diff --git a/lisp/progmodes/js.el b/lisp/progmodes/js.el index e84215d4301..54df3913fc6 100644 --- a/lisp/progmodes/js.el +++ b/lisp/progmodes/js.el @@ -552,6 +552,20 @@ don't indent the first one's initializer; otherwise, indent it. :safe 'symbolp :group 'js) +(defcustom js-chain-indent nil + "Use \"chained\" indentation. +Chained indentation applies when the current line starts with \".\". +If the previous expression also contains a \".\" at the same level, +then the \".\"s will be lined up: + + let x = svg.mumble() + .chained; +" + :version "26.1" + :type 'boolean + :safe 'booleanp + :group 'js) + ;;; KeyMap (defvar js-mode-map @@ -1808,6 +1822,63 @@ This performs fontification according to `js--class-styles'." (and (progn (backward-char) (not (looking-at "+\\+\\|--\\|/[/*]")))))))))) +(defun js--skip-term-backward () + "Skip a term before point; return t if a term was skipped." + (let ((term-skipped nil)) + ;; Skip backward over balanced parens. + (let ((progress t)) + (while progress + (setq progress nil) + ;; First skip whitespace. + (skip-syntax-backward " ") + ;; Now if we're looking at closing paren, skip to the opener. + ;; This doesn't strictly follow JS syntax, in that we might + ;; skip something nonsensical like "()[]{}", but it is enough + ;; if it works ok for valid input. + (when (memq (char-before) '(?\] ?\) ?\})) + (setq progress t term-skipped t) + (backward-list)))) + ;; Maybe skip over a symbol. + (let ((save-point (point))) + (if (and (< (skip-syntax-backward "w_") 0) + (looking-at js--name-re)) + ;; Skipped. + (progn + (setq term-skipped t) + (skip-syntax-backward " ")) + ;; Did not skip, so restore point. + (goto-char save-point))) + (when (and term-skipped (> (point) (point-min))) + (backward-char) + (eq (char-after) ?.)))) + +(defun js--skip-terms-backward () + "Skip any number of terms backward. +Move point to the earliest \".\" without changing paren levels. +Returns t if successful, nil if no term was found." + (when (js--skip-term-backward) + ;; Found at least one. + (let ((last-point (point))) + (while (js--skip-term-backward) + (setq last-point (point))) + (goto-char last-point) + t))) + +(defun js--chained-expression-p () + "A helper for js--proper-indentation that handles chained expressions. +A chained expression is when the current line starts with '.' and the +previous line also has a '.' expression. +This function returns the indentation for the current line if it is +a chained expression line; otherwise nil. +This should only be called while point is at the start of the line's content, +as determined by `back-to-indentation'." + (when js-chain-indent + (save-excursion + (when (and (eq (char-after) ?.) + (js--continued-expression-p) + (js--find-newline-backward) + (js--skip-terms-backward)) + (current-column))))) (defun js--end-of-do-while-loop-p () "Return non-nil if point is on the \"while\" of a do-while statement. @@ -1984,6 +2055,7 @@ indentation is aligned to that column." ;; At or after the first loop? (>= (point) beg) (js--array-comp-indentation bracket beg)))) + ((js--chained-expression-p)) ((js--ctrl-statement-indentation)) ((js--multi-line-declaration-indentation)) ((nth 1 parse-status) diff --git a/test/manual/indent/js-chain.js b/test/manual/indent/js-chain.js new file mode 100644 index 00000000000..2a290294026 --- /dev/null +++ b/test/manual/indent/js-chain.js @@ -0,0 +1,29 @@ +// Normal chaining. +let x = svg.mumble() + .zzz; + +// Chaining with an intervening line comment. +let x = svg.mumble() // line comment + .zzz; + +// Chaining with multiple dots. +let x = svg.selectAll().something() + .zzz; + +// Nested chaining. +let x = svg.selectAll(d3.svg.something() + .zzz); + +// Nothing to chain to. +let x = svg() + .zzz; + +// Nothing to chain to. +let x = svg().mumble.x() + 73 + .zzz; + +// Local Variables: +// indent-tabs-mode: nil +// js-chain-indent: t +// js-indent-level: 2 +// End: diff --git a/test/manual/indent/js.js b/test/manual/indent/js.js index d004b82f8bc..846c3a1a5c2 100644 --- a/test/manual/indent/js.js +++ b/test/manual/indent/js.js @@ -124,6 +124,10 @@ if (x > 72 && do_something(); } +// Test that chaining doesn't happen when js-chain-indent is nil. +let x = svg.mumble() + .zzz; + // Local Variables: // indent-tabs-mode: nil // js-indent-level: 2