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bitbake: bitbake-user-manual: Added examples for using overrides with functions. 

Fixes [YOCTO #10296]

This adds some bits clarifying you can append and prepend to
functions.  Added a bit to the introduction paragraph of the
"Appending and Prepending (Override Style Syntax)" section to
note that you can do this.  Referenced some new examples.

In the "Shell Functions" section I added an example.  In the
"BitBake Style Python Functions" section I also added an example.

(Bitbake rev: 6e6b7e10e04fdb94b59bd2ead3ccb79c899c7458)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark 2016-09-21 15:30:14 -07:00 committed by Richard Purdie
parent dda8ed0662
commit 7ab459d4b5
1 changed files with 103 additions and 12 deletions
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115
bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
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@ -277,6 +277,15 @@
override syntax.
</note>
</para>
<para>
It is also possible to append and prepend to shell
functions and BitBake-style Python functions.
See the
"<link linkend='shell-functions'>Shell Functions</link>" and
"<link linkend='bitbake-style-python-functions'>BitBake Style Python Functions</link>
sections for examples.
</para>
</section>
<section id='removing-override-style-syntax'>
@ -1090,6 +1099,56 @@
such as <filename>dash</filename>.
You should not use Bash-specific script (bashisms).
</para>
<para>
Overrides and override-style operators like
<filename>_append</filename> and
<filename>_prepend</filename> can also be applied to
shell functions.
Most commonly, this application would be used in a
<filename>.bbappend</filename> file to modify functions in
the main recipe.
It can also be used to modify functions inherited from
classes.
</para>
<para>
As an example, consider the following:
<literallayout class='monospaced'>
do_foo() {
bbplain first
fn
}
fn_prepend() {
bbplain second
}
fn() {
bbplain third
}
do_foo_append() {
bbplain fourth
}
</literallayout>
The output from <filename>do_foo</filename>
results in the following:
<literallayout class='monospaced'>
recipename do_foo: first
recipename do_foo: second
recipename do_foo: third
recipename do_foo: fourth
</literallayout>
<note>
Overrides and override-style operators can
be applied to any shell function, not just
<link linkend='tasks'>tasks</link>.
</note>
You can use the <filename>bitbake -e</filename>&nbsp;<replaceable>recipename</replaceable>
command to view the final assembled function
after all overrides have been applied.
</para>
</section>
<section id='bitbake-style-python-functions'>
@ -1114,19 +1173,51 @@
Also in these types of functions, the datastore ("d")
is a global variable and is always automatically
available.
</para>
<note>
Variable expressions (e.g. <filename>${X}</filename>)
are no longer expanded within Python functions.
This behavior is intentional in order to allow you
to freely set variable values to expandable expressions
without having them expanded prematurely.
If you do wish to expand a variable within a Python
function, use <filename>d.getVar("X", True)</filename>.
Or, for more complicated expressions, use
<filename>d.expand()</filename>.
</note>
</para>
<note>
Variable expressions (e.g. <filename>${X}</filename>) are no
longer expanded within Python functions.
This behavior is intentional in order to allow you to freely
set variable values to expandable expressions without having
them expanded prematurely.
If you do wish to expand a variable within a Python function,
use <filename>d.getVar("X", True)</filename>.
Or, for more complicated expressions, use
<filename>d.expand()</filename>.
</note>
<para>
Similar to shell functions, you can also apply overrides
and override-style operators to BitBake-style Python
functions.
</para>
<para>
As an example, consider the following:
<literallayout class='monospaced'>
python do_foo_prepend() {
bb.plain("first")
}
python do_foo() {
bb.plain("second")
}
python do_foo_append() {
bb.plain("third")
}
</literallayout>
The output from <filename>do_foo</filename> results
in the following:
<literallayout class='monospaced'>
recipename do_foo: first
recipename do_foo: second
recipename do_foo: third
</literallayout>
You can use the <filename>bitbake -e</filename>&nbsp;<replaceable>recipename</replaceable>
command to view the final assembled function
after all overrides have been applied.
</para>
</section>
<section id='python-functions'>