Tools/ardupilotwaf: improve dronecangen dependency tracking

Have the build depend on the input message definition files and the
generator source code so that the code is regenerated if either change.

Tools/ardupilotwaf/dronecangen.py

@@ -20,10 +20,10 @@ def run(self):
         python = self.env.get_flat('PYTHON')
         out = self.env.get_flat('OUTPUT_DIR')
         src = self.env.get_flat('SRC')
-        dsdlc = self.env.get_flat("DC_DSDL_COMPILER")
+        dsdlc = self.env.get_flat("DC_DSDL_COMPILER_DIR")
 
         cmd = ['{}'.format(python),
-               '{}'.format(dsdlc),
+               '{}/dronecan_dsdlc.py'.format(dsdlc),
                '-O{}'.format(out)] + [x.abspath() for x in self.inputs]
         ret = self.exec_command(cmd)
         if ret != 0:
@@ -55,6 +55,16 @@ def process_dronecangen(self):
         self.bld.fatal('dronecangen: missing option output_dir')
 
     inputs = self.to_nodes(self.source)
+    # depend on each message file in the source so rebuilds will occur properly
+    deps = []
+    for inp in inputs:
+        deps.extend(inp.ant_glob("**/*.uavcan"))
+    # also depend on the generator source itself
+    dsdlc_dir = self.env.get_flat("DC_DSDL_COMPILER_DIR")
+    dsdlc = self.bld.root.find_node(dsdlc_dir) # expected to be absolute
+    if dsdlc is None:
+        self.bld.fatal("dronecangen: waf couldn't find dsdlc at abspath {}".format(dsdlc_dir))
+    deps.extend(dsdlc.ant_glob("**/*.py **/*.em"))
     outputs = []
 
     self.source = []
@@ -63,6 +73,7 @@ def process_dronecangen(self):
         self.output_dir = self.bld.bldnode.find_or_declare(self.output_dir)
 
     task = self.create_task('dronecangen', inputs, outputs)
+    task.dep_nodes = deps
     task.env['OUTPUT_DIR'] = self.output_dir.abspath()
 
     task.env.env = dict(os.environ)
@@ -73,5 +84,4 @@ def configure(cfg):
     """
     env = cfg.env
     env.DC_DSDL_COMPILER_DIR = cfg.srcnode.make_node('modules/DroneCAN/dronecan_dsdlc/').abspath()
-    env.DC_DSDL_COMPILER = env.DC_DSDL_COMPILER_DIR + '/dronecan_dsdlc.py'
-    cfg.msg('DC_DSDL compiler', env.DC_DSDL_COMPILER)
+    cfg.msg('DC_DSDL compiler in', env.DC_DSDL_COMPILER_DIR)