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Gopls: Navigation features

This page documents gopls features for navigating your source code.

Definition

The LSP textDocument/definition request returns the location of the declaration of the symbol under the cursor. Most editors provide a command to navigate directly to that location.

A definition query also works in these unexpected places:

  • On an import path, it returns the list of locations, of each package declaration in the files of the imported package.
  • On a package declaration, it returns the location of the package declaration that provides the documentation of that package.
  • On a symbol in a go:linkname directive, it returns the location of that symbol's declaration.
  • On a doc link, it returns (like hover) the location of the linked symbol.
  • On a file name in a go:embed directive, it returns the location of the embedded file.
  • On the declaration of a non-Go function (a func with no body), it returns the location of the assembly implementation, if any,
  • On a return statement, it returns the location of the function's result variables.
  • On a goto, break, or continue statement, it returns the location of the label, the closing brace of the relevant block statement, or the start of the relevant loop, respectively.

Client support:

  • VS Code: Use Go to Definition (F12 or ⌘-click). If the cursor is already at the declaration, the request is instead interpreted as "Go to References".
  • Emacs + eglot: use M-x xref-find-definitions.
  • Vim + coc.nvim: ??
  • CLI: gopls definition file.go:#offset

References

The LSP textDocument/references request returns the locations of all identifiers that refer to the symbol under the cursor.

The references algorithm handles various parts of syntax as follows:

  • The references to a symbol report all uses of that symbol. In the case of exported symbols this may include locations in other packages.
  • The references to a package declaration are all the direct imports of the package, along with all the other package declarations in the same package.
  • It is an error to request the references to a built-in symbol such as int or append, as they are presumed too numerous to be of interest.
  • The references to an interface method include references to concrete types that implement the interface. Similarly, the references to a method of a concrete type include references to corresponding interface methods.
  • An embedded field T in a struct type such as struct{T} is unique in Go in that it is both a reference (to a type) and a definition (of a field). The references operation reports only the references to it as a field. To find references to the type, jump to the type declararation first.

Be aware that a references query returns information only about the build configuration used to analyze the selected file, so if you ask for the references to a symbol defined in foo_windows.go, the result will never include the file bar_linux.go, even if that file refers to a symbol of the same name; see golang/go#65755.

Clients can request that the the declaration be included among the references; most do.

Client support:

  • VS Code: Use Go to References to quickly "peek" at the references, or Find all References to open the references panel.
  • Emacs + eglot: Via xref package: use M-x xref-find-references.
  • Vim + coc.nvim: ??
  • CLI: gopls references file.go:#offset

Implementation

The LSP textDocument/implementation request queries the "implements" relation between interfaces and concrete types:

  • When invoked on a reference to an interface type, it returns the location of the declaration of each type that implements the interface.
  • When invoked on a concrete type, it returns the locations of the matching interface types.
  • When invoked on an interface method, it returns the corresponding methods of the types that satisfy the interface.
  • When invoked on a concrete method, it returns the locations of the matching interface methods.

Only non-trivial interfaces are considered; no implementations are reported for type any.

Within the same package, all matching types/methods are reported. However, across packages, only exported package-level types and their methods are reported, so local types (whether interfaces, or struct types with methods due to embedding) may be missing from the results.

If either the target type or the candidate type are generic, the results will include the candidate type if there is any instantiation of the two types that would allow one to implement the other. (Note: the matcher doesn't current implement full unification, so type parameters are treated like wildcards that may match arbitrary types, without regard to consistency of substitutions across the method set or even within a single method. This may lead to occasional spurious matches.)

Client support:

  • VS Code: Use Go to Implementations (⌘F12).
  • Emacs + eglot: Use M-x eglot-find-implementation.
  • Vim + coc.nvim: ??
  • CLI: gopls implementation file.go:#offset

Type Definition

The LSP textDocument/typeDefinition request returns the location of the type of the selected symbol.

For example, if the selection is the name buf of a local variable of type *bytes.Buffer, a typeDefinition query will return the location of the type bytes.Buffer. Clients typically navigate to that location.

Type constructors such as pointer, array, slice, channel, and map are stripped off the selected type in the search for a named type. For example, if x is of type chan []*T, the reported type definition will be that of T. Similarly, if the symbol's type is a function with one "interesting" (named, non-error) result type, the function's result type is used.

Gopls currently requires that a typeDefinition query be applied to a symbol, not to an arbitrary expression; see golang/go#67890 for potential extensions of this functionality.

Client support:

  • VS Code: Use Go to Type Definition.
  • Emacs + eglot: Use M-x eglot-find-typeDefinition.
  • Vim + coc.nvim: ??
  • CLI: not supported

Document Symbol

The textDocument/documentSymbol LSP query reports the list of top-level declarations in this file. Clients may use this information to present an overview of the file, and an index for faster navigation.

Gopls responds with the DocumentSymbol type if the client indicates hierarchicalDocumentSymbolSupport; otherwise it returns a SymbolInformation.

Client support:

  • VS Code: Use the Outline view for navigation.
  • Emacs + eglot: Use M-x imenu to jump to a symbol.
  • Vim + coc.nvim: ??
  • CLI: gopls links file.go

Symbol

The workspace/symbol LSP query searches an index of all the symbols in the workspace.

The default symbol matching algorithm (fastFuzzy), inspired by the popular fuzzy matcher FZF, attempts a variety of inexact matches to correct for misspellings or abbreviations in your query. For example, it considers DocSym a match for DocumentSymbol.

Settings:

  • The symbolMatcher setting controls the algorithm used for symbol matching.
  • The symbolStyle setting controls how symbols are qualified in symbol responses.
  • The symbolScope setting determines the scope of the query.
  • The directoryFilters setting specifies directories to be excluded from the search.

Client support:

  • VS Code: Use ⌘T to open Go to Symbol with workspace scope. (Alternatively, use Ctrl-Shift-O, and add a @ prefix to search within the file or a # prefix to search throughout the workspace.)
  • Emacs + eglot: Use M-x xref-find-apropos to show symbols that match a search term.
  • Vim + coc.nvim: ??
  • CLI: gopls links file.go

Selection Range

The textDocument/selectionRange LSP query returns information about the lexical extent of each piece of syntax enclosing the current selection. Clients may use it to provide an operation to expand the selection to successively larger expressions.

Client support:

  • VSCode: Use ⌘⇧^→ to expand the selection or ⌘⇧^← to contract it again; watch this video.
  • Emacs + eglot: Not standard. Use M-x eglot-expand-selection defined in this configuration snippet.
  • Vim + coc.nvim: ??
  • CLI: not supported

Call Hierarchy

The LSP CallHierarchy mechanism consists of three queries that together enable clients to present a hierarchical view of a portion of the static call graph:

Invoke the command while selecting the name in a function declaration.

Dynamic calls are not included, because it is not analytically practical to detect them. So, beware that the results may not be exhaustive, and perform a References query if necessary.

The hierarchy does not consider a nested function distinct from its enclosing named function. (Without the ability to detect dynamic calls, it would make little sense do so.)

The screenshot below shows the outgoing call tree rooted at f. The tree has been expanded to show a path from f to the String method of fmt.Stringer through the guts of fmt.Sprint:

Caveats:

  • In some cases dynamic function calls are (erroneously) included in the output; see golang/go#68153.

Client support:

  • VS Code: Show Call Hierarchy menu item (⌥⇧H) opens Call hierarchy view (note: docs refer to C++ but the idea is the same for Go).
  • Emacs + eglot: Not standard; install with (package-vc-install "https://github.com/dolmens/eglot-hierarchy"). Use M-x eglot-hierarchy-call-hierarchy to show the direct incoming calls to the selected function; use a prefix argument (C-u) to show the direct outgoing calls. There is no way to expand the tree.
  • CLI: gopls call_hierarchy file.go:#offset shows outgoing and incoming calls.