdlib.h>
#cgo LDFLAGS: -lmlt-7
*/
import "C"
import (
	"flag"
	"fmt"
	"unsafe"
)

func makePlaylist(files []string) (pl C.mlt_playlist, profile C.mlt_profile) {
	profile = C. // autocomplete here

What did you see happen?

No autocomplete after writing C.

What did you expect to see?

Add available function and types declared in the C headers as autocomplete suggestion in intellisense

Editor and settings

VSCode with default settings

Logs

No response

[gabyhelp]

Related Issues

• x/tools/gopls: variable autocomplete is not working correctly on broken code #48964 (closed)
• x/tools/gopls: run completion using partial type checking of current package #68063
• x/tools/gopls: Autocompletion implementation should contain comments for the interface. #65543 (closed)
• x/tools/gopls: unimported completion corrupts import decl (client=BBEdit) #70646 (closed)
• x/tools/gopls: completion: missing field completion in multi-LHS assignment "a.C, b.‸" #70065 (closed)
• x/tools/gopls: not working #37119 (closed)
• x/tools/gopls: go.mod: Please provide completions for package versions #58769
• x/tools/gopls: Use source from GOMODCACHE if available even if the dependant module is vendored #52952 (closed)
• x/tools/gopls: Automatic completion of functions using interface annotations #59594
• x/tools/gopls: For generic function completion, don't complete with `Name[|]()` if type parameters can be inferred #72758

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[madelinekalil]

Thank you bringing up this issue! This would certainly be helpful, but is tricky and would require some deeper thinking about how we can make gopls work better for CGO. Added to the backlog

[paskozdilar]

Since CGo is just C in Go's clothing, we could offload the hard work to clangd, and just parse it's output in gopls.
That would also allow us to use .clangd and all its features, which would integrate well with existing C workflows.