Emacs, a performant IDE for Perl

Emacs, a performant IDE for Perl Tutorial for YAPC.:EU:::2009, Lisbon [email_address] Département Office

Overview
Intended audience
Emacs newcomers
[ seasoned Emacs users … may find some additional tips ]
curious …
Topics
Intro
Emacs concepts
General editing
Perl programming
External tools
Emacs-Perl integration : extension packages

What is Emacs ?
"Emacs is the extensible, customizable, self-documenting real-time display editor".
advanced : provides much more than simple insertion and deletion. It can control subprocesses, indent programs automatically, show two or more files at once, and edit formatted text.
self-documenting : can type C-h at any time to find out what the options are.
customizable : thousands of variables
extensible : internal Lisp interpreter
feature-rich : thousands of commands

Emacs history
early 1970s : initial work on PDP computers (MIT Labs)
1976 : first release
1981 : Gosling Emacs on Unix
1986 : GNU Emacs 15.34
1991 : XEmacs fork (formerly Lucid Emacs)
2008: GNU Emacs 22.3

Emacs main concepts
buffer : basic editing unit (text being edited). Can be bound to various contents like :
file (local/remote)
computed content (listings, compilation results, shell, email, etc.)
external process
window : screen area for displaying buffer content
frame : OS window
mode : set of options for editing some kind of content
major mode : mutually exclusive
minor mode : additional options (plugin)

Other concepts
region : portion of buffer between mark and point
rectangle : rectangular area instead of linear text
register : memory for storing text / position / rectangle
macro : recorded sequence of keys
desktop : saved Emacs session

User input
Input events
character events
modifiers : <CTRL>, <ALT>, <META>, <SUPER>
mouse, scroll, click, focus, etc.
Key sequence
prefix key  keymap. Ex:
C-x General extended commands
C-h Help commands
C-c Mode-specific extended commands
complete key  command
Keymap
binding key  command
global / local

Entering commands/args in minibuffer
Auto-completion
Default argument
Editing (cut/paste/move/etc.)
Command history

Modes may implement …
additional commands
local implementation for generic operations
ex: comment-region, indent-region
syntax highlighting
local keymaps
local menus
modifications to the display (ex. status line)
hooks

Editing
Move
by character, word, sentence, paragraph, page
Copy / Cut / Paste
kill ring : history of killed fragments
Search / Replace
incremental / regex
word search (without regard to punctuation)
clever case substitutions
recursive edit
Abbrevs
Undo

Files
File names / completion / disambiguation
Remote files (ange-ftp / tramp)
Archives / compressed files
Mode chosen automatically from name or content
Bookmarks (filename / position / comment)
Shadowing (automatic replication)
Filesets

Editing directories
listing
create / rename / delete
bulk operations (mark / regexp )
open subdirectories in same buffer
chmod, mkdir, etc.
exec shell command on file(s)

Shell
Inferior process
filename completion
history ring
editing command-line
directory tracking
remote host (telnet, rlogin, etc)
Eshell
no process, all done in Emacs

Help
Info (manual)
Help on
variables
functions
keys
bindings
mode
apropos

Programming modes : generic features
Recognize top-level definitions
go to begin / end, set region (C-M-h), imenu
Indentation
clever syntax parsing; various indent styles (K&R, BSD, Gnu, etc.)
Balanced parentheses
begin / end, up / down, kill,
(C-M-LEFT, C-M-UP, ..)
blink-matching
Comments
insert, realign, comment / uncomment region, reformat
Syntax highlighing
Restricting editing scope
hideshow minor mode
narrowing
(C-x n d / w)
Autocompletion
Electric characters
automatic reindent / newline
Tags support

Cperl mode
based on C-mode
indenting
electric parentheses
automatic expansion (if, else, while, do, foreach, …)
syntax highlighting
binding to perlinfo
menu, tools
perldb : gud bindings
next / step
break (C-x SP)

Compiling and testing
Compilation
launch compiler subprocess ("perl", "gcc", "make", etc.)
mod-compile.el : additional layer
adapt compilation command to current language / context
parse errors and navigate to source files
usual Emacs commands for viewing results / debug logs
GUD (Grand Unified Debugger)
shell buffer
navigate to source files

Searching
builtin support for "grep"
ack.el : adaptation for "ack"
navigate in matched files like for the compilation buffer

Autocompletion
Static sources
Tags
Language-specific doc
More context-aware
Emacs extensions : Sepia, PerlySense
Dabbrev
most recent, preceding word for which this is a prefix
if none, search following words
if none, search other "friend" buffers
Hippie-expand
ring of try functions
try-complete-file-name
try-expand-all-abbrevs
try-expand-line
try-expand-dabbrev
try-expand-whole-kill

External filters
Ex: perltidy
; tidy perl code on region
(defun perltidy ()
"run perltidy on the current region or buffer."
(interactive)
(shell-command-on-region (point) (mark)
"perltidy -q" nil t))
(global-set-key "C-ct" 'perltidy)

Version control
generic version control (VC)
psvn.el : SVN support
status
dired-like
log
ediff
similar modes for git

Differences / patches
ediff-mode
both versions side-by-side (horizontal or vertical)
ediff commands
previous / next
copy A  B / B  A
apply patches (multifiles OK)

perlcritic
mode perlcritic.el distributed with Perl::Critic
apply on buffer
apply on region
parse output
other solution: treat as a standard compile command
must configure .perlcriticrc so that Emacs understands filenames
verbose = %f:%l:%c: %m, %e (%p, severity %s)

Emacs::EPL
Perl-Emacs IPC integration, followup to "Perlmacs"
looks like this was very nice work
adapted environment for running Perl under Emacs
redefine STDIN, STDOUT as hooks to Emacs minibuffer
populate ENV
…
can write Emacs modules in Perl instead of elisp !
last distribution dates back to 2001, using Perl 5.004
couldn't get it to work 

Devel::PerlySense
Perl process in the background
Lots of features
links to doc
class hierarchy analysis and method analysis
jump to definition / class
run / debug
run tests
interact with ack
notion of "project"
file templates
but very CPU-intensive and slow 

Sepia
last distrib May 09
Inspired by Emacs Lisp dev. philosophy
Features
completion on partial words, i.e. L:U  List::Util
inferior Perl process with REPL loop
analyses opcodes
links to doc, to func definitions, to modules
 only recognizes core modules/functions
didn't figure how to let it read perl/site/lib !

Emacs::PDE
last distrib July 2008
Features (pde-load)
projects
smart compile (C-c r) / debug
tags / menus / tree view (C-c C-v TAB)
perldoc integration with browser (C-c C-v RET, C-c C-v C-p)
special indenting mode
integrate with perltidy / perlcritic
interactive perl shell
 no install problems
need to learn more

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Emacs, a performant IDE for Perl

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