lib/oeqa: allow multiple layers to provide their own TEST_TARGET class

Use a python module "folder" rather than a single module within
layers to ensure multiple layers can define a TEST_TARGET class.
Current implementation using controllers.py module will only allow
a single layer to define test targets.

Add a controllers folder as well as a TestTargetLoader class whose
job is to load the given TEST_TARGET class from any number of
python modules within the oeqa/controllers/ directory of any
layer.
The only condition will be that layers will need to ensure
the TEST_TARGET class name they provide is unique otherwise there
is no guarantee which class is instantiated. a bb.warn is used
to alude to this if it happens.

(From OE-Core rev: 3f25705f4a986e06cbd397aaea52b841c1a1e054)

Signed-off-by: Sipke Vriend <sipke.vriend@xilinx.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/controllers/testtargetloader.py

@@ -0,0 +1,69 @@
+import types
+import bb
+
+# This class is responsible for loading a test target controller
+class TestTargetLoader:
+
+    # Search oeqa.controllers module directory for and return a controller  
+    # corresponding to the given target name. 
+    # AttributeError raised if not found.
+    # ImportError raised if a provided module can not be imported.
+    def get_controller_module(self, target, bbpath):
+        controllerslist = self.get_controller_modulenames(bbpath)
+        bb.note("Available controller modules: %s" % str(controllerslist))
+        controller = self.load_controller_from_name(target, controllerslist)
+        return controller
+
+    # Return a list of all python modules in lib/oeqa/controllers for each
+    # layer in bbpath
+    def get_controller_modulenames(self, bbpath):
+
+        controllerslist = []
+
+        def add_controller_list(path):
+            if not os.path.exists(os.path.join(path, '__init__.py')):
+                bb.fatal('Controllers directory %s exists but is missing __init__.py' % path)
+            files = sorted([f for f in os.listdir(path) if f.endswith('.py') and not f.startswith('_')])
+            for f in files:
+                module = 'oeqa.controllers.' + f[:-3]
+                if module not in controllerslist:
+                    controllerslist.append(module)
+                else:
+                    bb.warn("Duplicate controller module found for %s, only one added. Layers should create unique controller module names" % module)
+
+        for p in bbpath:
+            controllerpath = os.path.join(p, 'lib', 'oeqa', 'controllers')
+            bb.debug(2, 'Searching for target controllers in %s' % controllerpath)
+            if os.path.exists(controllerpath):
+                add_controller_list(controllerpath)
+        return controllerslist
+
+    # Search for and return a controller from given target name and
+    # set of module names. 
+    # Raise AttributeError if not found.
+    # Raise ImportError if a provided module can not be imported
+    def load_controller_from_name(self, target, modulenames):
+        for name in modulenames:
+            obj = self.load_controller_from_module(target, name)
+            if obj:
+                return obj
+        raise AttributeError("Unable to load {0} from available modules: {1}".format(target, str(modulenames)))
+
+    # Search for and return a controller or None from given module name
+    def load_controller_from_module(self, target, modulename):
+        obj = None
+        # import module, allowing it to raise import exception
+        module = __import__(modulename, globals(), locals(), [target])
+        # look for target class in the module, catching any exceptions as it
+        # is valid that a module may not have the target class.
+        try:
+            obj = getattr(module, target)
+            if obj: 
+                from oeqa.targetcontrol import BaseTarget
+                if (not isinstance(obj, (type, types.ClassType))):
+                    bb.warn("Target {0} found, but not of type Class".format(target))
+                if( not issubclass(obj, BaseTarget)):
+                    bb.warn("Target {0} found, but subclass is not BaseTarget".format(target))
+        except:
+            obj = None
+        return obj