loader: removing the NO_PROGRESS objecttristan/remove-loader-no-progress-object

While adding a mock task object to track progress in some loader
tests in commit 17144d84c2b63daf6e3aa9b42c6c773f134e8660, a new
`_NO_PROGRESS` object was added as an explicit marker to denote
that progress information should not be reported.

This complicates the code, None should be a sufficient value
for not reporting progress, while still permitting mock task
objects to capture progress if desired.

2 files changed, 12 insertions, 18 deletions

diff --git a/src/buildstream/_loader/loader.py b/src/buildstream/_loader/loader.py
index 37e00ad4b..ae729f243 100644
--- a/src/buildstream/_loader/loader.py
+++ b/src/buildstream/_loader/loader.py
@@ -37,11 +37,6 @@ from ..types import CoreWarnings, _KeyStrength
 from .._message import Message, MessageType
 
 
-# This should be used to deliberately disable progress reporting when
-# collecting an element
-_NO_PROGRESS = object()
-
-
 # Loader():
 #
 # The Loader class does the heavy lifting of parsing target
@@ -157,7 +152,7 @@ class Loader:
         self._clean_caches()
 
         # Cache how many Elements have just been loaded
-        if task is not _NO_PROGRESS:
+        if task:
             # Workaround for task potentially being None (because no State object)
             self.loaded = task.current_progress
 
@@ -232,7 +227,7 @@ class Loader:
         #
         # Any task counting *inside* the junction will be handled by
         # its loader.
-        meta_element = self._collect_element_no_deps(self._elements[filename], _NO_PROGRESS)
+        meta_element = self._collect_element_no_deps(self._elements[filename])
         if meta_element.kind != "junction":
             raise LoadError(
                 "{}{}: Expected junction but element kind is {}".format(provenance_str, filename, meta_element.kind),
@@ -598,7 +593,7 @@ class Loader:
     # Returns:
     #    (MetaElement): A partially loaded MetaElement
     #
-    def _collect_element_no_deps(self, element, task):
+    def _collect_element_no_deps(self, element, task=None):
         # Return the already built one, if we already built it
         meta_element = self._meta_elements.get(element.name)
         if meta_element:
@@ -654,7 +649,7 @@ class Loader:
 
         # Cache it now, make sure it's already there before recursing
         self._meta_elements[element.name] = meta_element
-        if task is not _NO_PROGRESS:
+        if task:
             task.add_current_progress()
 
         return meta_element
@@ -670,7 +665,7 @@ class Loader:
     # Returns:
     #    (MetaElement): A fully loaded MetaElement
     #
-    def _collect_element(self, top_element, task):
+    def _collect_element(self, top_element, task=None):
         element_queue = [top_element]
         meta_element_queue = [self._collect_element_no_deps(top_element, task)]
 
diff --git a/tests/internals/loader.py b/tests/internals/loader.py
index 6fdd9fc3a..408813a64 100644
--- a/tests/internals/loader.py
+++ b/tests/internals/loader.py
@@ -6,7 +6,6 @@ from buildstream.exceptions import LoadErrorReason
 from buildstream._exceptions import LoadError
 from buildstream._project import Project
 from buildstream._loader import MetaElement
-from buildstream._loader.loader import _NO_PROGRESS
 
 from tests.testutils import dummy_context
 
@@ -29,7 +28,7 @@ def test_one_file(datafiles):
 
     basedir = str(datafiles)
     with make_loader(basedir) as loader:
-        element = loader.load(["elements/onefile.bst"], _NO_PROGRESS)[0]
+        element = loader.load(["elements/onefile.bst"], None)[0]
 
         assert isinstance(element, MetaElement)
         assert element.kind == "pony"
@@ -40,7 +39,7 @@ def test_missing_file(datafiles):
 
     basedir = str(datafiles)
     with make_loader(basedir) as loader, pytest.raises(LoadError) as exc:
-        loader.load(["elements/missing.bst"], _NO_PROGRESS)
+        loader.load(["elements/missing.bst"], None)
 
     assert exc.value.reason == LoadErrorReason.MISSING_FILE
 
@@ -50,7 +49,7 @@ def test_invalid_reference(datafiles):
 
     basedir = str(datafiles)
     with make_loader(basedir) as loader, pytest.raises(LoadError) as exc:
-        loader.load(["elements/badreference.bst"], _NO_PROGRESS)
+        loader.load(["elements/badreference.bst"], None)
 
     assert exc.value.reason == LoadErrorReason.INVALID_YAML
 
@@ -60,7 +59,7 @@ def test_invalid_yaml(datafiles):
 
     basedir = str(datafiles)
     with make_loader(basedir) as loader, pytest.raises(LoadError) as exc:
-        loader.load(["elements/badfile.bst"], _NO_PROGRESS)
+        loader.load(["elements/badfile.bst"], None)
 
     assert exc.value.reason == LoadErrorReason.INVALID_YAML
 
@@ -72,7 +71,7 @@ def test_fail_fullpath_target(datafiles):
     fullpath = os.path.join(basedir, "elements", "onefile.bst")
 
     with make_loader(basedir) as loader, pytest.raises(LoadError) as exc:
-        loader.load([fullpath], _NO_PROGRESS)
+        loader.load([fullpath], None)
 
     assert exc.value.reason == LoadErrorReason.INVALID_DATA
 
@@ -82,7 +81,7 @@ def test_invalid_key(datafiles):
 
     basedir = str(datafiles)
     with make_loader(basedir) as loader, pytest.raises(LoadError) as exc:
-        loader.load(["elements/invalidkey.bst"], _NO_PROGRESS)
+        loader.load(["elements/invalidkey.bst"], None)
 
     assert exc.value.reason == LoadErrorReason.INVALID_DATA
 
@@ -92,6 +91,6 @@ def test_invalid_directory_load(datafiles):
 
     basedir = str(datafiles)
     with make_loader(basedir) as loader, pytest.raises(LoadError) as exc:
-        loader.load(["elements/"], _NO_PROGRESS)
+        loader.load(["elements/"], None)
 
     assert exc.value.reason == LoadErrorReason.LOADING_DIRECTORY