golang/tools gopls/v0.15.0

on GitHub

These release notes are mostly identical to the v0.15.0-pre.3 prerelease notes. Thanks to all who tested the prerelease!

go install golang.org/x/tools/gopls@v0.15.0

This release introduces "zero config" gopls workspaces, which is a set of heuristics allowing gopls to Do The Right Thing when you open a Go file. We believe this addresses two of the largest pain points we hear about from our users: difficulty configuring multi-module repositories, and working on multiple GOOS/GOARCH combinations. However, this is a large change to the way gopls models your workspace, and the dynamic loading/unloading of builds may be surprising in some cases. Your feedback on this new feature is greatly appreciated. See below for more details.

New Features

Simpler workspace configuration and improved build tag support

The headline feature of this release is a rewrite of gopls's logic for associating files with build configurations that enables gopls to give accurate answers when navigating almost any Go source file on your machine.

Most features of gopls rely on type information, which comes not from the file in isolation but depends on the relationship between the file and the other files in its package, and between the package and all its dependencies; this in turn depends on go.mod and go.work files. In effect, gopls needs to decide which go build command--which working directory, package arguments, GOOS, GOARCH, build tags, and so on--would cause each file to be processed by the compiler.

Previous versions of gopls only allowed one build per workspace folder, and users had to be careful to configure the right workspace root and build environment. As a result, users often encountered confusing error messages when they opened the wrong directory, or a file that was tagged for a different operating system or architecture--the dreaded "No packages found" error. This situation was improved by the introduction of go.work files, but still required configuration and a preexisting understanding of the code being edited.

With this release, gopls now allows multiple builds per workspace, and uses heuristics to automatically derive the set of active builds. Gopls will ensure that an active build contains every module with an open file in your workspace, adding new builds and GOOS/GOARCH combinations as needed to cover files that don't match the host operating system or architecture.

For example, suppose we had a repository with three modules: moda, modb, and modc, and a go.work file using modules moda and modb. If we open the files moda/a.go, modb/b.go, moda/a_windows.go, and modc/c.go, gopls will automatically create three builds:

This allows gopls to just work when you open a Go file, but it does come with several caveats:

• This causes gopls to do more work, since it is now tracking three builds instead of one. However, the recent scalability redesign allows much of this work to be avoided through efficient caching.
• For operations invoked from a given file, such as "References" and "Implementations", gopls executes the operation in the default build for that file. For example, finding references to a symbol S from foo_linux.go will return references from the Linux build, and finding references to the same symbol S from foo_windows.go will return references from the Windows build. Gopls searches the default build for the file, but it doesn't search all the other possible builds because it is liable to be too expensive. golang/go#65757 and golang/go#65755 propose improvements to this behavior.
• When selecting a GOOS/GOARCH combination to match a build-constrained file, gopls will choose the first matching combination from this list. In some cases, that may be surprising.
• When working in a GOOS/GOARCH constrained file that does not match your default toolchain, CGO_ENABLED=0 is implicitly set, since a C toolchain for that target is unlikely to be available. This means that gopls will not work in files including import "C". golang/go#65758 may lead to improvements in this behavior.
• Gopls is currently unable to guess build flags that include arbitrary user-defined build constraints. For example, if you are trying to work on a file that is constrained by the build directive //go:build special, gopls will not guess that it needs to create a build with "buildFlags": ["-tags=special"]. golang/go#65089 proposes a heuristic by which gopls could handle this automatically.

Please provide feedback on this behavior by upvoting or commenting the issues mentioned above, or opening a new issue for other improvements you'd like to see.

Preview refactoring edits

Refactoring code actions now support resolving edits. This update enables features like code action previews within VS Code (triggered by Ctrl+Enter).

To take advantage of this new gopls feature, clients must register support via:

{
	"textDocument": {
		"codeAction": {
			"dataSupport": true,
			"resolveSupport": {
				"properties": ["edit"]
			}
		}
	}
}

Analysis & diagnostics

This release includes two new analyzers:

• The nilness analyzer reports mistakes relating to nil pointers. (In previous releases it was off by default because it was too computationally expensive, but it has since been optimized.)

• The unusedparams analyzer reports when a parameter is unused, and offers quick fixes to either rename it to _ or to remove it completely and update all callers. (This analyzer was also previously off by default because it was too imprecise, but it has been rewritten to eliminate nearly all false positives.)

Automated crash reporting (off by default)

The v1.23 release of Go expected in August contains a feature that makes it possible for a Go program to monitor itself for unexpected crashes of any kind. When gopls is built with the latest Go toolchain, it will enable this feature and save crash reports into the local telemetry database.

If you have elected to enable data collection by running this command:

$ go run golang.org/x/telemetry/cmd/gotelemetry@latest on

then these crash reports will be uploaded to https://telemetry.go.dev, helping us identify crashes and quickly fix them.

We respect your privacy. The crash reports contain only stack traces, that is, lists of names of functions from the gopls source code. They do not contain any values derived from your source code or environment.

The v0.14 release of gopls reported limited telemetry data about a handful of sites in the code where we had added explicit assertions. We are grateful to users who enabled telemetry as even this limited data proved tremendously valuable and led to numerous bug fixes.

Housekeeping

Finishing up the redesign work from v0.12, we've made a number of clarifications to the internal structure of the project, including rationalizing the directory layout, breaking dependencies, minimizing and documenting our internal APIs, and converging our tests on a standard form. We believe it is now easier than ever before to contribute features to gopls, and have been heartened by an uptick in contributions from the broader community, including:

• improved postfix completion (golang/go#64178, golang/go#64037, golang/go#59689);
• improved completion of return statements (golang/go#64266);
• a new code action (refactoring) for conversion between raw and interpreted string literals (golang/go#51200);
• updating of doc links when renaming a symbol (golang/go#64495);
• semantic highlighting for go: directives (golang/go#63538)

Bug fixes

In addition to the new features listed above, this release includes numerous minor ones, including:

• The "add missing imports" feature (typically invoked on save) is much less likely to block, a commonly reported source of freezing following a save (golang/go#59216).
• Hovering over a type now displays the set of accessible fields and methods, even though embedded fields (golang/go#61634).
• gopls supports "workspace vendoring" (golang/go#63375).
• Completion now substitutes type arguments in generic snippets when they are known (golang/go#61189).
• Completion now omits type parameters when they can be inferred from the arguments (golang/go#51783).

A major theme for this release is stability: we have fixed a large number of crash bugs.

A full list of all issues fixed can be found in the gopls/v0.15.0 milestone.
To report a new problem, please file a new issue at https://go.dev/issues/new.

End of support for Go 1.18

This is the last release of gopls that may be built and used with Go 1.18. If built or used with Go 1.18, it will display a message advising the user to upgrade. See supported Go versions for details.

Thank you to our contributors!

@achenet, @adonovan, @bcmills, @Deiz, @hyangah, @pjweinb, @qiulaidongfeng, @qmuntal, @rogeryk, @stapelberg, @suzmue, @timothy-king, @tttoad, @vikblom, @zpavlinovic