[OE-core] [PATCH] recipe_links.bbclass: introduction

[Mark Asselstine]

This is a new class which can be used (for example via USER_CLASSES in
local.conf) to make your build more development friendly. When
included this class will create symlinks to the various bb and
bbappend files in WORKDIR.

Normally when you are debugging or extending a package's recipe files
a developer will employ one of a few indirect techniques to determine
where bb and bbappends files associated with a recipe exist. For
example they might use bitbake-layers show-recipes or similar, or
simply rely on their experience to guide them. Even after working with
openembedded for serveral years now I find these techniques tedious
and time consuming, and sometimes even hit and miss.

Since the whereabouts of these files are already stored in various
files at parse time we can create symlinks to simplify the task of
finding these files, making them available in WORKDIR for easy
inpsection and in a convenient location if using devshel for instance.

For now this work is completely optional but we could conceivable make
this the default behavior if folks find it is convenient and the cost
of performing these operations across all builds is minimal enough.

recipe_links can safely be added to USER_CLASSES for existing builds,
care has been taken to avoid this action causing anything to be
rebuilt. After this has been added you can either 'bitbake <recipe> -C
unpack' or 'bitbake <recipe> -c create_recipe_links' to cause the
links to be created in the WORKDIR for the specified recipe.

Signed-off-by: Mark Asselstine <mark.asselstine at windriver.com>
---
 meta/classes/recipe_links.bbclass | 79 +++++++++++++++++++++++++++++++++++++++
 meta/conf/documentation.conf      |  1 +
 2 files changed, 80 insertions(+)
 create mode 100644 meta/classes/recipe_links.bbclass

diff --git a/meta/classes/recipe_links.bbclass b/meta/classes/recipe_links.bbclass
new file mode 100644
index 0000000..ea97605
--- /dev/null
+++ b/meta/classes/recipe_links.bbclass
@@ -0,0 +1,79 @@
+# Create symlink in WORKDIR to the various bb and
+# bbappend files used to define the package ops
+
+# Create a symlink given src and dst paths
+def create_link(d, src, dst):
+    if os.path.islink(dst):
+        try:
+            os.unlink(dst)
+        except OSError as err:
+            bb.error("  Failed to cleanup old link %s: %s"
+                         % (os.path.basename(dst), os.strerror(err.errno)))
+            return False
+
+
+    try:
+        os.symlink(src, dst)
+    except OSError as err:
+        bb.error("  Failed to create file link for %s: %s"
+                     % (src, os.strerror(err.errno)))
+        return False
+
+    return True
+
+# Ensure the work is scheduled. We do this as a func
+# to avoid sig changes causing things to be rebuilt
+# when the class is added/removed after the fact.
+do_unpack[postfuncs] += "create_recipe_links "
+do_unpack[vardepsexclude] += "create_recipe_links "
+python create_recipe_links() {
+    import re
+    import glob
+
+    workdir = d.getVar('WORKDIR')
+
+    # Main recipe file
+    bb.note("Add main recipe file link:")
+    bb_path = d.getVar('FILE')
+    bb_filename = os.path.basename(bb_path)
+    bb_destname = "%s/%s" % (workdir, bb_filename)
+    bb.note("  Linking %s" % bb_path)
+    if not create_link(d, bb_path, bb_destname):
+        return False
+
+    # Cleanup old bbappends links
+    bb.note("Removing old bbappend links:")
+    pn = d.getVar('PN')
+    files = glob.glob('%s/[0-9][0-9]_%s.bbappend' % (workdir,pn))
+    files += glob.glob('%s/[0-9][0-9]_%s_*.bbappend' % (workdir, pn))
+    for filename in files:
+        bb.note("  Removing: %s" % filename)
+        try:
+            os.unlink(filename)
+        except OSError as err:
+            bb.error("  Failed to cleanup old link %s: %s" %
+                         (os.path.basename(filename), os.strerror(err.errno)))
+            return False
+
+    # Add bbappends links
+    bb.note("Adding bbappend links:")
+    included_files = d.getVar('BBINCLUDED').split()
+    bbappend_re = re.compile( r".*/%s(_[^/]*)?\.bbappend$" % re.escape(pn))
+    for filename in included_files:
+        if bbappend_re.match(filename):
+            bb.note("  Linking %s" % filename)
+            destname = "00_%s" % (os.path.basename(filename))
+            while os.path.exists("%s/%s" % (workdir, destname)):
+                 destname = str(int(destname[:2]) + 1).zfill(2) + destname[2:]
+            if not create_link(d, filename, "%s/%s" % (workdir, destname)):
+                return False
+
+    return True
+}
+
+# In addition to the func we want to make things able to be (re)run
+# easily by the user so ensure it is available as a task.
+addtask do_create_recipe_links
+python do_create_recipe_links() {
+    bb.build.exec_func("create_recipe_links", d)
+}
diff --git a/meta/conf/documentation.conf b/meta/conf/documentation.conf
index 254f8f1..2f6e686 100644
--- a/meta/conf/documentation.conf
+++ b/meta/conf/documentation.conf
@@ -21,6 +21,7 @@ do_devpyshell[doc] = "Starts an interactive Python shell for development/debuggi
 do_devshell[doc] = "Starts a shell with the environment set up for development/debugging"
 do_diffconfig[doc] = "Compares the old and new config files after running do_menuconfig for the kernel"
 do_fetch[doc] = "Fetches the source code"
+do_create_recipe_links[doc] = "Creates links to bb and bbappend files in a package's WORKDIR"
 do_install[doc] = "Copies files from the compilation directory to a holding area"
 do_install_ptest_base[doc] = "Copies the runtime test suite files from the compilation directory to a holding area"
 do_kernel_checkout[doc] = "Checks out source/meta branches for a linux-yocto style kernel"
-- 
2.7.4