Gopls: Code lenses

A “code lens” is a command associated with a range of a source file. The VS Code manual describes code lenses as “actionable, contextual information, interspersed in your source code”. The LSP textDocument/codeLens operation requests the current set of code lenses for a file.

Gopls generates code lenses from a number of sources. This document describes them.

They can be enabled and disabled using the codelenses setting. Their features are subject to change.

Client support:

  • VS Code: Code Lenses appear as small text links above a line of source code.
  • Emacs + eglot: Not supported, but prototype exists at https://github.joaotavora/eglot/pull/71.
  • Vim + coc.nvim: ??
  • CLI: gopls codelens. For example, gopls codelens -exec file.go:123 "run test" runs the test at the specified line.

gc_details: Toggle display of Go compiler optimization decisions

This codelens source causes the package declaration of each file to be annotated with a command to toggle the state of the per-session variable that controls whether optimization decisions from the Go compiler (formerly known as “gc”) should be displayed as diagnostics.

Optimization decisions include:

  • whether a variable escapes, and how escape is inferred;
  • whether a nil-pointer check is implied or eliminated;
  • whether a function can be inlined.

TODO(adonovan): this source is off by default because the annotation is annoying and because VS Code has a separate “Toggle gc details” command. Replace it with a Code Action (“Source action...”).

Default: off

File type: Go

generate: Run go generate

This codelens source annotates any //go:generate comments with commands to run go generate in this directory, on all directories recursively beneath this one.

See Generating code for more details.

Default: on

File type: Go

regenerate_cgo: Re-generate cgo declarations

This codelens source annotates an import "C" declaration with a command to re-run the cgo command to regenerate the corresponding Go declarations.

Use this after editing the C code in comments attached to the import, or in C header files included by it.

Default: on

File type: Go

test: Run tests and benchmarks

This codelens source annotates each Test and Benchmark function in a *_test.go file with a command to run it.

This source is off by default because VS Code has a client-side custom UI for testing, and because progress notifications are not a great UX for streamed test output. See:

Default: off

File type: Go

run_govulncheck: Run govulncheck

This codelens source annotates the module directive in a go.mod file with a command to run Govulncheck.

Govulncheck is a static analysis tool that computes the set of functions reachable within your application, including dependencies; queries a database of known security vulnerabilities; and reports any potential problems it finds.

Default: off

File type: go.mod

tidy: Tidy go.mod file

This codelens source annotates the module directive in a go.mod file with a command to run go mod tidy, which ensures that the go.mod file matches the source code in the module.

Default: on

File type: go.mod

upgrade_dependency: Update dependencies

This codelens source annotates the module directive in a go.mod file with commands to:

  • check for available upgrades,
  • upgrade direct dependencies, and
  • upgrade all dependencies transitively.

Default: on

File type: go.mod

vendor: Update vendor directory

This codelens source annotates the module directive in a go.mod file with a command to run go mod vendor, which creates or updates the directory named vendor in the module root so that it contains an up-to-date copy of all necessary package dependencies.

Default: on

File type: go.mod