Add Emacs editor mode. Contributed by Alexandre Vassalotti.

CONTRIBUTORS.txt

@@ -68,3 +68,5 @@ Patch contributors:
     * Fixed initialization ordering problem in logging code.
   Will Pierce <willp@nuclei.com>
     * Small patch improving performance of in Python serialization.
+  Alexandre Vassalotti <alexandre@peadrop.com>
+    * Emacs mode for Protocol Buffers (editors/protobuf-mode.el).

Makefile.am

@@ -42,6 +42,7 @@ EXTRA_DIST =                                                                 \
   CHANGES.txt                                                                \
   editors/README.txt                                                         \
   editors/proto.vim                                                          \
+  editors/protobuf-mode.el                                                   \
   vsprojects/config.h                                                        \
   vsprojects/extract_includes.bat                                            \
   vsprojects/libprotobuf.vcproj                                              \

editors/protobuf-mode.el

+;;; protobuf-mode.el --- major mode for editing protocol buffers.
+
+;; Author: Alexandre Vassalotti <alexandre@peadrop.com>
+;; Created: 23-Apr-2009
+;; Version: 0.3
+;; Keywords: google protobuf languages
+
+;; Redistribution and use in source and binary forms, with or without
+;; modification, are permitted provided that the following conditions are
+;; met:
+;;
+;;     * Redistributions of source code must retain the above copyright
+;; notice, this list of conditions and the following disclaimer.
+;;     * Redistributions in binary form must reproduce the above
+;; copyright notice, this list of conditions and the following disclaimer
+;; in the documentation and/or other materials provided with the
+;; distribution.
+;;     * Neither the name of Google Inc. nor the names of its
+;; contributors may be used to endorse or promote products derived from
+;; this software without specific prior written permission.
+;;
+;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+;; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+;; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+;; A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+;; OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+;; SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+;; LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+;; DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+;; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+;; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+;; OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+;;; Commentary:
+
+;; Installation:
+;;   - Put `protobuf-mode.el' in your Emacs load-path.
+;;   - Add this line to your .emacs file:
+;;       (require 'protobuf-mode)
+;;
+;; You can customize this mode just like any mode derived from CC Mode.  If
+;; you want to add customizations specific to protobuf-mode, you can use the
+;; `protobuf-mode-hook'. For example, the following would make protocol-mode
+;; use 2-space indentation:
+;;
+;;   (defconst my-protobuf-style
+;;     '((c-basic-offset . 2)
+;;       (indent-tabs-mode . nil)))
+;;
+;;   (add-hook 'protobuf-mode-hook
+;;     (lambda () (c-add-style "my-style" my-protobuf-style t)))
+;;
+;; Refer to the documentation of CC Mode for more information about
+;; customization details and how to use this mode.
+;;
+;; TODO:
+;;   - Make highlighting for enum values work properly.
+;;   - Fix the parser to recognize extensions as identifiers and not
+;;     as casts.
+;;   - Improve the parsing of option assignment lists. For example:
+;;       optional int32 foo = 1 [(my_field_option) = 4.5];
+;;   - Add support for fully-qualified identifiers (e.g., with a leading ".").
+
+;;; Code:
+
+(require 'cc-mode)
+
+(eval-when-compile
+  (require 'cc-langs)
+  (require 'cc-fonts))
+
+;; This mode does not inherit properties from other modes. So, we do not use 
+;; the usual `c-add-language' function.
+(put 'protobuf-mode 'c-mode-prefix "protobuf-")
+
+;; The following code uses of the `c-lang-defconst' macro define syntactic
+;; features of protocol buffer language.  Refer to the documentation in the
+;; cc-langs.el file for information about the meaning of the -kwds variables.
+
+(c-lang-defconst c-primitive-type-kwds
+  protobuf '("double" "float" "int32" "int64" "uint32" "uint64" "sint32"
+             "sint64" "fixed32" "fixed64" "sfixed32" "sfixed64" "bool"
+             "string" "bytes" "group"))
+
+(c-lang-defconst c-modifier-kwds
+  protobuf '("required" "optional" "repeated"))
+
+(c-lang-defconst c-class-decl-kwds
+  protobuf '("message" "enum" "service"))
+
+(c-lang-defconst c-constant-kwds
+  protobuf '("true" "false"))
+
+(c-lang-defconst c-other-decl-kwds
+  protobuf '("package" "import"))
+
+(c-lang-defconst c-other-kwds
+  protobuf '("default" "max"))
+
+(c-lang-defconst c-identifier-ops
+  ;; Handle extended identifiers like google.protobuf.MessageOptions
+  protobuf '((left-assoc ".")))
+
+;; The following keywords do not fit well in keyword classes defined by
+;; cc-mode.  So, we approximate as best we can.
+
+(c-lang-defconst c-type-list-kwds
+  protobuf '("extensions" "to"))
+
+(c-lang-defconst c-typeless-decl-kwds
+  protobuf '("extend" "rpc" "option" "returns"))
+
+
+;; Here we remove default syntax for loops, if-statements and other C
+;; syntactic features that are not supported by the protocol buffer language.
+
+(c-lang-defconst c-brace-list-decl-kwds
+  ;; Remove syntax for C-style enumerations.
+  protobuf nil)
+
+(c-lang-defconst c-block-stmt-1-kwds
+  ;; Remove syntax for "do" and "else" keywords.
+  protobuf nil)
+
+(c-lang-defconst c-block-stmt-2-kwds
+  ;; Remove syntax for "for", "if", "switch" and "while" keywords.
+  protobuf nil)
+
+(c-lang-defconst c-simple-stmt-kwds
+  ;; Remove syntax for "break", "continue", "goto" and "return" keywords.
+  protobuf nil)
+
+(c-lang-defconst c-paren-stmt-kwds
+  ;; Remove special case for the "(;;)" in for-loops.
+  protobuf nil)
+
+(c-lang-defconst c-label-kwds
+  ;; Remove case label syntax for the "case" and "default" keywords.
+  protobuf nil)
+
+(c-lang-defconst c-before-label-kwds
+  ;; Remove special case for the label in a goto statement.
+  protobuf nil)
+
+(c-lang-defconst c-cpp-matchers
+  ;; Disable all the C preprocessor syntax.
+  protobuf nil)
+
+(c-lang-defconst c-decl-prefix-re
+  ;; Same as for C, except it does not match "(". This is needed for disabling
+  ;; the syntax for casts.
+  protobuf "\\([\{\};,]+\\)")
+
+
+;; Add support for variable levels of syntax highlighting.
+
+(defconst protobuf-font-lock-keywords-1 (c-lang-const c-matchers-1 protobuf)
+  "Minimal highlighting for protobuf-mode.")
+
+(defconst protobuf-font-lock-keywords-2 (c-lang-const c-matchers-2 protobuf)
+  "Fast normal highlighting for protobuf-mode.")
+
+(defconst protobuf-font-lock-keywords-3 (c-lang-const c-matchers-3 protobuf)
+  "Accurate normal highlighting for protobuf-mode.")
+
+(defvar protobuf-font-lock-keywords protobuf-font-lock-keywords-3
+  "Default expressions to highlight in protobuf-mode.")
+
+;; Our syntax table is auto-generated from the keyword classes we defined
+;; previously with the `c-lang-const' macro.
+(defvar protobuf-mode-syntax-table nil
+  "Syntax table used in protobuf-mode buffers.")
+(or protobuf-mode-syntax-table
+    (setq protobuf-mode-syntax-table
+          (funcall (c-lang-const c-make-mode-syntax-table protobuf))))
+
+(defvar protobuf-mode-abbrev-table nil
+  "Abbreviation table used in protobuf-mode buffers.")
+
+(defvar protobuf-mode-map nil
+  "Keymap used in protobuf-mode buffers.")
+(or protobuf-mode-map
+    (setq protobuf-mode-map (c-make-inherited-keymap)))
+
+(easy-menu-define protobuf-menu protobuf-mode-map
+  "Protocol Buffers Mode Commands"
+  (cons "Protocol Buffers" (c-lang-const c-mode-menu protobuf)))
+
+;;;###autoload (add-to-list 'auto-mode-alist '("\\.proto\\'" . protobuf-mode))
+
+;;;###autoload
+(defun protobuf-mode ()
+  "Major mode for editing Protocol Buffers description language.
+
+The hook `c-mode-common-hook' is run with no argument at mode
+initialization, then `protobuf-mode-hook'.
+
+Key bindings:
+\\{protobuf-mode-map}"
+  (interactive)
+  (kill-all-local-variables)
+  (set-syntax-table protobuf-mode-syntax-table)
+  (setq major-mode 'protobuf-mode
+        mode-name "Protocol-Buffers"
+        local-abbrev-table protobuf-mode-abbrev-table
+        abbrev-mode t)
+  (use-local-map protobuf-mode-map)
+  (c-initialize-cc-mode t)
+  (c-init-language-vars protobuf-mode)
+  (c-common-init 'protobuf-mode)
+  (easy-menu-add protobuf-menu)
+  (c-run-mode-hooks 'c-mode-common-hook 'protobuf-mode-hook)
+  (c-update-modeline))
+
+(provide 'protobuf-mode)
+
+;;; protobuf-mode.el ends here