;;; rust-compile.el --- Compile facilities           -*-lexical-binding: t-*-
;;; Commentary:

;; This library teaches `compilation-mode' about "rustc" output.

;;; Code:

(require 'compile)

;;; _

(defvar rustc-compilation-location
  (let ((file "\\([^\n]+\\)")
        (start-line "\\([0-9]+\\)")
        (start-col "\\([0-9]+\\)"))
    (concat "\\(" file ":" start-line ":" start-col "\\)")))

(defvar rustc-compilation-regexps
  (let ((re (concat "^\\(?:error\\|\\(warning\\)\\|\\(note\\)\\)[^\0]+?--> "
                    rustc-compilation-location)))
    (cons re '(4 5 6 (1 . 2) 3)))
  "Specifications for matching errors in rustc invocations.
See `compilation-error-regexp-alist' for help on their format.")

(defvar rustc-colon-compilation-regexps
  (let ((re (concat "^ *::: " rustc-compilation-location)))
    (cons re '(2 3 4 0 1)))
  "Specifications for matching `:::` hints in rustc invocations.
See `compilation-error-regexp-alist' for help on their format.")

(defvar rustc-refs-compilation-regexps
  (let ((re "^\\([0-9]+\\)[[:space:]]*|"))
    (cons re '(nil 1 nil 0 1)))
  "Specifications for matching code references in rustc invocations.
See `compilation-error-regexp-alist' for help on their format.")

;; Match test run failures and panics during compilation as
;; compilation warnings
(defvar cargo-compilation-regexps
  '("', \\(\\([^:]+\\):\\([0-9]+\\)\\)"
    2 3 nil nil 1)
  "Specifications for matching panics in cargo test invocations.
See `compilation-error-regexp-alist' for help on their format.")

(defun rustc-scroll-down-after-next-error ()
  "In the new style error messages, the regular expression
matches on the file name (which appears after `-->`), but the
start of the error appears a few lines earlier.  This hook runs
after `next-error' (\\[next-error]); it simply scrolls down a few lines in
the compilation window until the top of the error is visible."
  (save-selected-window
    (when (eq major-mode 'rust-mode)
      (select-window (get-buffer-window next-error-last-buffer 'visible))
      (when (save-excursion
              (beginning-of-line)
              (looking-at " *-->"))
        (let ((start-of-error
               (save-excursion
                 (beginning-of-line)
                 (while (not (looking-at "^[a-z]+:\\|^[a-z]+\\[E[0-9]+\\]:"))
                   (forward-line -1))
                 (point))))
          (set-window-start (selected-window) start-of-error))))))

(eval-after-load 'compile
  '(progn
     (add-to-list 'compilation-error-regexp-alist-alist
                  (cons 'rustc-refs rustc-refs-compilation-regexps))
     (add-to-list 'compilation-error-regexp-alist 'rustc-refs)
     (add-to-list 'compilation-error-regexp-alist-alist
                  (cons 'rustc rustc-compilation-regexps))
     (add-to-list 'compilation-error-regexp-alist 'rustc)
     (add-to-list 'compilation-error-regexp-alist-alist
                  (cons 'rustc-colon rustc-colon-compilation-regexps))
     (add-to-list 'compilation-error-regexp-alist 'rustc-colon)
     (add-to-list 'compilation-error-regexp-alist-alist
                  (cons 'cargo cargo-compilation-regexps))
     (add-to-list 'compilation-error-regexp-alist 'cargo)
     (add-hook 'next-error-hook #'rustc-scroll-down-after-next-error)))

;;; _
(provide 'rust-compile)
;;; rust-compile.el ends here