init

core/dbt/events/events.py

@@ -0,0 +1,46 @@
+
+from typing import NamedTuple, NoReturn, Union
+
+
+# common trick for getting mypy to do exhaustiveness checks
+# will come up with something like `"assert_never" has incompatible type`
+# if something is missing.
+def assert_never(x: NoReturn) -> NoReturn:
+    raise AssertionError("Unhandled type: {}".format(type(x).__name__))
+
+# The following classes represent the data necessary to describe a
+# particular event to both human readable logs, and machine reliable
+# event streams. The transformation to these forms will live in outside
+# functions.
+#
+# Until we drop support for Python 3.6 we must use NamedTuples over
+# frozen dataclasses.
+
+# TODO dummy class
+class OK(NamedTuple):
+    result: int
+
+
+# TODO dummy class
+class Failure(NamedTuple):
+    msg: str
+
+
+# using a union instead of inheritance means that this set cannot
+# be extended outside this file, and thus mypy can do exhaustiveness
+# checks for us.
+Event = Union[OK, Failure]
+
+
+# function that translates any instance of the above event types
+# into its human-readable message.
+#
+# This could instead be implemented as a method on an ABC for all
+# above classes, but this at least puts all that logic in one place.
+def humanMsg(r: Event) -> str:
+    if isinstance(r, OK):
+        return str(r.result)
+    elif isinstance(r, Failure):
+        return "Failure: " + r.msg
+    else:
+        assert_never(r)

core/dbt/task/parse.py

@@ -81,6 +81,7 @@ def compile_manifest(self):
         self.graph = compiler.compile(self.manifest)
 
     def run(self):
+        events.register(Progress(ParseStart))
         print_timestamped_line('Start parsing.')
         self.get_full_manifest()
         if self.args.compile: