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nix-mode.el
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nix-mode.el
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;;; nix-mode.el --- Major mode for editing .nix files -*- lexical-binding: t -*-
;; Maintainer: Matthew Bauer <mjbauer95@gmail.com>
;; Homepage: https://github.com/NixOS/nix-mode
;; Version: 1.5.0
;; Keywords: nix, languages, tools, unix
;; Package-Requires: ((emacs "25.1") magit-section (transient "0.3"))
;; This file is NOT part of GNU Emacs.
;;; Commentary:
;; A major mode for editing Nix expressions (.nix files). See the Nix manual
;; for more information available at https://nixos.org/nix/manual/.
;;; Code:
(require 'nix)
(require 'nix-format)
(require 'nix-shebang)
(require 'nix-shell)
(require 'nix-repl)
(require 'smie)
(require 'ffap)
(eval-when-compile (require 'subr-x))
(defgroup nix-mode nil
"Nix mode customizations."
:group 'nix)
(defcustom nix-indent-function 'smie-indent-line
"The function to use to indent.
Valid functions for this are:
- ‘indent-relative’
- ‘nix-indent-line' (buggy)
- `smie-indent-line' (‘nix-mode-use-smie’ must be enabled)"
:group 'nix-mode
:type 'function)
(defcustom nix-mode-use-smie t
"Whether to use SMIE when editing Nix files.
This is enabled by default, but can take a while to load with
very large Nix files (all-packages.nix)."
:group 'nix-mode
:type 'boolean)
(defgroup nix-faces nil
"Nix faces."
:group 'nix-mode
:group 'faces)
(defface nix-keyword-face
'((t :inherit font-lock-keyword-face))
"Face used to highlight Nix keywords."
:group 'nix-faces)
(defface nix-keyword-warning-face
'((t :inherit font-lock-warning-face))
"Face used to highlight Nix warning keywords."
:group 'nix-faces)
(defface nix-builtin-face
'((t :inherit font-lock-builtin-face))
"Face used to highlight Nix builtins."
:group 'nix-faces)
(defface nix-constant-face
'((t :inherit font-lock-constant-face))
"Face used to highlight Nix constants."
:group 'nix-faces)
(defface nix-attribute-face
'((t :inherit font-lock-variable-name-face))
"Face used to highlight Nix attributes."
:group 'nix-faces)
(defface nix-antiquote-face
'((t :inherit font-lock-preprocessor-face))
"Face used to highlight Nix antiquotes."
:group 'nix-faces)
(defface nix-store-path-face nil
"Face used to highlight Nix store paths."
:group 'nix-faces)
(defface nix-store-path-realised-face
'((t :inherit 'nix-store-path-face))
"Face used to highlight realised Nix store paths."
:group 'nix-faces)
(defface nix-store-path-unrealised-face
'((t :inherit 'nix-store-path-face))
"Face used to highlight unrealised Nix store paths."
:group 'nix-faces)
;;; Constants
(defconst nix-system-types
'("x86_64-linux" "i686-linux" "aarch64-linux" "x86_64-darwin")
"List of supported systems.")
(defconst nix-keywords
'("if" "then"
"else" "with"
"let" "in"
"rec" "inherit"
"or"))
(defconst nix-builtins
'("builtins" "baseNameOf"
"derivation" "dirOf"
"true" "false" "null"
"isNull" "toString"
"fetchTarball" "import"
"map" "removeAttrs"
"toString" "derivationStrict" "placeholder" "scopedImport" "fromTOML"
"fetchTarball" "fetchGit" "fetchTree" "fetchMercurial"))
(defconst nix-warning-keywords
'("assert" "abort" "throw"))
;;; Regexps
(defconst nix-re-file-path
"[a-zA-Z0-9._\\+-]*\\(/[a-zA-Z0-9._\\+-]+\\)+")
(defconst nix-re-url
"[a-zA-Z][a-zA-Z0-9\\+-\\.]*:[a-zA-Z0-9%/\\?:@&=\\+\\$,_\\.!~\\*'-]+")
(defconst nix-re-bracket-path
"<[a-zA-Z0-9._\\+-]+\\(/[a-zA-Z0-9._\\+-]+\\)*>")
(defconst nix-re-variable-assign
"\\<\\([a-zA-Z_][a-zA-Z0-9_'\-\.]*\\)[ \t]*=[^=]")
(defconst nix-re-caps
" =[ \n]\\|\(\\|\{\\|\\[\\|\\bwith\\b\\|\\blet\\b\\|\\binherit\\b")
(defconst nix-re-ends ";\\|\)\\|\\]\\|\}\\|\\bin\\b")
(defconst nix-re-quotes "''\\|\"")
(defconst nix-re-comments "#\\|/*\\|*/")
(defun nix-re-keywords (keywords)
"Produce a regexp matching some keywords of Nix.
KEYWORDS a list of strings to match as Nix keywords."
(concat
"\\(?:[[:space:];:{}()]\\|^\\)"
(regexp-opt keywords t)
"\\(?:[[:space:];:{}()]\\|$\\)"
))
(defconst nix-font-lock-keywords
`((,(nix-re-keywords nix-keywords) 1 'nix-keyword-face)
(,(nix-re-keywords nix-warning-keywords) 1 'nix-keyword-warning-face)
(,(nix-re-keywords nix-builtins) 1 'nix-builtin-face)
(,nix-re-url 0 'nix-constant-face)
(,nix-re-file-path 0 'nix-constant-face)
(,nix-re-variable-assign 1 'nix-attribute-face)
(,nix-re-bracket-path 0 'nix-constant-face)
(nix--syntax-match-antiquote 0 'nix-antiquote-face t))
"Font lock keywords for nix.")
(defconst nix--variable-char "[a-zA-Z0-9_'\-]")
(defvar nix-mode-abbrev-table
(make-abbrev-table)
"Abbrev table for Nix mode.")
(defvar nix-mode-syntax-table
(let ((table (make-syntax-table)))
(modify-syntax-entry ?/ ". 14" table)
(modify-syntax-entry ?* ". 23" table)
(modify-syntax-entry ?# "< b" table)
(modify-syntax-entry ?\n "> b" table)
(modify-syntax-entry ?_ "_" table)
(modify-syntax-entry ?. "'" table)
(modify-syntax-entry ?- "_" table)
(modify-syntax-entry ?' "'" table)
(modify-syntax-entry ?= "." table)
(modify-syntax-entry ?< "." table)
(modify-syntax-entry ?> "." table)
;; We handle strings
(modify-syntax-entry ?\" "." table)
;; We handle escapes
(modify-syntax-entry ?\\ "." table)
table)
"Syntax table for Nix mode.")
(defun nix--syntax-match-antiquote (limit)
"Find antiquote within a Nix expression up to LIMIT."
(unless (> (point) limit)
(if (get-text-property (point) 'nix-syntax-antiquote)
(progn
(set-match-data (list (point) (1+ (point))))
(forward-char 1)
t)
(let ((pos (next-single-char-property-change (point) 'nix-syntax-antiquote
nil limit)))
(when (and pos (not (> pos limit)))
(goto-char pos)
(let ((char (char-after pos)))
(pcase char
(`?{
(forward-char 1)
(set-match-data (list (1- pos) (point)))
t)
(`?}
(forward-char 1)
(set-match-data (list pos (point)))
t))))))))
(defun nix--mark-string (pos string-type)
"Mark string as a Nix string.
POS position of start of string
STRING-TYPE type of string based off of Emacs syntax table types"
(put-text-property pos (1+ pos)
'syntax-table (string-to-syntax "|"))
(put-text-property pos (1+ pos)
'nix-string-type string-type))
(defun nix--get-parse-state (pos)
"Get the result of `syntax-ppss' at POS."
(save-excursion (save-match-data (syntax-ppss pos))))
(defun nix--get-string-type (parse-state)
"Get the type of string based on PARSE-STATE."
(let ((string-start (nth 8 parse-state)))
(and string-start (get-text-property string-start 'nix-string-type))))
(defun nix--open-brace-string-type (parse-state)
"Determine if this is an open brace string type based on PARSE-STATE."
(let ((open-brace (nth 1 parse-state)))
(and open-brace (get-text-property open-brace 'nix-string-type))))
(defun nix--open-brace-antiquote-p (parse-state)
"Determine if this is an open brace antiquote based on PARSE-STATE."
(let ((open-brace (nth 1 parse-state)))
(and open-brace (get-text-property open-brace 'nix-syntax-antiquote))))
(defun nix--single-quotes ()
"Handle Nix single quotes."
(let* ((start (match-beginning 0))
(end (match-end 0))
(context (nix--get-parse-state start))
(string-type (nix--get-string-type context)))
(unless (or (equal string-type ?\")
(and (equal string-type nil)
(< 1 start)
(string-match-p nix--variable-char
(buffer-substring (1- start) start))))
(when (equal string-type nil)
(nix--mark-string start ?\')
(setq start (+ 2 start)))
(when (equal (mod (- end start) 3) 2)
(let ((str-peek (buffer-substring end (min (point-max) (+ 2 end)))))
(cond
((member str-peek '("${" "\\n" "\\r" "\\t"))
(goto-char (+ 2 end)))
((string-prefix-p "$" str-peek)
(goto-char (1+ end)))
(t
(nix--mark-string (1- end) ?\'))))))))
(defun nix--escaped-dollar-sign-antiquote-sq-style ()
"Hande Nix escaped dollar sign antiquote sq style."
(let* ((start (match-beginning 0))
(ps (nix--get-parse-state start))
(string-type (nix--get-string-type ps)))
(when (equal string-type ?\")
(nix--antiquote-open-at (+ start 2) ?\"))))
(defun nix--escaped-antiquote-dq-style ()
"Handle Nix escaped antiquote dq style."
(let* ((start (match-beginning 0))
(ps (nix--get-parse-state start))
(string-type (nix--get-string-type ps)))
(when (equal string-type ?\')
(nix--antiquote-open-at (1+ start) ?\'))))
(defun nix--double-quotes ()
"Handle Nix double quotes."
(let* ((pos (match-beginning 0))
(ps (nix--get-parse-state pos))
(string-type (nix--get-string-type ps)))
(unless (equal string-type ?\')
(nix--mark-string pos ?\"))))
(defun nix--antiquote-open-at (pos string-type)
"Handle Nix antiquote open at based on POS and STRING-TYPE."
(put-text-property pos (1+ pos)
'syntax-table (string-to-syntax "|"))
(put-text-property pos (+ 2 pos)
'nix-string-type string-type)
(put-text-property (1+ pos) (+ 2 pos)
'nix-syntax-antiquote t))
(defun nix--antiquote-open ()
"Handle Nix antiquote open."
(let* ((start (match-beginning 0))
(ps (nix--get-parse-state start))
(string-type (nix--get-string-type ps)))
(when string-type
(nix--antiquote-open-at start string-type))))
(defun nix--antiquote-close-open ()
"Handle Nix antiquote close then open."
(let* ((start (match-beginning 0))
(ps (nix--get-parse-state start))
(string-type (nix--get-string-type ps)))
(if string-type
(nix--antiquote-open-at (1+ start) string-type)
(when (nix--open-brace-antiquote-p ps)
(let ((string-type (nix--open-brace-string-type ps)))
(put-text-property start (+ 3 start)
'nix-string-type string-type)
(put-text-property start (1+ start)
'nix-syntax-antiquote t)
(put-text-property (+ 2 start) (+ 3 start)
'nix-syntax-antiquote t))))))
(defun nix--antiquote-close ()
"Handle Nix antiquote close."
(let* ((start (match-beginning 0))
(ps (nix--get-parse-state start)))
(unless (nix--get-string-type ps)
(let ((string-type (nix--open-brace-string-type ps)))
(when string-type
(put-text-property start (1+ start)
'nix-string-type string-type)
(put-text-property start (1+ start)
'nix-syntax-antiquote t)
(let ((ahead (buffer-substring (1+ start)
(min (point-max) (+ 5 start)))))
(pcase string-type
(`?\" (cond
((or (string-match "^\\\\\"" ahead)
(string-match "^\\\\\\${" ahead))
(nix--mark-string (1+ start) string-type)
(goto-char (+ start (match-end 0) 1)))
((string-match-p "^\"" ahead)
(goto-char (+ 2 start)))
((< (1+ start) (point-max))
(nix--mark-string (1+ start) string-type)
(goto-char (+ 2 start)))))
(`?\' (cond
((or (string-match "^'''" ahead)
(string-match "^''\\${" ahead)
(string-match "^''\\\\[nrt]" ahead))
(nix--mark-string (1+ start) string-type)
(goto-char (+ start (match-end 0) 1)))
((string-match-p "^''" ahead)
(goto-char (+ 3 start)))
((< (1+ start) (point-max))
(nix--mark-string (1+ start) string-type)
(goto-char (+ 2 start))))))))))))
(defun nix-syntax-propertize (start end)
"Special syntax properties for Nix from START to END."
(goto-char start)
(remove-text-properties start end
'(nix-string-type nil nix-syntax-antiquote nil))
(funcall
(syntax-propertize-rules
("\\\\\\\\"
(0 nil))
("\\\\\""
(0 nil))
("\\$\\$"
(0 nil))
("\\\\\\$\\${"
(0 (ignore (nix--escaped-dollar-sign-antiquote-sq-style))))
("\\\\\\${"
(0 (ignore (nix--escaped-antiquote-dq-style))))
("'\\{2,\\}"
(0 (ignore (nix--single-quotes))))
("}\\${"
(0 (ignore (nix--antiquote-close-open))))
("\\${"
(0 (ignore (nix--antiquote-open))))
("}"
(0 (ignore (nix--antiquote-close))))
("\""
(0 (ignore (nix--double-quotes)))))
start end))
;; Indentation using SMIE
(defconst nix-smie-grammar
(smie-prec2->grammar
(smie-merge-prec2s
(smie-bnf->prec2
'((id)
(expr (arg ":" expr)
("if" expr "then" expr "else" expr)
("let" decls "in" expr)
("with" expr "nonsep-;" expr)
("assert" expr "nonsep-;" expr)
(attrset)
(id))
(attrset ("{" decls "}"))
(decls (decls ";" decls)
(id "=" expr))
(arg (id) ("{" args "}"))
(args (args "," args) (id "arg-?" expr)))
'((assoc ";"))
'((assoc ","))
;; resolve "(with foo; a) <op> b" vs "with foo; (a <op> b)"
;; in favor of the latter.
'((nonassoc "nonsep-;") (nonassoc " -dummy- "))
;; resolve "(if ... then ... else a) <op> b"
;; vs "if ... then ... else (a <op> b)" in favor of the latter.
'((nonassoc "in") (nonassoc " -dummy- ")))
(smie-precs->prec2
'((nonassoc " -dummy- ")
(nonassoc "=")
;; " -bexpskip- " and " -fexpskip- " are handy tokens for skipping over
;; whole expressions.
;; For instance, suppose we have a line looking like this:
;; "{ foo.bar // { x = y }"
;; and point is at the end of the line. We can skip the whole
;; expression (i.e. so the point is just before "foo") using
;; `(smie-backward-sexp " -bexpskip- ")'. `(backward-sexp)' would
;; skip over "{ x = y }", not over the whole expression.
(right " -bexpskip- ")
(left " -fexpskip- ")
(nonassoc "else")
(right ":")
(right "->")
(assoc "||")
(assoc "&&")
(nonassoc "==" "!=")
(nonassoc "<" "<=" ">" ">=")
(left "//")
(nonassoc "!")
(assoc "-" "+")
(assoc "*" "/")
(assoc "++")
(left "?")
;; Tokens for skipping sequences of sexps
;; (i.e. identifiers or balanced parens).
;; For instance, suppose we have a line looking like this:
;; "{ foo.bar // f x "
;; and point is at the end of the line. We can skip the "f x"
;; part by doing `(smie-backward-sexp " -bseqskip- ")'.
(right " -bseqskip- ")
(left " -fseqskip- "))))))
(defconst nix-smie--2char-symbols
'("->" "||" "&&" "==" "!=" "<=" ">=" "++" "//"))
(defconst nix-smie--infix-symbols-re
(regexp-opt (append '(":" "<" ">" "-" "+" "*" "/" "?")
nix-smie--2char-symbols)))
(defconst nix-smie-indent-tokens-re
(regexp-opt '("{" "(" "[" "=" "let" "if" "then" "else")))
;; The core indentation algorithm is very simple:
;; - If the last token on the previous line matches `nix-smie-indent-tokens-re',
;; then the current line is indented by `tab-width' relative to the
;; previous line's 'anchor'.
;; - Otherwise, let SMIE handle it.
;; The 'anchor' of a line is defined as follows:
;; - If the line contains an assignment, it is the beginning of the
;; left-hand side of the first assignment on that line.
;; - Otherwise, it is the position of the first token on that line.
(defun nix-smie-rules (kind token)
"Core smie rules."
(pcase (cons kind token)
(`(:after . ,(guard (string-match-p nix-smie-indent-tokens-re
token)))
(nix-smie--indent-anchor))
(`(,_ . "in")
(let ((bol (line-beginning-position)))
(forward-word)
;; Go back to the corresponding "let".
(smie-backward-sexp t)
(pcase kind
(:before
(if (smie-rule-hanging-p)
(nix-smie--indent-anchor 0)
`(column . ,(current-column))))
(:after
(cond
((bolp) '(column . 0))
((<= bol (point))
`(column . ,(current-column))))))))
(`(:after . "nonsep-;")
(forward-char)
(backward-sexp)
(if (smie-rule-bolp)
`(column . ,(current-column))
(nix-smie--indent-anchor)))
(`(:after . ":")
(or (nix-smie--indent-args-line)
(nix-smie--indent-anchor)))
(`(:after . ",")
(smie-rule-parent tab-width))
(`(:before . ",")
;; The parent is either the enclosing "{" or some previous ",".
;; In both cases this is what we want to align to.
(smie-rule-parent))
(`(:before . "if")
(let ((bol (line-beginning-position)))
(save-excursion
(and
(equal (nix-smie--backward-token) "else")
(<= bol (point))
`(column . ,(current-column))))))
(`(:before . ,(guard (string-match-p nix-smie--infix-symbols-re token)))
(forward-comment (- (point)))
(let ((bol (line-beginning-position)))
(smie-backward-sexp token)
(if (< (point) bol)
(nix-smie--indent-anchor 0))))))
(defun nix-smie--anchor ()
"Return the anchor's offset from the beginning of the current line."
(save-excursion
(beginning-of-line)
(let ((eol (line-end-position))
anchor
tok)
(forward-comment (point-max))
(unless (or (eobp) (< eol (point)))
(setq anchor (current-column))
(catch 'break
(while (and (not (eobp))
(progn
(setq tok (car (smie-indent-forward-token)))
(<= (point) eol)))
(when (equal "=" tok)
(backward-char)
(smie-backward-sexp " -bseqskip- ")
(setq anchor (current-column))
(throw 'break nil))))
anchor))))
(defun nix-smie--indent-anchor (&optional indent)
"Intended for use only in the rules function."
(let ((indent (or indent tab-width)))
`(column . ,(+ indent (nix-smie--anchor)))))
(defun nix-smie--indent-args-line ()
"Indent the body of a lambda whose argument(s) are on a line of their own."
(save-excursion
;; Assume that point is right before ':', skip it
(forward-char)
(let ((tok ":"))
(catch 'break
(while (equal tok ":")
(setq tok (nth 2 (smie-backward-sexp t)))
(when (smie-rule-bolp)
(throw 'break `(column . ,(current-column)))))))))
(defconst nix-smie--path-chars "a-zA-Z0-9-+_.:/~")
(defun nix-smie--skip-angle-path-forward ()
"Skip forward a path enclosed in angle brackets, e.g <nixpkgs>."
(let ((start (point)))
(when (eq (char-after) ?<)
(forward-char)
(if (and (nix-smie--skip-path 'forward t)
(eq (char-after) ?>))
(progn
(forward-char)
(buffer-substring-no-properties start (point)))
(ignore (goto-char start))))))
(defun nix-smie--skip-angle-path-backward ()
"Skip backward a path enclosed in angle brackets, e.g <nixpkgs>."
(let ((start (point)))
(when (eq (char-before) ?>)
(backward-char)
(if (and (nix-smie--skip-path 'backward t)
(eq (char-before) ?<))
(progn
(backward-char)
(buffer-substring-no-properties start (point)))
(ignore (goto-char start))))))
(defun nix-smie--skip-path (how &optional no-sep-check)
"Skip path related characters."
(let ((start (point)))
(pcase-exhaustive how
('forward (skip-chars-forward nix-smie--path-chars))
('backward (skip-chars-backward nix-smie--path-chars)))
(let ((sub (buffer-substring-no-properties start (point))))
(if (or (and no-sep-check
(< 0 (length sub)))
(string-match-p "/" sub))
sub
(ignore (goto-char start))))))
;; Returns non-nil if it successfully skipped a symbol.
(defun nix-smie--skip-symbol (how)
(let* ((start (point))
(nskip (pcase-exhaustive how
('backward (skip-syntax-backward "._"))
('forward (skip-syntax-forward "._"))))
(abs-skip (abs nskip)))
(or (= 1 abs-skip)
(and (= 2 abs-skip)
(member (buffer-substring-no-properties (point) start)
nix-smie--2char-symbols))
(if (< 0 abs-skip)
(goto-char (+ start (if (< 0 nskip) 1 -1)))
(goto-char start)
nil))))
(defun nix-smie--forward-token-1 ()
"Move forward one token."
(forward-comment (point-max))
(or (nix-smie--skip-angle-path-forward)
(nix-smie--skip-path 'forward)
(buffer-substring-no-properties
(point)
(progn
(or (/= 0 (skip-syntax-forward "'w_"))
(nix-smie--skip-symbol 'forward))
(point)))))
(defun nix-smie--forward-token ()
"Move forward one token, skipping certain characters."
(let ((sym (nix-smie--forward-token-1)))
(if (member sym '(";" "?"))
;; The important lexer for indentation's performance is the backward
;; lexer, so for the forward lexer we delegate to the backward one.
(save-excursion (nix-smie--backward-token))
sym)))
(defun nix-smie--backward-token-1 ()
"Move backward one token."
(forward-comment (- (point)))
(or (nix-smie--skip-angle-path-backward)
(nix-smie--skip-path 'backward)
(buffer-substring-no-properties
(point)
(progn
(or (/= 0 (skip-syntax-backward "'w_"))
(nix-smie--skip-symbol 'backward))
(point)))))
(defun nix-smie--backward-token ()
"Move backward one token, skipping certain characters."
(let ((sym (nix-smie--backward-token-1)))
(unless (zerop (length sym))
(pcase sym
(";" (if (nix-smie--nonsep-semicolon-p) "nonsep-;" ";"))
("?" (if (nix-smie--arg-?-p) "arg-?" "?"))
(_ sym)))))
(defun nix-smie--nonsep-semicolon-p ()
"Whether the semicolon at point terminates a `with' or `assert'."
(save-excursion
(member (nth 2 (smie-backward-sexp " -bexpskip- ")) '("with" "assert"))))
(defun nix-smie--arg-?-p ()
"Whether the question mark at point is part of an argument declaration."
(member
(nth 2 (progn
(smie-backward-sexp)
(smie-backward-sexp)))
'("{" ",")))
(defun nix-smie--eol-p ()
"Whether there are no tokens after point on the current line."
(let ((eol (line-end-position)))
(save-excursion
(forward-comment (point-max))
(or (eobp)
(< eol (point))))))
(defun nix-smie--indent-close ()
"Align close paren with opening paren."
(save-excursion
(when (looking-at "\\s)")
(forward-char 1)
(condition-case nil
(progn
(backward-sexp 1)
;; If the opening paren is not the last token on its line,
;; and it's either '[' or '{', align to the opening paren's
;; position. Otherwise, align its line's anchor.
(if (and (memq (char-after) '(?\[ ?{))
(not (save-excursion (forward-char) (nix-smie--eol-p))))
(current-column)
(nix-smie--anchor)))
(scan-error nil)))))
(defun nix-smie--indent-exps ()
"This function replaces and is based on `smie-indent-exps'.
An argument to a function is indented relative to the function,
not to any other arguments."
(save-excursion
(let (parent ;; token enclosing the expression list
skipped) ;; whether we skipped at least one expression
(let ((start (point)))
(setq parent (nth 2 (smie-backward-sexp " -bseqskip- ")))
(setq skipped (not (eq start (point))))
(cond
((not skipped)
;; We're the first expression of the list. In that case, the
;; indentation should be (have been) determined by its context.
nil)
((equal parent "[")
;; It's a list, align with the first expression.
(current-column))
;; We're an argument.
(t
;; We can use (current-column) or (current-indentation) here.
;; (current-column) will indent relative to the first expression
;; in the sequence, and (current-indentation) will indent relative
;; to the indentation of the line on which the first expression
;; begins. I'm not sure which one is better.
(+ tab-width (current-indentation))))))))
;;; Indentation not using SMIE
(defun nix-find-backward-matching-token ()
"Find the previous Nix token."
(cond
((looking-at "in\\b")
(let ((counter 1))
(while (and (> counter 0)
(re-search-backward "\\b\\(let\\|in\\)\\b" nil t))
(unless (or (nix--get-string-type (nix--get-parse-state (point)))
(nix-is-comment-p))
(setq counter (cond ((looking-at "let") (- counter 1))
((looking-at "in") (+ counter 1))))))
counter ))
((looking-at "}")
(backward-up-list) t)
((looking-at "]")
(backward-up-list) t)
((looking-at ")")
(backward-up-list) t)))
(defun nix-indent-to-backward-match ()
"Match the previous line’s indentation."
(let ((matching-indentation (save-excursion
(beginning-of-line)
(skip-chars-forward "[:space:]")
(if (nix-find-backward-matching-token)
(current-indentation)))))
(when matching-indentation (indent-line-to matching-indentation) t)))
(defun nix-indent-first-line-in-block ()
"Indent the first line in a block."
(let ((matching-indentation (save-excursion
;; Go back to previous line that contain anything useful to check the
;; contents of that line.
(beginning-of-line)
(skip-chars-backward "\n[:space:]")
;; Grab the full string of the line before the one we're indenting
(let ((line (buffer-substring-no-properties (line-beginning-position) (line-end-position))))
;; Then regex-match strings at the end of the line to detect if we need to indent the line after.
;; We could probably add more things to look for here in the future.
(if (or (string-match "\\blet$" line)
(string-match "\\bimport$" line)
(string-match "\\[$" line)
(string-match "=$" line)
(string-match "\($" line)
(string-match "\{$" line))
;; If it matches any of the regexes above, grab the indent level
;; of the line and add 2 to ident the line below this one.
(+ 2 (current-indentation)))))))
(when matching-indentation (indent-line-to matching-indentation) t)))
(defun nix-mode-search-backward ()
"Search backward for items of interest regarding indentation."
(re-search-backward nix-re-ends nil t)
(re-search-backward nix-re-quotes nil t)
(re-search-backward nix-re-caps nil t))
(defun nix-indent-expression-start ()
"Indent the start of a nix expression."
(let* ((ends 0)
(once nil)
(done nil)
(indent (current-indentation)))
(save-excursion
;; we want to indent this line, so we don't care what it
;; contains skip to the beginning so reverse searching doesn't
;; find any matches within
(beginning-of-line)
;; search backward until an unbalanced cap is found or no cap or
;; end is found
(while (and (not done) (nix-mode-search-backward))
(cond
((looking-at nix-re-quotes)
;; skip over strings entirely
(re-search-backward nix-re-quotes nil t))
((looking-at nix-re-comments)
;; skip over comments entirely
(re-search-backward nix-re-comments nil t))
((looking-at nix-re-ends)
;; count the matched end
;; this means we expect to find at least one more cap
(setq ends (+ ends 1)))
((looking-at nix-re-caps)
;; we found at least one cap
;; this means our function will return true
;; this signals to the caller we handled the indentation
(setq once t)
(if (> ends 0)
;; this cap corresponds to a previously matched end
;; reduce the number of unbalanced ends
(setq ends (- ends 1))
;; no unbalanced ends correspond to this cap
;; this means we have found the expression that contains our line
;; we want to indent relative to this line
(setq indent (current-indentation))
;; signal that the search loop should exit
(setq done t))))))
;; done is t when we found an unbalanced expression cap
(when done
;; indent relative to the indentation of the expression
;; containing our line
(indent-line-to (+ tab-width indent)))
;; return t to the caller if we found at least one cap
;; this signals that we handled the indentation
once))
(defun nix-indent-prev-level ()
"Get the indent level of the previous line."
(save-excursion
(beginning-of-line)
(skip-chars-backward "\n[:space:]")
(current-indentation)))
;;;###autoload
(defun nix-mode-format ()
"Format the entire `nix-mode' buffer."
(interactive)
(when (eq major-mode 'nix-mode)
(save-excursion
(goto-char (point-min))
(while (not (equal (point) (point-max)))
(if (equal (string-match-p "^[\s-]*$" (thing-at-point 'line)) 0)
(delete-horizontal-space)
(nix-indent-line))
(forward-line)))))
;;;###autoload
(defun nix-indent-line ()
"Indent current line in a Nix expression."
(interactive)
(let ((end-of-indentation
(save-excursion
(cond
;; Indent first line of file to 0
((= (line-number-at-pos) 1)
(indent-line-to 0))
;; comment
((save-excursion
(beginning-of-line)
(nix-is-comment-p))
(indent-line-to (nix-indent-prev-level)))
;; string
((save-excursion
(beginning-of-line)
(nth 3 (syntax-ppss)))
(indent-line-to (+ (nix-indent-prev-level)
(* tab-width
(+ (if (save-excursion
(forward-line -1)
(end-of-line)
(skip-chars-backward "[:space:]")
(looking-back "''" 0)) 1 0)
(if (save-excursion
(beginning-of-line)
(skip-chars-forward
"[:space:]")
(looking-at "''")
) -1 0)
)))))
;; dedent '}', ']', ')' 'in'
((nix-indent-to-backward-match))
;; indent line after 'let', 'import', '[', '=', '(', '{'
((nix-indent-first-line-in-block))
;; indent between = and ; + 2, or to 2
((nix-indent-expression-start))
;; else
(t
(indent-line-to (nix-indent-prev-level))))
(point))))
(when (> end-of-indentation (point)) (goto-char end-of-indentation))))
(defun nix-is-comment-p ()
"Whether we are in a comment."
(nth 4 (syntax-ppss)))
(defun nix-is-string-p ()
"Whether we are in a string."
(or (looking-at nix-re-quotes)
(nix--get-string-type (nix--get-parse-state (point)))))
;;;###autoload
(defun nix-indent-region (start end)
"Indent on a whole region. Enabled by default.
START where to start in region.
END where to end the region."
(interactive (list (region-beginning) (region-end)))
(save-excursion
(goto-char start)
(while (< (point) end)
(or (and (bolp) (eolp))
(when (and
;; Skip if previous line is empty or a comment.
(save-excursion
(let ((line-is-comment-p (nix-is-comment-p)))
(forward-line -1)
(not
(or (and (nix-is-comment-p)
;; Unless this line is a comment too.
(not line-is-comment-p))
(nix-is-comment-p)))))
;; Don't mess with strings.
(nix-is-string-p))
(funcall nix-indent-function)))
(forward-line 1))))
;;;###autoload
(defun nix-mode-ffap-nixpkgs-path (str)
"Support `ffap' for <nixpkgs> declarations.
If STR contains brackets, call `nix-instantiate' to find the
location of STR. If `nix-instantiate' has a nonzero exit code,
don’t do anything"
(when (and (string-match nix-re-bracket-path str)
(executable-find nix-instantiate-executable))
(let ((nix-executable nix-instantiate-executable))
(ignore-errors
(nix--process-string "--eval" "-E" str)))))
;; Key maps
(defvar nix-mode-menu (make-sparse-keymap "Nix")
"Menu for Nix mode.")
(defvar nix-mode-map (make-sparse-keymap)
"Local keymap used for Nix mode.")
(defun nix-create-keymap ()
"Create the keymap associated with the Nix mode."
)
(defun nix-create-menu ()
"Create the Nix menu as shown in the menu bar."
(let ((m '("Nix"
["Format buffer" nix-format-buffer t])))
(easy-menu-define nix-mode-menu nix-mode-map "Menu keymap for Nix mode" m)))
(nix-create-keymap)
(nix-create-menu)
;;;###autoload
(define-derived-mode nix-mode prog-mode "Nix"
"Major mode for editing Nix expressions.
The following commands may be useful:
'\\[newline-and-indent]'
Insert a newline and move the cursor to align with the previous
non-empty line.
'\\[fill-paragraph]'
Refill a paragraph so that all lines are at most `fill-column'
lines long. This should do the right thing for comments beginning
with `#'. However, this command doesn't work properly yet if the
comment is adjacent to code (i.e., no intervening empty lines).
In that case, select the text to be refilled and use
`\\[fill-region]' instead.
The hook `nix-mode-hook' is run when Nix mode is started.
\\{nix-mode-map}"
:group 'nix-mode
:syntax-table nix-mode-syntax-table
:abbrev-table nix-mode-abbrev-table
;; Disable hard tabs and set tab to 2 spaces
;; Recommended by nixpkgs manual: https://nixos.org/nixpkgs/manual/#sec-syntax
(setq-local indent-tabs-mode nil)
(setq-local tab-width 2)
(setq-local electric-indent-chars '(?\n ?{ ?} ?\[ ?\] ?\( ?\)))