bitbake: build: implement custom progress handlers injected via OE_EXTRA_IMPORTS

A separate patch to base.bbclass (in poky) will add the OE_EXTRA_IMPORTS
variable. The contents are appended into OE_IMPORTS. This provides a
mechanism by which layers (in their layer.conf) can make custom progress
handlers available.

As a backup, individual recipes can inject progress handlers into
__builtins__.

Custom handlers are expected to have this __init__ signature:

    def __init__(self, d, outfile=None, otherargs=None):

Recipes can then use the handlers like this:

    do_task[progress] = "custom:mylayer.util.ProgressHandler[:args]"

The last part (everything after and including the second colon) is
optional. If provided, it is passed to HandlerClass's __init__ as
otherargs="args". Otherwise, otherargs=None.

(Bitbake rev: 20289d62c84c393990dd3deb0cca1b17c09092e6)

Signed-off-by: Chris Laplante <chris.laplante@agilent.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/build.py

@@ -356,6 +356,27 @@ def create_progress_handler(func, progress, logfile, d):
     elif progress.startswith('outof:'):
         # Use specified regex
         return bb.progress.OutOfProgressHandler(d, regex=progress.split(':', 1)[1], outfile=logfile)
+    elif progress.startswith("custom:"):
+        # Use a custom progress handler that was injected via OE_EXTRA_IMPORTS or __builtins__
+        import functools
+        from types import ModuleType
+
+        parts = progress.split(":", 2)
+        _, cls, otherargs = parts[0], parts[1], (parts[2] or None) if parts[2:] else None
+        if cls:
+            def resolve(x, y):
+                if not x:
+                    return None
+                if isinstance(x, ModuleType):
+                    return getattr(x, y, None)
+                return x.get(y)
+            cls_obj = functools.reduce(resolve, cls.split("."), bb.utils._context)
+            if not cls_obj:
+                # Fall-back on __builtins__
+                cls_obj = functools.reduce(lambda x, y: x.get(y), cls.split("."), __builtins__)
+            if cls_obj:
+                return cls_obj(d, outfile=logfile, otherargs=otherargs)
+            bb.warn('%s: unknown custom progress handler in task progress varflag value "%s", ignoring' % (func, cls))
     else:
         bb.warn('%s: invalid task progress varflag value "%s", ignoring' % (func, progress))