When indenting code, limit how far back we search.

Fixes JuliaLang#9254 -- performance is
just too bad on long files otherwise.

contrib/julia-mode.el

@@ -322,6 +322,8 @@ Do not move back beyond position MIN."
 (defun julia-last-open-block (min)
  "Move back and return indentation level for last open block.
 Do not move back beyond MIN."
+ ;; Ensure MIN is not before the start of the buffer.
+ (setq min (max min (point-min)))
  (let ((pos (julia-last-open-block-pos min)))
  (and pos
  (progn
@@ -334,12 +336,26 @@ beginning of the buffer."
  (unless (eq (point) (point-min))
  (backward-char)))
 
+(defvar julia-max-paren-lookback 400
+ "When indenting, don't look back more than this
+many characters to see if there are unclosed parens.
+
+This variable has a major effect on indent performance if set too
+high.")
+
+(defvar julia-max-block-lookback 5000
+ "When indenting, don't look back more than this
+many characters to see if there are unclosed blocks.
+
+This variable has a moderate effect on indent performance if set too
+high.")
+
 (defun julia-paren-indent ()
  "Return the column position of the innermost containing paren
 before point. Returns nil if we're not within nested parens."
  (save-excursion
- (let ((min-pos (or (julia-last-open-block-pos (point-min))
- (point-min)))
+ (let ((min-pos (max (- (point) julia-max-paren-lookback)
+  (point-min)))
  (open-count 0))
  (while (and (> (point) min-pos)
  (not (plusp open-count)))
@@ -383,7 +399,7 @@ before point. Returns nil if we're not within nested parens."
  (beginning-of-line)
  (forward-to-indentation 0)
  (let ((endtok (julia-at-keyword julia-block-end-keywords)))
- (ignore-errors (+ (julia-last-open-block (point-min))
+ (ignore-errors (+ (julia-last-open-block (- (point) julia-max-block-lookback))
  (if endtok (- julia-basic-offset) 0)))))
  ;; Otherwise, use the same indentation as previous line.
  (save-excursion (forward-line -1)