RE: [OE-core] [PATCH] externalsrc.bbclass: Allow externalsrc to be extended with extra classes

[Peter Kjellerstedt <peter.kjellerstedt@axis.com>]

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I thought of another problem with the wrapper class solution: if we need to actually backport a newer version of the class from, e.g., Poky master, then there is now no natural place for it since it is occupied by the wrapper class. That means we would either have to rename the backported class, or put it somewhere else than in “classes”. It also means backporting a class requires the wrapper class to be modified.

Here is a question for Richard: what do you think of an idea I had to add support in bitbake for extending classes? I do not mean to add something like bbclassappend, as I know that is troublesome. My idea instead is something like the prefuncs/postfuncs that we have for functions. I.e., before actually doing the inherit of a class foo, bitbake would inherit anything specified in BBCLASS_PRE_INHERIT:foo, and after inheriting the class it would automatically inherit anything in BBCLASS_POST_INHERIT:foo.  That way one can simply extend a class through normal variable operations, making it easy to do, e.g., in the distro configuration.

//Peter

From: openembedded-core@lists.openembedded.org <openembedded-core@lists.openembedded.org> On Behalf Of Peter Kjellerstedt
Sent: den 20 oktober 2021 03:32
To: Jose Quaresma <quaresma.jose@gmail.com>
Cc: OE-core <openembedded-core@lists.openembedded.org>
Subject: Re: [OE-core] [PATCH] externalsrc.bbclass: Allow externalsrc to be extended with extra classes

Well, I had not considered that option. I can’t say I am to keen on having wrapper classes with the same name as the upstream classes as I think it leads to confusion. And the solution doesn’t scale very well (what if two layers want to override the same class?). But on the positive side it works for any class without requiring changes to OE-Core. And I guess the latter wins. I wish there was a more bitbakey way to add to classes though (bbclassappend anyone? 😉).

//Peter

From: Jose Quaresma <quaresma.jose@gmail.com<mailto:quaresma.jose@gmail.com>>
Sent: den 19 oktober 2021 19:15
To: Peter Kjellerstedt <peter.kjellerstedt@axis.com<mailto:peter.kjellerstedt@axis.com>>
Cc: OE-core <openembedded-core@lists.openembedded.org<mailto:openembedded-core@lists.openembedded.org>>
Subject: Re: [OE-core] [PATCH] externalsrc.bbclass: Allow externalsrc to be extended with extra classes

Hi Peter,

require the class on the new one will do the same
and we don't need any changes for that
but I may not be seeing everything

require ${COREBASE}/meta/classes/externalsrc.bbclass

Jose

Peter Kjellerstedt <peter.kjellerstedt@axis.com<mailto:peter.kjellerstedt@axis.com>> escreveu no dia terça, 19/10/2021 à(s) 18:03:
The EXTERNALSRC_EXTENSIONS variable holds a list of additional classes
that will be inherited when externalsrc is inherited.

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com<mailto:peter.kjellerstedt@axis.com>>
---

We have had a local copy of this class for a long time since we need
to make it suppport a local class when checking BBCLASSEXTEND. And
now we wanted to add some more functionality that should be active
when externalsrc is in use. So instead of forking the class even
more, I thought it would be better to make the upstream class
extendable. The solution was inspired by USERADDEXTENSION in
useradd.bbclass.

 meta/classes/externalsrc.bbclass | 5 +++++
 meta/conf/documentation.conf     | 1 +
 2 files changed, 6 insertions(+)

diff --git a/meta/classes/externalsrc.bbclass b/meta/classes/externalsrc.bbclass
index abfe24bace..488d75760f 100644
--- a/meta/classes/externalsrc.bbclass
+++ b/meta/classes/externalsrc.bbclass
@@ -265,3 +265,8 @@ def srctree_configure_hash_files(d):
     return ' '.join(out_items)

 EXPORT_FUNCTIONS do_buildclean
+
+# Use the following to extend externalsrc with custom functionality
+EXTERNALSRC_EXTENSIONS ??= ""
+
+inherit ${EXTERNALSRC_EXTENSIONS}
diff --git a/meta/conf/documentation.conf b/meta/conf/documentation.conf
index 80ad8e10d5..6d5b734b02 100644
--- a/meta/conf/documentation.conf
+++ b/meta/conf/documentation.conf
@@ -160,6 +160,7 @@ EXTENDPE[doc] = "Used with file and pathnames to create a prefix for a recipe's
 EXTENDPKGV[doc] = "The full package version specification as it appears on the final packages produced by a recipe."
 EXTERNALSRC[doc] = "If externalsrc.bbclass is inherited, this variable points to the source tree, which is outside of the OpenEmbedded build system."
 EXTERNALSRC_BUILD[doc] = "If externalsrc.bbclass is inherited, this variable points to the directory in which the recipe's source code is built, which is outside of the OpenEmbedded build system."
+EXTERNALSRC_EXTENSIONS[doc] = "A list of additional classes that will be inherited when externalsrc is inherited."
 EXTRA_IMAGE_FEATURES[doc] = "The list of additional features to include in an image. Configure this variable in the conf/local.conf file in the Build Directory."
 EXTRA_IMAGEDEPENDS[doc] = "A list of recipes to build that do not provide packages for installing into the root filesystem. Use this variable to list recipes that are required to build the final image, but not needed in the root filesystem."
 EXTRA_OECMAKE[doc] = "Additional cmake options."


--
Best regards,

José Quaresma

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