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fix(:tools lsp): make eglot diags use flycheck with :checkers syntax

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Research on how Flycheck work, and a pending fix from Eglot, allowed to
get a cleaner representation of how this "hack" works and make it more
resilient

Co-Authored-By: Steve Purcell <steve@sanityinc.com>
This commit is contained in:
Gerry Agbobada 2021-04-14 09:09:37 +02:00
parent 539ab8d1e9
commit 813dc6e664
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GPG key ID: BE26DBAFD866BE34
2 changed files with 26 additions and 20 deletions
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44
modules/tools/lsp/autoload/flycheck-eglot.el
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@ -1,22 +1,27 @@
;;; flycheck-eglot --- Hacky eglot support in flycheck -*- lexical-binding: t; -*-
;;; Commentary:
;; This file sets up flycheck so that, when eglot receives a publishDiagnostics method
;; from the server, then eglot calls a report function that creates diagnostics for
;; flycheck.
;; from the server, flycheck updates the reports.
;;
;; It works by creating an eglot-specific callback function, and using this as
;; the REPORT-FN argument of `eglot-flymake-backend', which internally registers
;; that lambda as the function to use whenever there is a publishDiagnostics method.
;; Calling `+lsp--flycheck-eglot-init' "too late" is not a problem, since if there
;; are any unreported/missed diagnostics, eglot ensures that the
;; REPORT-FN function is called immediately.
;; Thanks to:
;; - joaotavora for adding a handle to plug flycheck, and
;; - purcell for finding out the initial stub and the current implementation
;;
;; It works by creating a bridge function which can be used as the argument of
;; `eglot-flymake-backend', which both consumes diagnostics and queue a call to
;; 'flycheck-buffer'
;;
;; Note: as long as joaotavora/eglot#596 isn't fixed/dealt with, this checker cannot
;; work. Please check the issue on github for more context
;;; Code:
(defvar-local +lsp--flycheck-eglot--current-errors nil)
(defun +lsp--flycheck-eglot-init (checker callback)
"CHECKER is the checker (eglot).
CALLBACK is the function that we need to call when we are done, on all the errors."
(eglot-flymake-backend #'+lsp--flycheck-eglot--on-diagnostics)
(funcall callback 'finished +lsp--flycheck-eglot--current-errors))
(defun +lsp--flycheck-eglot--on-diagnostics (diags &rest _)
(cl-labels
((flymake-diag->flycheck-err
(diag)
@ -30,17 +35,13 @@ CALLBACK is the function that we need to call when we are done, on all the error
(_ (error "Unknown diagnostic type, %S" diag)))
(flymake--diag-text diag)
:end-pos (flymake--diag-end diag)
:checker checker
:checker 'eglot
:buffer (current-buffer)
:filename (buffer-file-name)))))
;; NOTE: Setting up eglot to automatically create flycheck errors for the buffer.
;; Internally, this sets the lambda as the callback to be used by eglot
;; when it receives a publishDiagnostics method from the server
(eglot-flymake-backend
(lambda (flymake-diags &rest _)
(funcall callback
'finished
(mapcar #'flymake-diag->flycheck-err flymake-diags))))))
(setq +lsp--flycheck-eglot--current-errors
(mapcar #'flymake-diag->flycheck-err diags))
;; Call Flycheck to update the diagnostics annotations
(flycheck-buffer-deferred)))
(defun +lsp--flycheck-eglot-available-p ()
(bound-and-true-p eglot--managed-mode))
@ -56,11 +57,14 @@ CALLBACK is the function that we need to call when we are done, on all the error
(add-hook! 'eglot-managed-mode-hook
(defun +lsp-eglot-prefer-flycheck-h ()
(when eglot--managed-mode
(flymake-mode -1)
(when-let ((current-checker (flycheck-get-checker-for-buffer)))
(unless (equal current-checker 'eglot)
(flycheck-add-next-checker 'eglot current-checker)))
(flycheck-add-mode 'eglot major-mode)
(flycheck-mode 1)
(flymake-mode -1))))
;; Call flycheck on initilization to make sure to display initial
;; errors
(flycheck-buffer-deferred))))
;;; flycheck-eglot.el ends here