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diff --git a/lisp/emacs-lisp/smie.el b/lisp/emacs-lisp/smie.el new file mode 100644 index 00000000000..fb1e4737d39 --- /dev/null +++ b/lisp/emacs-lisp/smie.el @@ -0,0 +1,877 @@ +;;; smie.el --- Simple Minded Indentation Engine + +;; Copyright (C) 2010 Free Software Foundation, Inc. + +;; Author: Stefan Monnier <monnier@iro.umontreal.ca> +;; Keywords: languages, lisp, internal, parsing, indentation + +;; This file is part of GNU Emacs. + +;; GNU Emacs is free software; you can redistribute it and/or modify +;; it under the terms of the GNU General Public License as published by +;; the Free Software Foundation, either version 3 of the License, or +;; (at your option) any later version. + +;; GNU Emacs is distributed in the hope that it will be useful, +;; but WITHOUT ANY WARRANTY; without even the implied warranty of +;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +;; GNU General Public License for more details. + +;; You should have received a copy of the GNU General Public License +;; along with this program. If not, see <http://www.gnu.org/licenses/>. + +;;; Commentary: + +;; While working on the SML indentation code, the idea grew that maybe +;; I could write something generic to do the same thing, and at the +;; end of working on the SML code, I had a pretty good idea of what it +;; could look like. That idea grew stronger after working on +;; LaTeX indentation. +;; +;; So at some point I decided to try it out, by writing a new +;; indentation code for Coq while trying to keep most of the code +;; "table driven", where only the tables are Coq-specific. The result +;; (which was used for Beluga-mode as well) turned out to be based on +;; something pretty close to an operator precedence parser. + +;; So here is another rewrite, this time following the actual principles of +;; operator precedence grammars. Why OPG? Even though they're among the +;; weakest kinds of parsers, these parsers have some very desirable properties +;; for Emacs: +;; - most importantly for indentation, they work equally well in either +;; direction, so you can use them to parse backward from the indentation +;; point to learn the syntactic context; +;; - they work locally, so there's no need to keep a cache of +;; the parser's state; +;; - because of that locality, indentation also works just fine when earlier +;; parts of the buffer are syntactically incorrect since the indentation +;; looks at "as little as possible" of the buffer to make an indentation +;; decision. +;; - they typically have no error handling and can't even detect a parsing +;; error, so we don't have to worry about what to do in case of a syntax +;; error because the parser just automatically does something. Better yet, +;; we can afford to use a sloppy grammar. + +;; The development (especially the parts building the 2D precedence +;; tables and then computing the precedence levels from it) is largely +;; inspired from page 187-194 of "Parsing techniques" by Dick Grune +;; and Ceriel Jacobs (BookBody.pdf available at +;; http://www.cs.vu.nl/~dick/PTAPG.html). +;; +;; OTOH we had to kill many chickens, read many coffee grounds, and practice +;; untold numbers of black magic spells, to come up with the indentation code. +;; Since then, some of that code has been beaten into submission, but the +;; smie-indent-keyword is still pretty obscure. + +;;; Code: + +(eval-when-compile (require 'cl)) + +(defvar comment-continue) +(declare-function comment-string-strip "newcomment" (str beforep afterp)) + +;;; Building precedence level tables from BNF specs. + +(defun smie-set-prec2tab (table x y val &optional override) + (assert (and x y)) + (let* ((key (cons x y)) + (old (gethash key table))) + (if (and old (not (eq old val))) + (if (and override (gethash key override)) + ;; FIXME: The override is meant to resolve ambiguities, + ;; but it also hides real conflicts. It would be great to + ;; be able to distinguish the two cases so that overrides + ;; don't hide real conflicts. + (puthash key (gethash key override) table) + (display-warning 'smie (format "Conflict: %s %s/%s %s" x old val y))) + (puthash key val table)))) + +(defun smie-precs-precedence-table (precs) + "Compute a 2D precedence table from a list of precedences. +PRECS should be a list, sorted by precedence (e.g. \"+\" will +come before \"*\"), of elements of the form \(left OP ...) +or (right OP ...) or (nonassoc OP ...) or (assoc OP ...). All operators in +one of those elements share the same precedence level and associativity." + (let ((prec2-table (make-hash-table :test 'equal))) + (dolist (prec precs) + (dolist (op (cdr prec)) + (let ((selfrule (cdr (assq (car prec) + '((left . >) (right . <) (assoc . =)))))) + (when selfrule + (dolist (other-op (cdr prec)) + (smie-set-prec2tab prec2-table op other-op selfrule)))) + (let ((op1 '<) (op2 '>)) + (dolist (other-prec precs) + (if (eq prec other-prec) + (setq op1 '> op2 '<) + (dolist (other-op (cdr other-prec)) + (smie-set-prec2tab prec2-table op other-op op2) + (smie-set-prec2tab prec2-table other-op op op1))))))) + prec2-table)) + +(defun smie-merge-prec2s (&rest tables) + (if (null (cdr tables)) + (car tables) + (let ((prec2 (make-hash-table :test 'equal))) + (dolist (table tables) + (maphash (lambda (k v) + (smie-set-prec2tab prec2 (car k) (cdr k) v)) + table)) + prec2))) + +(defun smie-bnf-precedence-table (bnf &rest precs) + (let ((nts (mapcar 'car bnf)) ;Non-terminals + (first-ops-table ()) + (last-ops-table ()) + (first-nts-table ()) + (last-nts-table ()) + (prec2 (make-hash-table :test 'equal)) + (override (apply 'smie-merge-prec2s + (mapcar 'smie-precs-precedence-table precs))) + again) + (dolist (rules bnf) + (let ((nt (car rules)) + (last-ops ()) + (first-ops ()) + (last-nts ()) + (first-nts ())) + (dolist (rhs (cdr rules)) + (assert (consp rhs)) + (if (not (member (car rhs) nts)) + (pushnew (car rhs) first-ops) + (pushnew (car rhs) first-nts) + (when (consp (cdr rhs)) + ;; If the first is not an OP we add the second (which + ;; should be an OP if BNF is an "operator grammar"). + ;; Strictly speaking, this should only be done if the + ;; first is a non-terminal which can expand to a phrase + ;; without any OP in it, but checking doesn't seem worth + ;; the trouble, and it lets the writer of the BNF + ;; be a bit more sloppy by skipping uninteresting base + ;; cases which are terminals but not OPs. + (assert (not (member (cadr rhs) nts))) + (pushnew (cadr rhs) first-ops))) + (let ((shr (reverse rhs))) + (if (not (member (car shr) nts)) + (pushnew (car shr) last-ops) + (pushnew (car shr) last-nts) + (when (consp (cdr shr)) + (assert (not (member (cadr shr) nts))) + (pushnew (cadr shr) last-ops))))) + (push (cons nt first-ops) first-ops-table) + (push (cons nt last-ops) last-ops-table) + (push (cons nt first-nts) first-nts-table) + (push (cons nt last-nts) last-nts-table))) + ;; Compute all first-ops by propagating the initial ones we have + ;; now, according to first-nts. + (setq again t) + (while (prog1 again (setq again nil)) + (dolist (first-nts first-nts-table) + (let* ((nt (pop first-nts)) + (first-ops (assoc nt first-ops-table))) + (dolist (first-nt first-nts) + (dolist (op (cdr (assoc first-nt first-ops-table))) + (unless (member op first-ops) + (setq again t) + (push op (cdr first-ops)))))))) + ;; Same thing for last-ops. + (setq again t) + (while (prog1 again (setq again nil)) + (dolist (last-nts last-nts-table) + (let* ((nt (pop last-nts)) + (last-ops (assoc nt last-ops-table))) + (dolist (last-nt last-nts) + (dolist (op (cdr (assoc last-nt last-ops-table))) + (unless (member op last-ops) + (setq again t) + (push op (cdr last-ops)))))))) + ;; Now generate the 2D precedence table. + (dolist (rules bnf) + (dolist (rhs (cdr rules)) + (while (cdr rhs) + (cond + ((member (car rhs) nts) + (dolist (last (cdr (assoc (car rhs) last-ops-table))) + (smie-set-prec2tab prec2 last (cadr rhs) '> override))) + ((member (cadr rhs) nts) + (dolist (first (cdr (assoc (cadr rhs) first-ops-table))) + (smie-set-prec2tab prec2 (car rhs) first '< override)) + (if (and (cddr rhs) (not (member (car (cddr rhs)) nts))) + (smie-set-prec2tab prec2 (car rhs) (car (cddr rhs)) + '= override))) + (t (smie-set-prec2tab prec2 (car rhs) (cadr rhs) '= override))) + (setq rhs (cdr rhs))))) + prec2)) + +(defun smie-prec2-levels (prec2) + "Take a 2D precedence table and turn it into an alist of precedence levels. +PREC2 is a table as returned by `smie-precs-precedence-table' or +`smie-bnf-precedence-table'." + ;; For each operator, we create two "variables" (corresponding to + ;; the left and right precedence level), which are represented by + ;; cons cells. Those are the vary cons cells that appear in the + ;; final `table'. The value of each "variable" is kept in the `car'. + (let ((table ()) + (csts ()) + (eqs ()) + tmp x y) + ;; From `prec2' we construct a list of constraints between + ;; variables (aka "precedence levels"). These can be either + ;; equality constraints (in `eqs') or `<' constraints (in `csts'). + (maphash (lambda (k v) + (if (setq tmp (assoc (car k) table)) + (setq x (cddr tmp)) + (setq x (cons nil nil)) + (push (cons (car k) (cons nil x)) table)) + (if (setq tmp (assoc (cdr k) table)) + (setq y (cdr tmp)) + (setq y (cons nil (cons nil nil))) + (push (cons (cdr k) y) table)) + (ecase v + (= (push (cons x y) eqs)) + (< (push (cons x y) csts)) + (> (push (cons y x) csts)))) + prec2) + ;; First process the equality constraints. + (let ((eqs eqs)) + (while eqs + (let ((from (caar eqs)) + (to (cdar eqs))) + (setq eqs (cdr eqs)) + (if (eq to from) + nil ;Nothing to do. + (dolist (other-eq eqs) + (if (eq from (cdr other-eq)) (setcdr other-eq to)) + (when (eq from (car other-eq)) + ;; This can happen because of `assoc' settings in precs + ;; or because of a rhs like ("op" foo "op"). + (setcar other-eq to))) + (dolist (cst csts) + (if (eq from (cdr cst)) (setcdr cst to)) + (if (eq from (car cst)) (setcar cst to))))))) + ;; Then eliminate trivial constraints iteratively. + (let ((i 0)) + (while csts + (let ((rhvs (mapcar 'cdr csts)) + (progress nil)) + (dolist (cst csts) + (unless (memq (car cst) rhvs) + (setq progress t) + ;; We could give each var in a given iteration the same value, + ;; but we can also give them arbitrarily different values. + ;; Basically, these are vars between which there is no + ;; constraint (neither equality nor inequality), so + ;; anything will do. + ;; We give them arbitrary values, which means that we + ;; replace the "no constraint" case with either > or < + ;; but not =. The reason we do that is so as to try and + ;; distinguish associative operators (which will have + ;; left = right). + (unless (caar cst) + (setcar (car cst) i) + (incf i)) + (setq csts (delq cst csts)))) + (unless progress + (error "Can't resolve the precedence table to precedence levels"))) + (incf i 10)) + ;; Propagate equalities back to their source. + (dolist (eq (nreverse eqs)) + (assert (or (null (caar eq)) (eq (car eq) (cdr eq)))) + (setcar (car eq) (cadr eq))) + ;; Finally, fill in the remaining vars (which only appeared on the + ;; right side of the < constraints). + (dolist (x table) + ;; When both sides are nil, it means this operator binds very + ;; very tight, but it's still just an operator, so we give it + ;; the highest precedence. + ;; OTOH if only one side is nil, it usually means it's like an + ;; open-paren, which is very important for indentation purposes, + ;; so we keep it nil, to make it easier to recognize. + (unless (or (nth 1 x) (nth 2 x)) + (setf (nth 1 x) i) + (setf (nth 2 x) i)))) + table)) + +;;; Parsing using a precedence level table. + +(defvar smie-op-levels 'unset + "List of token parsing info. +Each element is of the form (TOKEN LEFT-LEVEL RIGHT-LEVEL). +Parsing is done using an operator precedence parser. +LEFT-LEVEL and RIGHT-LEVEL can be either numbers or nil, where nil +means that this operator does not bind on the corresponding side, +i.e. a LEFT-LEVEL of nil means this is a token that behaves somewhat like +an open-paren, whereas a RIGHT-LEVEL of nil would correspond to something +like a close-paren.") + +(defvar smie-forward-token-function 'smie-default-forward-token + "Function to scan forward for the next token. +Called with no argument should return a token and move to its end. +If no token is found, return nil or the empty string. +It can return nil when bumping into a parenthesis, which lets SMIE +use syntax-tables to handle them in efficient C code.") + +(defvar smie-backward-token-function 'smie-default-backward-token + "Function to scan backward the previous token. +Same calling convention as `smie-forward-token-function' except +it should move backward to the beginning of the previous token.") + +(defalias 'smie-op-left 'car) +(defalias 'smie-op-right 'cadr) + +(defun smie-default-backward-token () + (forward-comment (- (point))) + (buffer-substring (point) + (progn (if (zerop (skip-syntax-backward ".")) + (skip-syntax-backward "w_'")) + (point)))) + +(defun smie-default-forward-token () + (forward-comment (point-max)) + (buffer-substring (point) + (progn (if (zerop (skip-syntax-forward ".")) + (skip-syntax-forward "w_'")) + (point)))) + +(defun smie-associative-p (toklevels) + ;; in "a + b + c" we want to stop at each +, but in + ;; "if a then b else c" we don't want to stop at each keyword. + ;; To distinguish the two cases, we made smie-prec2-levels choose + ;; different levels for each part of "if a then b else c", so that + ;; by checking if the left-level is equal to the right level, we can + ;; figure out that it's an associative operator. + ;; This is not 100% foolproof, tho, since a grammar like + ;; (exp ("A" exp "C") ("A" exp "B" exp "C")) + ;; will cause "B" to have equal left and right levels, even though + ;; it is not an associative operator. + ;; A better check would be the check the actual previous operator + ;; against this one to see if it's the same, but we'd have to change + ;; `levels' to keep a stack of operators rather than only levels. + (eq (smie-op-left toklevels) (smie-op-right toklevels))) + +(defun smie-next-sexp (next-token next-sexp op-forw op-back halfsexp) + "Skip over one sexp. +NEXT-TOKEN is a function of no argument that moves forward by one +token (after skipping comments if needed) and returns it. +NEXT-SEXP is a lower-level function to skip one sexp. +OP-FORW is the accessor to the forward level of the level data. +OP-BACK is the accessor to the backward level of the level data. +HALFSEXP if non-nil, means skip over a partial sexp if needed. I.e. if the +first token we see is an operator, skip over its left-hand-side argument. +Possible return values: + (FORW-LEVEL POS TOKEN): we couldn't skip TOKEN because its back-level + is too high. FORW-LEVEL is the forw-level of TOKEN, + POS is its start position in the buffer. + (t POS TOKEN): same thing when we bump on the wrong side of a paren. + (nil POS TOKEN): we skipped over a paren-like pair. + nil: we skipped over an identifier, matched parentheses, ..." + (catch 'return + (let ((levels ())) + (while + (let* ((pos (point)) + (token (funcall next-token)) + (toklevels (cdr (assoc token smie-op-levels)))) + + (cond + ((null toklevels) + (when (zerop (length token)) + (condition-case err + (progn (goto-char pos) (funcall next-sexp 1) nil) + (scan-error (throw 'return (list t (caddr err))))) + (if (eq pos (point)) + ;; We did not move, so let's abort the loop. + (throw 'return (list t (point)))))) + ((null (funcall op-back toklevels)) + ;; A token like a paren-close. + (assert (funcall op-forw toklevels)) ;Otherwise, why mention it? + (push (funcall op-forw toklevels) levels)) + (t + (while (and levels (< (funcall op-back toklevels) (car levels))) + (setq levels (cdr levels))) + (cond + ((null levels) + (if (and halfsexp (funcall op-forw toklevels)) + (push (funcall op-forw toklevels) levels) + (throw 'return + (prog1 (list (or (car toklevels) t) (point) token) + (goto-char pos))))) + (t + (if (and levels (= (funcall op-back toklevels) (car levels))) + (setq levels (cdr levels))) + (cond + ((null levels) + (cond + ((null (funcall op-forw toklevels)) + (throw 'return (list nil (point) token))) + ((smie-associative-p toklevels) + (throw 'return + (prog1 (list (or (car toklevels) t) (point) token) + (goto-char pos)))) + ;; We just found a match to the previously pending operator + ;; but this new operator is still part of a larger RHS. + ;; E.g. we're now looking at the "then" in + ;; "if a then b else c". So we have to keep parsing the + ;; rest of the construct. + (t (push (funcall op-forw toklevels) levels)))) + (t + (if (funcall op-forw toklevels) + (push (funcall op-forw toklevels) levels)))))))) + levels) + (setq halfsexp nil))))) + +(defun smie-backward-sexp (&optional halfsexp) + "Skip over one sexp. +HALFSEXP if non-nil, means skip over a partial sexp if needed. I.e. if the +first token we see is an operator, skip over its left-hand-side argument. +Possible return values: + (LEFT-LEVEL POS TOKEN): we couldn't skip TOKEN because its right-level + is too high. LEFT-LEVEL is the left-level of TOKEN, + POS is its start position in the buffer. + (t POS TOKEN): same thing but for an open-paren or the beginning of buffer. + (nil POS TOKEN): we skipped over a paren-like pair. + nil: we skipped over an identifier, matched parentheses, ..." + (smie-next-sexp + (indirect-function smie-backward-token-function) + (indirect-function 'backward-sexp) + (indirect-function 'smie-op-left) + (indirect-function 'smie-op-right) + halfsexp)) + +(defun smie-forward-sexp (&optional halfsexp) + "Skip over one sexp. +HALFSEXP if non-nil, means skip over a partial sexp if needed. I.e. if the +first token we see is an operator, skip over its left-hand-side argument. +Possible return values: + (RIGHT-LEVEL POS TOKEN): we couldn't skip TOKEN because its left-level + is too high. RIGHT-LEVEL is the right-level of TOKEN, + POS is its end position in the buffer. + (t POS TOKEN): same thing but for an open-paren or the beginning of buffer. + (nil POS TOKEN): we skipped over a paren-like pair. + nil: we skipped over an identifier, matched parentheses, ..." + (smie-next-sexp + (indirect-function smie-forward-token-function) + (indirect-function 'forward-sexp) + (indirect-function 'smie-op-right) + (indirect-function 'smie-op-left) + halfsexp)) + +(defun smie-backward-sexp-command (&optional n) + "Move backward through N logical elements." + (interactive "p") + (if (< n 0) + (smie-forward-sexp-command (- n)) + (let ((forward-sexp-function nil)) + (while (> n 0) + (decf n) + (let ((pos (point)) + (res (smie-backward-sexp 'halfsexp))) + (if (and (car res) (= pos (point)) (not (bolp))) + (signal 'scan-error + (list "Containing expression ends prematurely" + (cadr res) (cadr res))) + nil)))))) + +(defun smie-forward-sexp-command (&optional n) + "Move forward through N logical elements." + (interactive "p") + (if (< n 0) + (smie-backward-sexp-command (- n)) + (let ((forward-sexp-function nil)) + (while (> n 0) + (decf n) + (let ((pos (point)) + (res (smie-forward-sexp 'halfsexp))) + (if (and (car res) (= pos (point)) (not (bolp))) + (signal 'scan-error + (list "Containing expression ends prematurely" + (cadr res) (cadr res))) + nil)))))) + +;;; The indentation engine. + +(defcustom smie-indent-basic 4 + "Basic amount of indentation." + :type 'integer) + +(defvar smie-indent-rules 'unset + ;; TODO: For SML, we need more rule formats, so as to handle + ;; structure Foo = + ;; Bar (toto) + ;; and + ;; structure Foo = + ;; struct ... end + ;; I.e. the indentation after "=" depends on the parent ("structure") + ;; as well as on the following token ("struct"). + "Rules of the following form. +\((:before . TOK) . OFFSET-RULES) how to indent TOK itself. +\(TOK . OFFSET-RULES) how to indent right after TOK. +\((T1 . T2) . OFFSET) how to indent token T2 w.r.t T1. +\((t . TOK) . OFFSET) how to indent TOK with respect to its parent. +\(list-intro . TOKENS) declare TOKENS as being followed by what may look like + a funcall but is just a sequence of expressions. +\(t . OFFSET) basic indentation step. +\(args . OFFSET) indentation of arguments. + +OFFSET-RULES is a list of elements which can each either be: + +\(:hanging . OFFSET-RULES) if TOK is hanging, use OFFSET-RULES. +\(:parent PARENT . OFFSET-RULES) if TOK's parent is PARENT, use OFFSET-RULES. +\(:next TOKEN . OFFSET-RULES) if TOK is followed by TOKEN, use OFFSET-RULES. +\(:prev TOKEN . OFFSET-RULES) if TOK is preceded by TOKEN, use OFFSET-RULES. +a number the offset to use. +`point' align with the token. +`parent' align with the parent. + +A nil offset for indentation after a token defaults to `smie-indent-basic'.") + +(defun smie-indent-hanging-p () + ;; A hanging keyword is one that's at the end of a line except it's not at + ;; the beginning of a line. + (and (save-excursion + (when (zerop (length (funcall smie-forward-token-function))) + ;; Could be an open-paren. + (forward-char 1)) + (skip-chars-forward " \t") + (eolp)) + (not (smie-bolp)))) + +(defun smie-bolp () + (save-excursion (skip-chars-backward " \t") (bolp))) + +(defun smie-indent-offset (elem) + (or (cdr (assq elem smie-indent-rules)) + (cdr (assq t smie-indent-rules)) + smie-indent-basic)) + +(defun smie-indent-offset-rule (tokinfo &optional after) + "Apply the OFFSET-RULES in TOKINFO. +Point is expected to be right in front of the token corresponding to TOKINFO. +If computing the indentation after the token, then AFTER is the position +after the token." + (let ((rules (cdr tokinfo)) + parent next prev + offset) + (while (consp rules) + (let ((rule (pop rules))) + (cond + ((not (consp rule)) (setq offset rule)) + ((eq (car rule) :hanging) + (when (smie-indent-hanging-p) + (setq rules (cdr rule)))) + ((eq (car rule) :prev) + (unless prev + (save-excursion + (setq prev (smie-indent-backward-token)))) + (when (equal (car prev) (cadr rule)) + (setq rules (cddr rule)))) + ((eq (car rule) :next) + (unless next + (unless after + (error "Can't use :next in :before indentation rules")) + (save-excursion + (goto-char after) + (setq next (smie-indent-forward-token)))) + (when (equal (car next) (cadr rule)) + (setq rules (cddr rule)))) + ((eq (car rule) :parent) + (unless parent + (save-excursion + (if after (goto-char after)) + (setq parent (smie-backward-sexp 'halfsexp)))) + (when (equal (nth 2 parent) (cadr rule)) + (setq rules (cddr rule)))) + (t (error "Unknown rule %s for indentation of %s" + rule (car tokinfo)))))) + offset)) + +(defun smie-indent-forward-token () + "Skip token forward and return it, along with its levels." + (let ((tok (funcall smie-forward-token-function))) + (cond + ((< 0 (length tok)) (assoc tok smie-op-levels)) + ((looking-at "\\s(") + (forward-char 1) + (list (buffer-substring (1- (point)) (point)) nil 0))))) + +(defun smie-indent-backward-token () + "Skip token backward and return it, along with its levels." + (let ((tok (funcall smie-backward-token-function))) + (cond + ((< 0 (length tok)) (assoc tok smie-op-levels)) + ;; 4 == Open paren syntax. + ((eq 4 (syntax-class (syntax-after (1- (point))))) + (forward-char -1) + (list (buffer-substring (point) (1+ (point))) nil 0))))) + +(defun smie-indent-virtual () + ;; We used to take an optional arg (with value :not-hanging) to specify that + ;; we should only use (smie-indent-calculate) if we're looking at a hanging + ;; keyword. This was a bad idea, because the virtual indent of a position + ;; should not depend on the caller, since it leads to situations where two + ;; dependent indentations get indented differently. + "Compute the virtual indentation to use for point. +This is used when we're not trying to indent point but just +need to compute the column at which point should be indented +in order to figure out the indentation of some other (further down) point." + ;; Trust pre-existing indentation on other lines. + (if (smie-bolp) (current-column) (smie-indent-calculate))) + +(defun smie-indent-fixindent () + ;; Obey the `fixindent' special comment. + (and (smie-bolp) + (save-excursion + (comment-normalize-vars) + (re-search-forward (concat comment-start-skip + "fixindent" + comment-end-skip) + ;; 1+ to account for the \n comment termination. + (1+ (line-end-position)) t)) + (current-column))) + +(defun smie-indent-bob () + ;; Start the file at column 0. + (save-excursion + (forward-comment (- (point))) + (if (bobp) 0))) + +(defun smie-indent-close () + ;; Align close paren with opening paren. + (save-excursion + ;; (forward-comment (point-max)) + (when (looking-at "\\s)") + (while (not (zerop (skip-syntax-forward ")"))) + (skip-chars-forward " \t")) + (condition-case nil + (progn + (backward-sexp 1) + (smie-indent-virtual)) ;:not-hanging + (scan-error nil))))) + +(defun smie-indent-keyword () + ;; Align closing token with the corresponding opening one. + ;; (e.g. "of" with "case", or "in" with "let"). + (save-excursion + (let* ((pos (point)) + (toklevels (smie-indent-forward-token)) + (token (pop toklevels))) + (if (null (car toklevels)) + ;; Different case: + ;; - smie-bolp: "indent according to others". + ;; - common hanging: "indent according to others". + ;; - SML-let hanging: "indent like parent". + ;; - if-after-else: "indent-like parent". + ;; - middle-of-line: "trust current position". + (cond + ((null (cdr toklevels)) nil) ;Not a keyword. + ((smie-bolp) + ;; For an open-paren-like thingy at BOL, always indent only + ;; based on other rules (typically smie-indent-after-keyword). + nil) + (t + (let* ((tokinfo (or (assoc (cons :before token) smie-indent-rules) + ;; By default use point unless we're hanging. + (cons (cons :before token) + '((:hanging nil) point)))) + (after (prog1 (point) (goto-char pos))) + (offset (smie-indent-offset-rule tokinfo))) + (cond + ((eq offset 'point) (current-column)) + ((eq offset 'parent) + (let ((parent (smie-backward-sexp 'halfsexp))) + (if parent (goto-char (cadr parent)))) + (smie-indent-virtual)) + ((eq offset nil) nil) + (t (error "Unhandled offset %s in %s" + offset (cons :before token))))))) + + ;; FIXME: This still looks too much like black magic!! + ;; FIXME: Rather than a bunch of rules like (PARENT . TOKEN), we + ;; want a single rule for TOKEN with different cases for each PARENT. + (let ((res (smie-backward-sexp 'halfsexp)) tmp) + (cond + ((not (or (< (point) pos) + (and (cadr res) (< (cadr res) pos)))) + ;; If we didn't move at all, that means we didn't really skip + ;; what we wanted. + nil) + ((eq (car res) (car toklevels)) + ;; We bumped into a same-level operator. align with it. + (goto-char (cadr res)) + ;; Don't use (smie-indent-virtual :not-hanging) here, because we + ;; want to jump back over a sequence of same-level ops such as + ;; a -> b -> c + ;; -> d + ;; So as to align with the earliest appropriate place. + (smie-indent-virtual)) + ((setq tmp (assoc (cons (caddr res) token) + smie-indent-rules)) + (goto-char (cadr res)) + (+ (cdr tmp) (smie-indent-virtual))) ;:not-hanging + ;; FIXME: The rules ((t . TOK) . OFFSET) either indent + ;; relative to "before the parent" or "after the parent", + ;; depending on details of the grammar. + ((null (car res)) + (assert (eq (point) (cadr res))) + (goto-char (cadr res)) + (+ (or (cdr (assoc (cons t token) smie-indent-rules)) 0) + (smie-indent-virtual))) ;:not-hanging + ((and (= (point) pos) (smie-bolp)) + ;; Since we started at BOL, we're not computing a virtual + ;; indentation, and we're still at the starting point, so the + ;; next (default) rule can't be used since it uses `current-column' + ;; which would cause. indentation to depend on itself. + ;; We could just return nil, but OTOH that's not good enough in + ;; some cases. Instead, we want to combine the offset-rules for + ;; the current token with the offset-rules of the previous one. + (+ (or (cdr (assoc (cons t token) smie-indent-rules)) 0) + ;; FIXME: This is odd. Can't we make it use + ;; smie-indent-(calculate|virtual) somehow? + (smie-indent-after-keyword))) + (t + (+ (or (cdr (assoc (cons t token) smie-indent-rules)) 0) + (current-column))))))))) + +(defun smie-indent-comment () + ;; Indentation of a comment. + (and (looking-at comment-start-skip) + (save-excursion + (forward-comment (point-max)) + (skip-chars-forward " \t\r\n") + (smie-indent-calculate)))) + +(defun smie-indent-comment-continue () + ;; indentation of comment-continue lines. + (let ((continue (and comment-continue + (comment-string-strip comment-continue t t)))) + (and (< 0 (length continue)) + (looking-at (regexp-quote continue)) (nth 4 (syntax-ppss)) + (let ((ppss (syntax-ppss))) + (save-excursion + (forward-line -1) + (if (<= (point) (nth 8 ppss)) + (progn (goto-char (1+ (nth 8 ppss))) (current-column)) + (skip-chars-forward " \t") + (if (looking-at (regexp-quote continue)) + (current-column)))))))) + +(defun smie-indent-after-keyword () + ;; Indentation right after a special keyword. + (save-excursion + (let* ((pos (point)) + (toklevel (smie-indent-backward-token)) + (tok (car toklevel)) + (tokinfo (assoc tok smie-indent-rules))) + (if (and toklevel (null (cadr toklevel)) (null tokinfo)) + (setq tokinfo (list (car toklevel)))) + ;; (if (and tokinfo (null toklevel)) + ;; (error "Token %S has indent rule but has no parsing info" tok)) + (when toklevel + (let ((offset + (cond + (tokinfo (or (smie-indent-offset-rule tokinfo pos) + (smie-indent-offset t))) + ;; The default indentation after a keyword/operator + ;; is 0 for infix and t for prefix. + ;; Using the BNF syntax, we could come up with + ;; better defaults, but we only have the + ;; precedence levels here. + ((null (cadr toklevel)) (smie-indent-offset t)) + (t 0)))) + ;; For indentation after "(let" in SML-mode, we end up accumulating + ;; the offset of "(" and the offset of "let", so we use `min' to try + ;; and get it right either way. + (+ (min (smie-indent-virtual) (current-column)) offset)))))) + +(defun smie-indent-exps () + ;; Indentation of sequences of simple expressions without + ;; intervening keywords or operators. E.g. "a b c" or "g (balbla) f". + ;; Can be a list of expressions or a function call. + ;; If it's a function call, the first element is special (it's the + ;; function). We distinguish function calls from mere lists of + ;; expressions based on whether the preceding token is listed in + ;; the `list-intro' entry of smie-indent-rules. + ;; + ;; TODO: to indent Lisp code, we should add a way to specify + ;; particular indentation for particular args depending on the + ;; function (which would require always skipping back until the + ;; function). + ;; TODO: to indent C code, such as "if (...) {...}" we might need + ;; to add similar indentation hooks for particular positions, but + ;; based on the preceding token rather than based on the first exp. + (save-excursion + (let ((positions nil) + arg) + (while (and (null (car (smie-backward-sexp))) + (push (point) positions) + (not (smie-bolp)))) + (save-excursion + ;; Figure out if the atom we just skipped is an argument rather + ;; than a function. + (setq arg (or (null (car (smie-backward-sexp))) + (member (funcall smie-backward-token-function) + (cdr (assoc 'list-intro smie-indent-rules)))))) + (cond + ((null positions) + ;; We're the first expression of the list. In that case, the + ;; indentation should be (have been) determined by its context. + nil) + (arg + ;; There's a previous element, and it's not special (it's not + ;; the function), so let's just align with that one. + (goto-char (car positions)) + (current-column)) + ((cdr positions) + ;; We skipped some args plus the function and bumped into something. + ;; Align with the first arg. + (goto-char (cadr positions)) + (current-column)) + (positions + ;; We're the first arg. + (goto-char (car positions)) + (+ (smie-indent-offset 'args) + ;; We used to use (smie-indent-virtual), but that + ;; doesn't seem right since it might then indent args less than + ;; the function itself. + (current-column))))))) + +(defvar smie-indent-functions + '(smie-indent-fixindent smie-indent-bob smie-indent-close smie-indent-comment + smie-indent-comment-continue smie-indent-keyword smie-indent-after-keyword + smie-indent-exps) + "Functions to compute the indentation. +Each function is called with no argument, shouldn't move point, and should +return either nil if it has no opinion, or an integer representing the column +to which that point should be aligned, if we were to reindent it.") + +(defun smie-indent-calculate () + "Compute the indentation to use for point." + (run-hook-with-args-until-success 'smie-indent-functions)) + +(defun smie-indent-line () + "Indent current line using the SMIE indentation engine." + (interactive) + (let* ((savep (point)) + (indent (condition-case nil + (save-excursion + (forward-line 0) + (skip-chars-forward " \t") + (if (>= (point) savep) (setq savep nil)) + (or (smie-indent-calculate) 0)) + (error 0)))) + (if (not (numberp indent)) + ;; If something funny is used (e.g. `noindent'), return it. + indent + (if (< indent 0) (setq indent 0)) ;Just in case. + (if savep + (save-excursion (indent-line-to indent)) + (indent-line-to indent))))) + +;;;###autoload +(defun smie-setup (op-levels indent-rules) + (set (make-local-variable 'smie-indent-rules) indent-rules) + (set (make-local-variable 'smie-op-levels) op-levels) + (set (make-local-variable 'indent-line-function) 'smie-indent-line)) + + +(provide 'smie) +;;; smie.el ends here |