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Eglot Features ​

While Eglot is enabled in a buffer, it is said to be managing it, using LSP and the specific capabilities of the language server to activate and enhance modern IDE features in Emacs. Some of these features are provided via other Emacs packages, and some via Eglot directly (see Eglot Commands).

Here’s an overview of the main features that Eglot provides:

  • At-point documentation: when point is near a symbol or an identifier, information about the identifier’s significance in the program (its function or method signature, its type, its custom documentation string, etc.) is made available via the ElDoc package (see Programming Language Doc in GNU Emacs Manual).
  • On-the-fly diagnostic annotations, via the Flymake package (see GNU Flymake manual). Eglot’s Flymake backend replaces other Flymake backends while it is managing a buffer, and enhances diagnostics with interactive server-suggested fixes (so-called code actions, see Eglot Commands).
  • Finding definitions and uses of identifiers, via Xref (see Xref in GNU Emacs Manual). Eglot provides a backend for the Xref capabilities which uses the language server’s understanding of the program source. In particular, it eliminates the need to generate tags tables (see Tags tables in GNU Emacs Manual) for languages which are only supported by the etags backend.
  • Buffer navigation by name of function, class, method, etc., via Imenu (see Imenu in GNU Emacs Manual). Eglot provides its own variant of imenu-create-index-function, which generates the index for the buffer based on the language server’s program source analysis.
  • Enhanced completion of symbol at point by the completion-at-point command (see Symbol Completion in GNU Emacs Manual). This uses the language server’s parser data for the completion candidates.
  • Server-suggested code refactorings. The ElDoc package is also leveraged to retrieve so-called code actions nearby point. When such suggestions are available they are annotated with a special indication and can be easily invoked by the user with the eglot-code-action command (see Eglot Commands).
  • On-the-fly succinct informative annotations, so-called inlay hints. Eglot adds special intangible text nearby certain identifiers, be it the type of a variable, or the name of a formal parameter in a function call. See Eglot Commands, and the eglot-inlay-hints-mode minor mode.
  • Enhanced source code fontification via LSP semantic tokens. Eglot can leverage the language server’s understanding of the role and meaning of identifiers in the code to provide more accurate syntax highlighting. See Eglot Commands, and the eglot-semantic-tokens-mode minor mode.
  • Display of function call and type hierarchies via the eglot-show-call-hierarchy and eglot-show-type-hierarchy commands (see Eglot Commands).
  • Code reformatting via the eglot-format and related commands (see Eglot Commands). Automatic reformatting of source code is also supported and is activated automatically as you type.
  • Eglot enhances symbol completion front-ends by providing completion candidates based on the language server’s understanding of the source code (see Symbol Completion in GNU Emacs Manual). The Company package, installable from GNU ELPA, is a popular package known to work well with Eglot.
  • If YASnippet, a popular third-party package for automatic insertion of code templates (snippets), is installed, and the language server supports snippet completion candidates, Eglot arranges for the completion package to instantiate these snippets using YASnippet. (YASnippet can be installed from GNU ELPA.)
  • When the server provides at-point documentation formatted as Markdown in addition to plain text, Eglot arranges for the ElDoc package to enrich this text with fontifications, hyperlinks and other nice formatting before displaying it to the user. This makes the documentation shown by ElDoc look nicer on display.
  • In addition to enabling and enhancing other features and packages, Eglot also provides a number of user commands based on the capabilities of language servers. Examples include renaming symbols with eglot-rename and asking to automatically correct problems with eglot-code-actions. See Eglot Commands.

Not all servers support the full set of LSP capabilities, but most of them support enough to enable the basic set of features mentioned above.

Conversely, some servers offer capabilities for which no equivalent Emacs package exists yet, and so Eglot cannot (yet) expose these capabilities to Emacs users. However, See Extending Eglot.

Finally, it’s worth noting that, by default, Eglot generally turns on all features that it can turn on. It’s possible to opt out of features via the eglot-ignored-server-capabilities user option (see Customizing Eglot) and the eglot-managed-mode-hook hook that runs after Eglot starts managing a buffer (see Buffers, Projects, and Eglot).