gopls/doc/release/v0.21.0.md - tools - Git at Google

 ---
 title: "Gopls release v0.21.0 (Dec 2025)"
 ---

 ## Configuration changes

 - The new `newGoFileHeader` option allows toggling automatic insertion of the copyright comment
   and package declaration in a newly created Go file.

 - The default value of the `codelenses` setting now includes
   `run_govulncheck: true`, causing gopls to offer a "Run govulncheck"
   command associated with the `module` declaration in a go.mod file.

 - The experimental `vulncheck` setting now supports the enum value
   `"Prompt"`, meaning that vulncheck can be triggered via a prompt;
   this is now the default.

 - The new, experimental `renameMovesSubpackages` setting determines
   whether a rename package operation applies to subdirectories; see
   below for details.

 ## Navigational features:

 Hover can now report information about selected subexpressions (#69058).
 For example, selecting the region indicated below:

 	 x[i].f()
 	 ~~~~

 will report information about the subexpression `x[i]`, such as its
 type, constant value (if appropriate), and methods.
 Previously, Hover would report only about `x`, `i`, or `f`.

 This feature requires the client to supply an extra field in the
 `textDocumentPositionParams` part of its LSP `textDocument/hover`
 request: the standard struct has a single `position` of type
 `Position`, but gopls can also handle a `range` field of type
 `Range` that specifies the extent of the text selection.
 (If supplied, it must enclose the `position`.)

 The VS Code code extension already populates this field. We plan to
 use it across various requests, and to lobby for its adoption by the
 LSP standard.

 Other features in brief:

 - Definition now works for fields in doc links in comments (#75038).
 - Hover adds navigation to doc links in hovers (golang/vscode-go#3827).
 - Hover now reports information (size, etc) about embedded fields, not just their types (#75975).
 - Folding Range now displays closing parens (#75229) and more ranges (#73735).

 ## Analysis features

 ### `reflecttypefor` analyzer

 <!-- golang/go#60088 -->

 The new `reflecttypefor` analyzer modernizes calls to `reflect.TypeOf`
 to use `reflect.TypeFor` when the runtime type is known at compile
 time. For example:

 	reflect.TypeOf(uint32(0))

 becomes:

 	reflect.TypeFor[uint32]()

 ### `newexpr` analyzer

 <!-- golang/go#45624 -->

 The `newexpr` analyzer finds declarations of and calls to functions
 of this form:
 ```go
 func varOf(x int) *int { return &x }

 use(varOf(123))
 ```
 modernizing them when appropriate to use the `new(expr)` feature of Go 1.26:
 ```go
 //go:fix inline
 func varOf(x int) *int { return new(x) }

 use(new(123))
 ```

 Such wrapper functions are widely used in serialization packages,
 for instance the proto.{Int64,String,Bool} helpers used with
 protobufs.

 ### `stditerators` analyzer

 <!-- golang/go#75693 -->

 The `stditerators` analyzer replaces loops of this form,

       for i := 0; i < x.Len(); i++ {
           use(x.At(i))
       }

 or their "range x.Len()" equivalent, by

       for elem := range x.All() {
           use(elem)
       }

 for various types in the standard library that now offer a
 modern iterator-based API.

 ### `stringscut` analyzer

 <!-- golang/go#71369 -->

 The `stringscut` analyzer modernizes various patterns of use of
 `strings.Index` such as:

 	i := strings.Index(s, sep)
 	if i >= 0 {
 		use(s[i:])
 	}

 by a call to `strings.Cut`, introduced in Go 1.25:

 	before, after, ok := strings.Cut(s, sep)
 	if ok {
 		use(after)
 	}

 ### `plusbuild` analyzer

 <!-- golang/go#73605 -->

 The `plusbuild` analyzer removes old-style `+build` build-tag comments
 when they are redundant with the newer form:

 	//go:build linux
 	// +build linux

 ### `errorsastype` analyzer

 <!-- golang/go#75692 -->

 The `errorsastype` analyzer replaces calls to `errors.As`:

 	var myErr *MyError
 	if errors.As(err, &myErr) { ... }

 by the more modern `errors.AsType`, when the type is known statically:

 	if myErr, ok := errors.AsType[*MyError](err) { ... }


 ### `unsafefuncs` analyzer

 <!-- golang/go#76648 -->

 The `unsafefuncs` analyzer replaces arithmetic such as:

 	unsafe.Pointer(uintptr(ptr) + uintptr(n))

 where ptr is an unsafe.Pointer, by calls to `unsafe.Add`, added in Go 1.17.

 	unsafe.Add(ptr, n)

 ### Miscellaneous

 - The `minmax` modernizer now removes user-defined min/max functions when they are redundant.
 - The `stringscutprefix` modernizer now handles `strings.CutSuffix` too. <!-- #75205 -->
 - The `yield` and `nilness` analyzers handle control-flow booleans more precisely. <!-- #74136, #75924 -->
 - The `printf` analyzer now checks calls to local anonymous printf-wrapper functions too.
 - The `staticcheck` suite has been updated to v0.7.

 ## Code transformation features

 ### Generalized package renaming

 <!-- #57171 #75812 -->

 The Rename operation, invoked on a `package p` declaration, now
 prompts you to edit the entire package path. This allows you to choose
 not just a new name for the package, but a new directory anywhere
 within the same module. For example, you can rename `example.com/foo`
 to `example.com/internal/bar`, and the tool will move files and update
 imports as needed.

 By default, subpackages are no longer moved with the renamed package.
 Enable the new (experimental) `renameMovesSubpackages` setting if you
 want subpackages to move too. (In due course, we will add LSP support
 for dialogs so that the server can query the user's intent
 interactively.)

 This feature requires client support for the LSP
 [`textDocument/prepareRename`](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_prepareRename) operation.

 ### Renaming from a doc link

 <!-- golang/go#42301 -->
 The Rename operation now treats [doc links](https://tip.golang.org/doc/comment#doclinks)
 like identifiers, so you can initiate a renaming from a doc link.

 ## Model context protocol (MCP) features

 The MCP server now supports the `go_rename_symbol` tool, which permits
 an agent to rename a symbol based on its name (e.g. `fmt.Println` or
 `bytes.Buffer.WriteString`). The tool uses the symbol index to resolve
 the name to a declaration and then initiates a renaming.

 The server also supports the `gopls.vulncheck` tool, allowing agents
 to scan packages for security vulnerabilities.

 ## Closed issues

 https://github.com/golang/go/milestone/399?closed=1
	---
	title: "Gopls release v0.21.0 (Dec 2025)"
	---

	## Configuration changes

	- The new `newGoFileHeader` option allows toggling automatic insertion of the copyright comment
	and package declaration in a newly created Go file.

	- The default value of the `codelenses` setting now includes
	`run_govulncheck: true`, causing gopls to offer a "Run govulncheck"
	command associated with the `module` declaration in a go.mod file.

	- The experimental `vulncheck` setting now supports the enum value
	`"Prompt"`, meaning that vulncheck can be triggered via a prompt;
	this is now the default.

	- The new, experimental `renameMovesSubpackages` setting determines
	whether a rename package operation applies to subdirectories; see
	below for details.

	## Navigational features:

	Hover can now report information about selected subexpressions (#69058).
	For example, selecting the region indicated below:

	x[i].f()
	~~~~

	will report information about the subexpression `x[i]`, such as its
	type, constant value (if appropriate), and methods.
	Previously, Hover would report only about `x`, `i`, or `f`.

	This feature requires the client to supply an extra field in the
	`textDocumentPositionParams` part of its LSP `textDocument/hover`
	request: the standard struct has a single `position` of type
	`Position`, but gopls can also handle a `range` field of type
	`Range` that specifies the extent of the text selection.
	(If supplied, it must enclose the `position`.)

	The VS Code code extension already populates this field. We plan to
	use it across various requests, and to lobby for its adoption by the
	LSP standard.

	Other features in brief:

	- Definition now works for fields in doc links in comments (#75038).
	- Hover adds navigation to doc links in hovers (golang/vscode-go#3827).
	- Hover now reports information (size, etc) about embedded fields, not just their types (#75975).
	- Folding Range now displays closing parens (#75229) and more ranges (#73735).

	## Analysis features

	### `reflecttypefor` analyzer

	<!-- golang/go#60088 -->

	The new `reflecttypefor` analyzer modernizes calls to `reflect.TypeOf`
	to use `reflect.TypeFor` when the runtime type is known at compile
	time. For example:

	reflect.TypeOf(uint32(0))

	becomes:

	reflect.TypeFor[uint32]()

	### `newexpr` analyzer

	<!-- golang/go#45624 -->

	The `newexpr` analyzer finds declarations of and calls to functions
	of this form:
	```go
	func varOf(x int) *int { return &x }

	use(varOf(123))
	```
	modernizing them when appropriate to use the `new(expr)` feature of Go 1.26:
	```go
	//go:fix inline
	func varOf(x int) *int { return new(x) }

	use(new(123))
	```

	Such wrapper functions are widely used in serialization packages,
	for instance the proto.{Int64,String,Bool} helpers used with
	protobufs.

	### `stditerators` analyzer

	<!-- golang/go#75693 -->

	The `stditerators` analyzer replaces loops of this form,

	for i := 0; i < x.Len(); i++ {
	use(x.At(i))
	}

	or their "range x.Len()" equivalent, by

	for elem := range x.All() {
	use(elem)
	}

	for various types in the standard library that now offer a
	modern iterator-based API.

	### `stringscut` analyzer

	<!-- golang/go#71369 -->

	The `stringscut` analyzer modernizes various patterns of use of
	`strings.Index` such as:

	i := strings.Index(s, sep)
	if i >= 0 {
	use(s[i:])
	}

	by a call to `strings.Cut`, introduced in Go 1.25:

	before, after, ok := strings.Cut(s, sep)
	if ok {
	use(after)
	}

	### `plusbuild` analyzer

	<!-- golang/go#73605 -->

	The `plusbuild` analyzer removes old-style `+build` build-tag comments
	when they are redundant with the newer form:

	//go:build linux
	// +build linux

	### `errorsastype` analyzer

	<!-- golang/go#75692 -->

	The `errorsastype` analyzer replaces calls to `errors.As`:

	var myErr *MyError
	if errors.As(err, &myErr) { ... }

	by the more modern `errors.AsType`, when the type is known statically:

	if myErr, ok := errors.AsType[*MyError](err) { ... }


	### `unsafefuncs` analyzer

	<!-- golang/go#76648 -->

	The `unsafefuncs` analyzer replaces arithmetic such as:

	unsafe.Pointer(uintptr(ptr) + uintptr(n))

	where ptr is an unsafe.Pointer, by calls to `unsafe.Add`, added in Go 1.17.

	unsafe.Add(ptr, n)

	### Miscellaneous

	- The `minmax` modernizer now removes user-defined min/max functions when they are redundant.
	- The `stringscutprefix` modernizer now handles `strings.CutSuffix` too. <!-- #75205 -->
	- The `yield` and `nilness` analyzers handle control-flow booleans more precisely. <!-- #74136, #75924 -->
	- The `printf` analyzer now checks calls to local anonymous printf-wrapper functions too.
	- The `staticcheck` suite has been updated to v0.7.

	## Code transformation features

	### Generalized package renaming

	<!-- #57171 #75812 -->

	The Rename operation, invoked on a `package p` declaration, now
	prompts you to edit the entire package path. This allows you to choose
	not just a new name for the package, but a new directory anywhere
	within the same module. For example, you can rename `example.com/foo`
	to `example.com/internal/bar`, and the tool will move files and update
	imports as needed.

	By default, subpackages are no longer moved with the renamed package.
	Enable the new (experimental) `renameMovesSubpackages` setting if you
	want subpackages to move too. (In due course, we will add LSP support
	for dialogs so that the server can query the user's intent
	interactively.)

	This feature requires client support for the LSP
	[`textDocument/prepareRename`](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_prepareRename) operation.

	### Renaming from a doc link

	<!-- golang/go#42301 -->
	The Rename operation now treats [doc links](https://tip.golang.org/doc/comment#doclinks)
	like identifiers, so you can initiate a renaming from a doc link.

	## Model context protocol (MCP) features

	The MCP server now supports the `go_rename_symbol` tool, which permits
	an agent to rename a symbol based on its name (e.g. `fmt.Println` or
	`bytes.Buffer.WriteString`). The tool uses the symbol index to resolve
	the name to a declaration and then initiates a renaming.

	The server also supports the `gopls.vulncheck` tool, allowing agents
	to scan packages for security vulnerabilities.

	## Closed issues

	https://github.com/golang/go/milestone/399?closed=1