Chapter 23. Customizing Filetype Detection and Actions


See the tutorial for a simple example how to define a new filetype.



FILETYPE DETECTION

A-A-P detects the type of a file automatically.  This is used to decide
what tools can be used for a certain file.

To manually set the file type of an item add the "filetype" attribute.  This
overrules the automatic detection.
Example:
	foo.o : foo.x {filetype = cpp}

Most detection is already built in.  If this is not sufficient for your work,
filetype detection instructions can be used to change the way file type
detection works.  These instructions can either be in a file or directly in
the recipe:

	:filetype  filename
	:filetype
		suffix p pascal
		script .*bash$ sh
	
The advantage of using a file is that it will also be possible to use it when
running the filetype detection as a separate program.  The advantage of using
the instructions directly in the recipe is that you don't have to create
another file.

For the syntax of the file see filetype.txt.

It is sometimes desired to handle a group of files in a different way.  For
example, to use a different optimizer setting when compiling C files.  An easy
way to do this is to give these files a different filetype.  Then define a
compile action specifically for this filetype.  Example:

	:attr {filetype = c_opt} bar.c foo.c
	:action compile c_opt
		CFLAGS = -O3
		:do compile $source

The detected filetypes never contain an underscore.  A-A-P knows that the
underscore separates the normal filetype from the additional part.  When no
action is found for the whole filetype, it is tried by removing the "_" and
what comes after it.  (This isn't fully implemented yet!)

Care should be taken that an action should not invoke itself.  For example, to
always compile "version.c" when linking a program:

	:attr {filetype = my_prog} $TARGET
	:action build my_prog object
		:do compile {target = version$OBJSUF} version.c
		:do build {target = $target {filetype = program}}
					$source version$OBJSUF

Without "{filetype = program}" on the :do build" command, the action would
invoke itself, since the filetype for $TARGET is "my_prog".


EXECUTING ACTIONS

The user can select how to perform an action for each type of file.  For
example, the user may specify that the "view" action on a file of type "html"
uses Netscape, and the "edit" action on a "html" file uses Vim.

To start an application:

	:do action filename

This starts the "action" application for file "filename".
Attributes for the commands can be specified after the action:

	:do action {arg = -r} filename

The filetype is automatically detected from the file name and possibly its
contents.  Extra suffixes like ".in" and ".gz" are ignored.
To overrule the automatic filetype detection, specify the filetype as an
attribute on the file:

	:do action filename {filetype = text}

Multiple filename arguments can be used:

	:do action file1 file2 file3

For some actions a target can or must be specified.  This is done as an
attribute on the action:

	:do action {target = outfile} infile1 infile2

Attributes of the filenames other than "filetype" are not used!

The "async" attribute can be used to start the application without waiting for
it to finish.  However, this only works for system commands and when
multi-tasking is possible.  Example:

	:do email {async} {remove} {to = piet} {subject = done building} logmessage

The "remove" attribute specifies that the files are to be deleted after the
command is done, also when it fails.

When the filetype contains a "_" and no action can be found for it, the search
for an action is done with the part before the "_".  This is useful for
specifying a variant on a filetype where some commands are different and the
rest is the same.

"action" is usually one of these:

	view		Look at the file.  The "readonly" attribute is
			normally set, it can be reset to allow editing.
	edit		Edit the file.
	email		Send the file by e-mail.  Relevant attributes:
			    edit	edit before sending
			    subject	subject of the message
			    to		destination
	build		Build the file(s), resulting in a program file.  The
			"target" attribute is needed to specify the output
			file.

	compile		Build the file(s), resulting in object file(s).
			The "target" attribute may be used to specify the
			output file.  When "target" is not specified the
			action may use a default, usually $BDIR/root$OBJSUF.
	
	extract		Unpack an archive.  Requires the program for unpacking
			to be available.  Unpacks in the current directory.

	preproc		Run the preprocessor on the file.  The "target"
			attribute can be used to specify the output file.
			When it is missing the output file name is formed from
			the input file name by using the ".i" suffix.

	reference	Run a cross referencer, creating or updating a symbol
			database.
	
	strip		Strip symbols from a program.  Used to make it smaller
			after installing.

Examples:

	:do view COPYRIGHT {filetype = text}
	:do edit configargs.xml
	:do email {edit} bugreport
	:do build {target = myprog} main.c version.c
	:do compile foo.cpp


Default actions:

These are defined in the default.aap recipe.  TODO: update this info

:action edit default
	Uses the environment variable $VISUAL or $EDITOR.  Falls back to "vi"
	for Posix systems or "notepad" otherwise

:action view html,xml,php
	Uses the environment variable $BROWSER.  Searches a list of known
	browsers if it's not set.

:action email default
	Uses the environment variable $MAILER.  Falls back to "mail".

:action build default default
    	Does: ":sys $CC $LDFLAGS $CFLAGS -o $target $source $?LIBS"

:action compile object c,cpp
    	Does ":sys $CC $CPPFLAGS $CFLAGS -c -o $target" $source

:action preproc default c,cpp
    	Does ":sys $CC $CPPFLAGS -E $source > $target"


Specifying actions:

Applications for an action-filetype pair can be specified with this command:

	:action action in-filetype
		commands

This associates the commands with action "action" and filetype "in-filetype".
The commands are A-A-P commands, just like what is used in the build commands
in a dependency.

The "in-filetype" is used for the source of the action, the type of the target
is undefined.  It is also possible to specify an action for turning a file of
one filetype into another filetype.  This is like a ":rule" command, but using
filetypes instead of patterns.

	:action action out-filetype in-filetype
		commands

Actually, specifying an action with one filetype is like using "default" for
the out-filetype.

Several variables are set and can be used by the commands:
	$fname		The first file name of the ":do" command.
	$source		All the file names of the ":do" command.
	$filetype	The detected or specified filetype for the input.
	$targettype	The detected or specified filetype for the output.
	$action		The name of the action for which the commands are
			executed.

Furthermore, all attributes of the action are turned into variables.  Thus
when ":do action {arg = -x} file " is used, $arg is set to "-x".  Example for
using an optional "arg" attribute:

	:action view foo
		:sys fooviewer $?arg $source

In Python code check if the {edit} attribute is specified:

	:action email default
		# when $subject and/or $to is missing editing is required
		@if not globals().get("subject") or not globals().get("to"):
		    edit = 1
		@if globals().get("edit"):
		    :do edit $fname
		:sys mail -s $subject $to < $fname

"action" and "ftype" can also be a comma-separated list of filetypes.  There
can't be any white space though.  Examples:

	:action view html,xml,php
		:sys netscape --remote $source
	:action edit,view text,c,cpp
		:sys vim $source

"filetype" can be "default" to specify an action used when there is no action
specifically for the filetype.

Note that the "async" attribute of the ":do" command may cause the ":sys"
command to work asynchronously.  That is done because the "async" attribute is
turned into the "async" variable for the ":action" commands.  If you don't
want a specific ":sys" command to work asynchronously, reset "async":

	:action view foo
		tt = $?async
		async = 
		:sys foo_prepare
		async = $tt
		:sys foo $source

However, since two consecutive ":sys" commands are executed together, this
should do the same thing:

	:action view foo
		:sys foo_prepare
		:sys foo $source

Quite often the program to be used depends on whether it is available on the
system.  For example, viewing HTML files can be done with netscape, mozilla,
konquerer or another browser.  We don't want to search the system for all
kinds of programs when starting, it would make the startup time quite long.
And we don't want to search each time the action is invoked, the result of the
first search can be used.  This construct can be used to achieve this:

	BROWSER =
	:action view html
	    @if not BROWSER:
		:progsearch BROWSER netscape mozilla konquerer
	    :sys $BROWSER $source
	    :export BROWSER

The generic form form :progsearch is:

	:progsearch varname progname ...

":export" needs to be used for variables set in the commands and need to be
used after the action is finished.

The first argument is the variable name to which to assign the resulting
program name.  When none of the programs is found an error message is given.
Note that shell aliases are not found, only executable programs.

More examples:
	:action compile c,cpp
		:sys $CC $CPPFLAGS $CFLAGS -c $source
	:action build object
		:sys $CC $LDFLAGS $CFLAGS -o $target $source