gopls/v0.16.0

go install golang.org/x/tools/gopls@v0.16.0

Configuration Changes

• The default value of the “semanticTokens” setting is now “true”. This means that if your LSP client is able and configured to request semantic tokens, gopls will provide them. The default was previously false because VS Code historically provided no client-side way for users to disable the feature.
• The experimental “allowImplicitNetworkAccess” setting is deprecated (but not yet removed). Please comment on https://go.dev/issue/66861 if you use this setting and would be impacted by its removal.

New features

Integrated documentation viewer

Gopls now offers a “View package documentation” code action that opens a local web page displaying the generated documentation for the current Go package in a form similar to https://pkg.go.dev. The page will be initially scrolled to the documentation for the declaration containing the cursor. Use this feature to preview the marked-up documentation as you prepare API changes, or to read the documentation for locally edited packages, even ones that have not yet been saved. Reload the page after an edit to see updated documentation.

TODO: demo in VS Code.

Clicking on the source-code link associated with a declaration will cause your editor to navigate to the declaration.

TODO: demo of source linking.

Editor support:

• VS Code: use the Source action > View package documentation menu item. Note: source links navigate the editor but don't yet raise the window yet. Please upvote https://github.com/microsoft/vscode/issues/208093 and https://github.com/microsoft/vscode/issues/207634 (temporarily closed).

• Emacs: requires eglot v1.17. You may find this go-doc function a useful shortcut:

(eglot--code-action eglot-code-action-doc "source.doc")

(defalias 'go-doc #'eglot-code-action-doc
  "View documentation for the current Go package.")

• TODO: test in vim, neovim, sublime, helix.

unusedwrite analyzer

The new unusedwrite analyzer reports assignments, often to fields of structs, that have no effect because, for example, the struct is never used again:

func scheme(host string) string {
	u := &url.URL{
		Host:   host, // "unused write to field Host" (no need to construct a URL)
		Scheme: "https:",
	}
	return u.Scheme
}

This is at best an indication that the code is unnecessarily complex (for instance, some dead code could be removed), but often indicates a bug, as in this example:

type S struct { x int }

func (s S) set(x int) {
	s.x = x // "unused write to field x" (s should be a *S pointer)
}

Hover shows size/offset info

Hovering over the identifier that declares a type or struct field now displays the size information for the type, and the offset information for the field. In addition, it reports the percentage of wasted space due to suboptimal ordering of struct fields, if this figure is 20% or higher. This information may be helpful when making space optimizations to your data structures, or when reading assembly code.

TODO: example hover image.

Hover and definition on doc links

Go 1.19 added support for links in doc comments, allowing the documentation for one symbol to reference another:

TODO: turn the code below into a VS Code screenshot of hover.

// Logf logs a message formatted in the manner of [fmt.Printf].
func Logf(format string, args ...any)

Gopls's Hover and Definition operations now treat these links just like identifiers, so hovering over one will display information about the symbol, and “Go to definition” will navigate to its declaration. Thanks to @rogeryk for contributing this feature.

Bugs fixed

Thank you to our contributors!

@guodongli-google for the unusedwrite analyzer. TODO: they're a xoogler; is there a more current GH account?

@rogeryk