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[gnu-emacs] / doc / misc / flymake.texi

\input texinfo   @c -*-texinfo-*-
@comment %**start of header
@setfilename ../../info/flymake
@set VERSION 0.3
@set UPDATED April 2004
@settitle GNU Flymake @value{VERSION}
@syncodeindex pg cp
@comment %**end of header

@copying
This manual is for GNU Flymake (version @value{VERSION}, @value{UPDATED}),
which is a universal on-the-fly syntax checker for GNU Emacs.

Copyright @copyright{} 2004, 2005, 2006, 2007, 2008 Free Software
Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover texts being ``A GNU Manual,''
and with the Back-Cover Texts as in (a) below.  A copy of the license
is included in the section entitled ``GNU Free Documentation License''.

(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
modify this GNU manual.  Buying copies from the FSF supports it in
developing GNU and promoting software freedom.''
@end quotation
@end copying

@dircategory Emacs
@direntry
* Flymake: (flymake). A universal on-the-fly syntax checker.
@end direntry

@titlepage
@title GNU Flymake
@subtitle for version @value{VERSION}, @value{UPDATED}
@author Pavel Kobiakov(@email{pk_at_work@@yahoo.com})
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@ifnottex
@node Top
@top GNU Flymake
@end ifnottex

@menu
* Overview of Flymake::
* Installing Flymake::
* Using Flymake::
* Configuring Flymake::
* Flymake Implementation::
* GNU Free Documentation License::
* Index::
@end menu

@node Overview of Flymake
@chapter Overview
@cindex Overview of Flymake

Flymake is a universal on-the-fly syntax checker implemented as an
Emacs minor mode. Flymake runs the pre-configured syntax check tool
(compiler for C++ files, @code{perl} for perl files, etc.) in the
background, passing it a temporary copy of the current buffer, and
parses the output for known error/warning message patterns. Flymake
then highlights erroneous lines (i.e. lines for which at least one
error or warning has been reported by the syntax check tool), and
displays an overall buffer status in the mode line. Status information
displayed by Flymake contains total number of errors and warnings
reported for the buffer during the last syntax check.

@code{flymake-goto-next-error} and @code{flymake-goto-prev-error}
functions allow for easy navigation to the next/previous erroneous
line, respectively.

Calling @code{flymake-display-err-menu-for-current-line} will popup a
menu containing error messages reported by the syntax check tool for
the current line. Errors/warnings belonging to another file, such as a
@code{.h} header file included by a @code{.c} file, are shown in the
current buffer as belonging to the first line. Menu items for such
messages also contain a filename and a line number. Selecting such a
menu item will automatically open the file and jump to the line with
error.

Syntax check is done 'on-the-fly'. It is started whenever

@itemize @bullet
@item buffer is loaded
@item a newline character is added to the buffer
@item some changes were made to the buffer more than @code{0.5} seconds ago (the
delay is configurable).
@end itemize

Flymake is a universal syntax checker in the sense that it's easily
extended to support new syntax check tools and error message
patterns. @xref{Configuring Flymake}.

@node Installing Flymake
@chapter Installing
@cindex Installing Flymake


Flymake is packaged in a single file, @code{flymake.el}.

To install/update Flymake, place @code{flymake.el} to a directory
somewhere on Emacs load path. You might also want to byte-compile
@code{flymake.el} to improve performance.

Also, place the following line in the @code{.emacs} file.

@lisp
(require 'flymake)
@end lisp

You might also map the most frequently used Flymake functions, such as
@code{flymake-goto-next-error}, to some keyboard shortcuts:

@lisp
(global-set-key [f3] 'flymake-display-err-menu-for-current-line)
(global-set-key [f4] 'flymake-goto-next-error)
@end lisp

@node Using Flymake
@chapter Using Flymake
@cindex Using Flymake

@menu
* Flymake mode::
* Running the syntax check::
* Navigating to error lines::
* Viewing error messages::
* Syntax check statuses::
* Troubleshooting::
@end menu

@node Flymake mode
@section Flymake mode
@cindex flymake-mode

Flymake is an Emacs minor mode. To use Flymake, you
must first activate @code{flymake-mode} by using the
@code{flymake-mode} function.

Instead of manually activating @code{flymake-mode}, you can configure
Flymake to automatically enable @code{flymake-mode} upon opening any
file for which syntax check is possible. To do so, place the following
line in @code{.emacs}:

@lisp
(add-hook 'find-file-hook 'flymake-find-file-hook)
@end lisp

@node Running the syntax check
@section Running the syntax check
@cindex Manually starting the syntax check

When @code{flymake-mode} is active, syntax check is started
automatically on any of the three conditions mentioned above. Syntax
check can also be started manually by using the
@code{flymake-start-syntax-check-for-current-buffer} function. This
can be used, for example, when changes were made to some other buffer
affecting the current buffer.

@node Navigating to error lines
@section Navigating to error lines
@cindex Navigating to error lines

After syntax check is completed, lines for which at least one error or
warning has been reported are highlighted, and total number of errors
and warning is shown in the mode line. Use the following functions to
navigate the highlighted lines.

@multitable @columnfractions 0.25 0.75

@item @code{flymake-goto-next-error}
@tab Moves point to the next erroneous line, if any.

@item @code{flymake-goto-prev-error}
@tab Moves point to the previous erroneous line.

@end multitable

These functions treat erroneous lines as a linked list. Therefore,
@code{flymake-goto-next-error} will go to the first erroneous line
when invoked in the end of the buffer.

@node Viewing error messages
@section Viewing error messages
@cindex Viewing error messages

To view error messages belonging to the current line, use the
@code{flymake-display-err-menu-for-current-line} function. If there's
at least one error or warning reported for the current line, this
function will display a popup menu with error/warning texts.
Selecting the menu item whose error belongs to another file brings
forward that file with the help of the
@code{flymake-goto-file-and-line} function.

@node Syntax check statuses
@section Syntax check statuses
@cindex Syntax check statuses

After syntax check is finished, its status is displayed in the mode line.
The following statuses are defined.

@multitable @columnfractions 0.25 0.75
@item Flymake* or Flymake:E/W*
@tab  Flymake is currently running. For the second case, E/W contains the
      error and warning count for the previous run.

@item Flymake
@tab  Syntax check is not running. Usually this means syntax check was
      successfully passed (no errors, no warnings). Other possibilities are:
      syntax check was killed as a result of executing
      @code{flymake-compile}, or syntax check cannot start as compilation
      is currently in progress.

@item Flymake:E/W
@tab  Number of errors/warnings found by the syntax check process.

@item Flymake:!
@tab  Flymake was unable to find master file for the current buffer.
@end multitable

The following errors cause a warning message and switch flymake mode
OFF for the buffer.

@multitable @columnfractions 0.25 0.75
@item CFGERR
@tab  Syntax check process returned nonzero exit code, but no
      errors/warnings were reported. This indicates a possible configuration
      error (for example, no suitable error message patterns for the
      syntax check tool).

@item NOMASTER
@tab  Flymake was unable to find master file for the current buffer.

@item NOMK
@tab  Flymake was unable to find a suitable buildfile for the current buffer.

@item PROCERR
@tab  Flymake was unable to launch a syntax check process.
@end multitable


@node Troubleshooting
@section Troubleshooting
@cindex Logging
@cindex Troubleshooting

Flymake uses a simple logging facility for indicating important points
in the control flow. The logging facility sends logging messages to
the @code{*Messages*} buffer. The information logged can be used for
resolving various problems related to Flymake.

Logging output is controlled by the @code{flymake-log-level}
variable. @code{3} is the  most verbose level, and @code{-1} switches
logging off.

@node Configuring Flymake
@chapter Configuring and Extending Flymake
@cindex Configuring and Extending Flymake

@menu
* Customizable variables::
* Adding support for a new syntax check tool::
@end menu

Flymake was designed to be easily extended for supporting new syntax
check tools and error message patterns.

@node Customizable variables
@section Customizable variables
@cindex Customizable variables

This section summarizes variables used for Flymake
configuration.

@table @code
@item flymake-log-level
Controls logging output, see @ref{Troubleshooting}.

@item flymake-allowed-file-name-masks
A list of @code{(filename-regexp, init-function, cleanup-function
getfname-function)} for configuring syntax check tools. @xref{Adding
support for a new syntax check tool}.

@item flymake-buildfile-dirs
A list of directories (relative paths) for searching a
buildfile. @xref{Locating the buildfile}.

@item flymake-master-file-dirs
A list of directories for searching a master file. @xref{Locating a
master file}.

@item flymake-get-project-include-dirs-function
A function used for obtaining a list of project include dirs (C/C++
specific). @xref{Getting the include directories}.

@item flymake-master-file-count-limit
@itemx flymake-check-file-limit
Used when looking for a master file. @xref{Locating a master file}.

@item flymake-err-line-patterns
Patterns for error/warning messages in the form @code{(regexp file-idx
line-idx col-idx err-text-idx)}. @xref{Parsing the output}.

@item flymake-compilation-prevents-syntax-check
A flag indicating whether compilation and syntax check of the same
file cannot be run simultaneously.

@item flymake-no-changes-timeout
If any changes are made to the buffer, syntax check is automatically
started after @code{flymake-no-changes-timeout} seconds.

@item flymake-gui-warnings-enabled
A boolean flag indicating whether Flymake will show message boxes for
non-recoverable errors. If @code{flymake-gui-warnings-enabled} is
@code{nil}, these errors will only be logged to the @code{*Messages*}
buffer.

@item flymake-start-syntax-check-on-newline
A boolean flag indicating whether to start syntax check after a
newline character is added to the buffer.

@item flymake-errline
A custom face for highlighting lines for which at least one error has
been reported.

@item flymake-warnline
A custom face for highlighting lines for which at least one warning
and no errors have been reported.

@end table

@node Adding support for a new syntax check tool
@section Adding support for a new syntax check tool
@cindex Adding support for a new syntax check tool

@menu
* Example -- Configuring a tool called directly::
* Example -- Configuring a tool called via make::
@end menu

Syntax check tools are configured using the
@code{flymake-allowed-file-name-masks} list. Each item of this list
has the following format:

@lisp
(filename-regexp, init-function, cleanup-function, getfname-function)
@end lisp

@table @code
@item filename-regexp
This field is used as a key for locating init/cleanup/getfname
functions for the buffer.  Items in
@code{flymake-allowed-file-name-masks} are searched sequentially. The
first item with @code{filename-regexp} matching buffer filename is
selected. If no match is found, @code{flymake-mode} is switched off.

@item init-function
@code{init-function} is required to initialize the syntax check,
usually by creating a temporary copy of the buffer contents. The
function must return @code{(list cmd-name arg-list)}. If
@code{init-function} returns null, syntax check is aborted, by
@code{flymake-mode} is not switched off.

@item cleanup-function
@code{cleanup-function} is called after the syntax check process is
complete and should take care of proper deinitialization, which is
usually deleting a temporary copy created by the @code{init-function}.

@item getfname-function
This function is used for translating filenames reported by the syntax
check tool into ``real'' filenames. Filenames reported by the tool
will be different from the real ones, as actually the tool works with
the temporary copy.  In most cases, the default implementation
provided by Flymake, @code{flymake-get-real-file-name}, can be used as
@code{getfname-function}.

@end table

To add support for a new syntax check tool, write corresponding
@code{init-function}, and, optionally @code{cleanup-function} and
@code{getfname-function}.  If the format of error messages reported by
the new tool is not yet supported by Flymake, add a new entry to
the @code{flymake-err-line-patterns} list.

The following sections contain some examples of configuring Flymake
support for various syntax check tools.

@node Example -- Configuring a tool called directly
@subsection Example -- Configuring a tool called directly
@cindex Adding support for perl

In this example, we will add support for @code{perl} as a syntax check
tool. @code{perl} supports the @code{-c} option which does syntax
checking.

First, we write the @code{init-function}:

@lisp
(defun flymake-perl-init ()
  (let* ((temp-file (flymake-init-create-temp-buffer-copy
                     'flymake-create-temp-inplace))
         (local-file (file-relative-name
                      temp-file
                      (file-name-directory buffer-file-name))))
    (list "perl" (list "-wc " local-file))))
@end lisp

@code{flymake-perl-init} creates a temporary copy of the buffer
contents with the help of
@code{flymake-init-create-temp-buffer-copy}, and builds an appropriate
command line.

Next, we add a new entry to the
@code{flymake-allowed-file-name-masks}:

@lisp
(setq flymake-allowed-file-name-masks
      (cons '(".+\\.pl$"
              flymake-perl-init
              flymake-simple-cleanup
              flymake-get-real-file-name)
            flymake-allowed-file-name-masks))
@end lisp

Note that we use standard @code{cleanup-function} and
@code{getfname-function}.

Finally, we add an entry to @code{flymake-err-line-patterns}:

@lisp
(setq flymake-err-line-patterns
      (cons '("\\(.*\\) at \\([^ \n]+\\) line \\([0-9]+\\)[,.\n]"
              2 3 nil 1)
            flymake-err-line-patterns))
@end lisp

@node Example -- Configuring a tool called via make
@subsection Example -- Configuring a tool called via make
@cindex Adding support for C (gcc+make)

In this example we will add support for C files syntax checked by
@code{gcc} called via @code{make}.

We're not required to write any new functions, as Flymake already has
functions for @code{make}. We just add a new entry to the
@code{flymake-allowed-file-name-masks}:

@lisp
(setq flymake-allowed-file-name-masks
      (cons '(".+\\.c$"
              flymake-simple-make-init
              flymake-simple-cleanup
              flymake-get-real-file-name)
            flymake-allowed-file-name-masks))
@end lisp

@code{flymake-simple-make-init} builds the following @code{make}
command line:

@lisp
(list "make"
      (list "-s" "-C"
            base-dir
            (concat "CHK_SOURCES=" source)
            "SYNTAX_CHECK_MODE=1"
            "check-syntax"))
@end lisp

@code{base-dir} is a directory containing @code{Makefile}, see @ref{Locating the buildfile}.

Thus, @code{Makefile} must contain the @code{check-syntax} target. In
our case this target might look like this:

@verbatim
check-syntax:
        gcc -o nul -S ${CHK_SOURCES}
@end verbatim

The format of error messages reported by @code{gcc} is already
supported by Flymake, so we don't have to add a new entry to
@code{flymake-err-line-patterns}.

@node Flymake Implementation
@chapter Flymake Implementation
@cindex Implementation details

@menu
* Determining whether syntax check is possible::
* Making a temporary copy::
* Locating a master file::
* Getting the include directories::
* Locating the buildfile::
* Starting the syntax check process::
* Parsing the output::
* Highlighting erroneous lines::
* Interaction with other modes::
@end menu

Syntax check is started by calling @code{flymake-start-syntax-check-for-current-buffer}.
Flymake first determines whether it is able to do syntax
check. It then saves a copy of the buffer in a temporary file in the
buffer's directory (or in the system temp directory -- for java
files), creates a syntax check command and launches a process with
this command. The output is parsed using a list of error message patterns,
and error information (file name, line number, type and text) is
saved. After the process has finished, Flymake highlights erroneous
lines in the buffer using the accumulated error information.

@node Determining whether syntax check is possible
@section Determining whether syntax check is possible
@cindex Syntax check models
@cindex Master file

Syntax check is considered possible if there's an entry in
@code{flymake-allowed-file-name-masks} matching buffer's filename and
its @code{init-function} returns non-@code{nil} value.

Two syntax check modes are distinguished:

@enumerate

@item
Buffer can be syntax checked in a standalone fashion, that is, the
file (its temporary copy, in fact) can be passed over to the compiler to
do the syntax check. Examples are C/C++ (.c, .cpp) and Java (.java)
sources.

@item
Buffer can be syntax checked, but additional file, called master file,
is required to perform this operation. A master file is a file that
includes the current file, so that running a syntax check tool on it
will also check syntax in the current file. Examples are C/C++ (.h,
.hpp) headers.

@end enumerate

These modes are handled inside init/cleanup/getfname functions, see
@ref{Adding support for a new syntax check tool}.

Flymake contains implementations of all functionality required to
support different syntax check modes described above (making
temporary copies, finding master files, etc.), as well as some
tool-specific (routines for @code{make}, @code{Ant}, etc.) code.


@node Making a temporary copy
@section Making a temporary copy
@cindex Temporary copy of the buffer
@cindex Master file

After the possibility of the syntax check has been determined, a
temporary copy of the current buffer is made so that the most recent
unsaved changes could be seen by the syntax check tool. Making a copy
is quite straightforward in a standalone case (mode @code{1}), as it's
just saving buffer contents to a temporary file.

Things get trickier, however, when master file is involved, as it
requires to

@itemize @bullet
@item locate a master file
@item patch it to include the current file using its new (temporary)
name.
@end itemize

Locating a master file is discussed in the following section.

Patching just changes all appropriate lines of the master file so that they
use the new (temporary) name of the current file. For example, suppose current
file name is @code{file.h}, the master file is @code{file.cpp}, and
it includes current file via @code{#include "file.h"}. Current file's copy
is saved to file @code{file_flymake.h}, so the include line must be
changed to @code{#include "file_flymake.h"}. Finally, patched master file
is saved to @code{file_flymake_master.cpp}, and the last one is passed to
the syntax check tool.

@node Locating a master file
@section Locating a master file
@cindex Master file

Master file is located in two steps.

First, a list of possible master files is built. A simple name
matching is used to find the files. For a C++ header @code{file.h},
Flymake searches for all @code{.cpp} files in the directories whose relative paths are
stored in a customizable variable @code{flymake-master-file-dirs}, which
usually contains something like @code{("." "./src")}. No more than
@code{flymake-master-file-count-limit} entries is added to the master file
list. The list is then sorted to move files with names @code{file.cpp} to
the top.

Next, each master file in a list is checked to contain the appropriate
include directives. No more than @code{flymake-check-file-limit} of each
file are parsed.

For @code{file.h}, the include directives to look for are
@code{#include "file.h"}, @code{#include "../file.h"}, etc. Each
include is checked against a list of include directories
(see @ref{Getting the include directories}) to be sure it points to the
correct @code{file.h}.

First matching master file found stops the search. The master file is then
patched and saved to disk. In case no master file is found, syntax check is
aborted, and corresponding status (!) is reported in the mode line.

@node Getting the include directories
@section Getting the include directories
@cindex Include directories (C/C++ specific)

Two sets of include directories are distinguished: system include directories
and project include directories. The former is just the contents of the
@code{INCLUDE} environment variable. The latter is not so easy to obtain,
and the way it can be obtained can vary greatly for different projects.
Therefore, a customizable variable
@code{flymake-get-project-include-dirs-function} is used to provide the
way to implement the desired behavior.

The default implementation, @code{flymake-get-project-include-dirs-imp},
uses a @code{make} call. This requires a correct base directory, that is, a
directory containing a correct @code{Makefile}, to be determined.

As obtaining the project include directories might be a costly operation, its
return value is cached in the hash table. The cache is cleared in the beginning
of every syntax check attempt.

@node Locating the buildfile
@section Locating the buildfile
@cindex Locating the buildfile
@cindex buildfile, locating
@cindex Makefile, locating

Flymake can be configured to use different tools for performing syntax
checks. For example, it can use direct compiler call to syntax check a perl
script or a call to @code{make} for a more complicated case of a
@code{C/C++} source. The general idea is that simple files, like perl
scripts and html pages, can be checked by directly invoking a
corresponding tool. Files that are usually more complex and generally
used as part of larger projects, might require non-trivial options to
be passed to the syntax check tool, like include directories for
C++. The latter files are syntax checked using some build tool, like
@code{make} or @code{Ant}.

All @code{make} configuration data is usually stored in a file called
@code{Makefile}. To allow for future extensions, flymake uses a notion of
buildfile to reference the 'project configuration' file.

Special function, @code{flymake-find-buildfile} is provided for locating buildfiles.
Searching for a buildfile is done in a manner similar to that of searching
for possible master files. A customizable variable
@code{flymake-buildfile-dirs} holds a list of relative paths to the
buildfile. They are checked sequentially until a buildfile is found. In case
there's no build file, syntax check is aborted.

Buildfile values are also cached.

@node Starting the syntax check process
@section Starting the syntax check process
@cindex Syntax check process

The command line (command name and the list of arguments) for launching a process is returned by the
initialization function. Flymake then just calls @code{start-process}
to start an asynchronous process and configures process filter and
sentinel which is used for processing the output of the syntax check
tool.

@node Parsing the output
@section Parsing the output
@cindex Parsing the output

The output generated by the syntax check tool is parsed in the process
filter/sentinel using the error message patterns stored in the
@code{flymake-err-line-patterns} variable. This variable contains a
list of items of the form @code{(regexp file-idx line-idx
err-text-idx)}, used to determine whether a particular line is an
error message and extract file name, line number and error text,
respectively. Error type (error/warning) is also guessed by matching
error text with the '@code{^[wW]arning}' pattern. Anything that was not
classified as a warning is considered an error. Type is then used to
sort error menu items, which shows error messages first.

Flymake is also able to interpret error message patterns missing err-text-idx
information. This is done by merely taking the rest of the matched line
(@code{(substring line (match-end 0))}) as error text. This trick allows
to make use of a huge collection of error message line patterns from
@code{compile.el}. All these error patterns are appended to
the end of @code{flymake-err-line-patterns}.

The error information obtained is saved in a buffer local
variable. The buffer for which the process output belongs is
determined from the process-id@w{}->@w{}buffer mapping updated
after every process launch/exit.

@node Highlighting erroneous lines
@section Highlighting erroneous lines
@cindex Erroneous lines, faces

Highlighting is implemented with overlays and happens in the process
sentinel, after calling the cleanup function. Two customizable faces
are used: @code{flymake-errline} and
@code{flymake-warnline}.  Errors belonging outside the current
buffer are considered to belong to line 1 of the current buffer.

@node Interaction with other modes
@section Interaction with other modes
@cindex Interaction with other modes
@cindex Interaction with compile mode

The only mode flymake currently knows about is @code{compile}.

Flymake can be configured to not start syntax check if it thinks the
compilation is in progress. The check is made by the
@code{flymake-compilation-is-running}, which tests the
@code{compilation-in-progress} variable. The reason why this might be
useful is saving CPU time in case both syntax check and compilation
are very CPU intensive. The original reason for adding this feature,
though, was working around a locking problem with MS Visual C++ compiler.

Flymake also provides an alternative command for starting compilation,
@code{flymake-compile}:

@lisp
(defun flymake-compile ()
  "Kill all flymake syntax checks then start compilation."
  (interactive)
  (flymake-stop-all-syntax-checks)
  (call-interactively 'compile))
@end lisp

It just kills all the active syntax check processes before calling
@code{compile}.

@node GNU Free Documentation License
@appendix GNU Free Documentation License
@include doclicense.texi

@node Index
@unnumbered Index

@printindex cp

@bye

@ignore
   arch-tag: 9f0db077-5598-49ab-90b9-8df9248a63ec
@end ignore