_exceptions.py: Adhere to policy on private symbols

And adjust all surrounding sources for changed symbols.

Also, added new LoadErrorReason.UNSUPPORTED_PLUGIN, required
for changes in how the project will report format version errors
for plugins at creation time

This is a part of issue #285

4 files changed, 37 insertions, 17 deletions

diff --git a/buildstream/_exceptions.py b/buildstream/_exceptions.py
index 27045bece..8ed96ec98 100644
--- a/buildstream/_exceptions.py
+++ b/buildstream/_exceptions.py
@@ -29,7 +29,13 @@ _last_task_error_domain = None
 _last_task_error_reason = None
 
 
-def _get_last_exception():
+# get_last_exception()
+#
+# Fetches the last exception from the main process
+#
+# Used by regression tests
+#
+def get_last_exception():
     global _last_exception
 
     le = _last_exception
@@ -37,8 +43,13 @@ def _get_last_exception():
     return le
 
 
-# Called from regression test fixtures
-def _get_last_task_error():
+# get_last_task_error()
+#
+# Fetches the last exception from a task
+#
+# Used by regression tests
+#
+def get_last_task_error():
     global _last_task_error_domain
     global _last_task_error_reason
 
@@ -48,8 +59,14 @@ def _get_last_task_error():
     return (d, r)
 
 
-# Called from the scheduler when an error is encountered
-def _set_last_task_error(domain, reason):
+# set_last_task_error()
+#
+# Sets the last exception of a task
+#
+# This is set by some internals to inform regression
+# tests about how things failed in a machine readable way
+#
+def set_last_task_error(domain, reason):
     global _last_task_error_domain
     global _last_task_error_reason
 
@@ -150,17 +167,20 @@ class LoadErrorReason(Enum):
     # BuildStream does not support the required project format version
     UNSUPPORTED_PROJECT = 7
 
+    # Project requires a newer version of a plugin than the one which was loaded
+    UNSUPPORTED_PLUGIN = 8
+
     # A conditional expression failed to resolve
-    EXPRESSION_FAILED = 8
+    EXPRESSION_FAILED = 9
 
     # An assertion was intentionally encoded into project YAML
-    USER_ASSERTION = 9
+    USER_ASSERTION = 10
 
     # A list composition directive did not apply to any underlying list
-    TRAILING_LIST_DIRECTIVE = 10
+    TRAILING_LIST_DIRECTIVE = 11
 
     # Conflicting junctions in subprojects
-    CONFLICTING_JUNCTION = 11
+    CONFLICTING_JUNCTION = 12
 
 
 # LoadError
diff --git a/buildstream/_scheduler/job.py b/buildstream/_scheduler/job.py
index d4f5238c5..5d2e22646 100644
--- a/buildstream/_scheduler/job.py
+++ b/buildstream/_scheduler/job.py
@@ -30,7 +30,7 @@ import multiprocessing
 from ruamel import yaml
 
 # BuildStream toplevel imports
-from .._exceptions import BstError, _set_last_task_error
+from .._exceptions import BstError, set_last_task_error
 from .._message import Message, MessageType, unconditional_messages
 from ..plugin import _plugin_lookup
 from .. import _yaml, _signals, utils
@@ -401,8 +401,8 @@ class Job():
             # For regression tests only, save the last error domain / reason
             # reported from a child task in the main process, this global state
             # is currently managed in _exceptions.py
-            _set_last_task_error(envelope.message['domain'],
-                                 envelope.message['reason'])
+            set_last_task_error(envelope.message['domain'],
+                                envelope.message['reason'])
         elif envelope.message_type == 'result':
             assert self.result is None
             self.result = envelope.message
diff --git a/buildstream/_scheduler/queue.py b/buildstream/_scheduler/queue.py
index 0cea1005f..d03ce6864 100644
--- a/buildstream/_scheduler/queue.py
+++ b/buildstream/_scheduler/queue.py
@@ -28,7 +28,7 @@ import traceback
 from .job import Job
 
 # BuildStream toplevel imports
-from .._exceptions import BstError, _set_last_task_error
+from .._exceptions import BstError, set_last_task_error
 from .._message import Message, MessageType
 
 
@@ -229,7 +229,7 @@ class Queue():
             #
             # This just allows us stronger testing capability
             #
-            _set_last_task_error(e.domain, e.reason)
+            set_last_task_error(e.domain, e.reason)
 
         except Exception as e:   # pylint: disable=broad-except
 
diff --git a/tests/testutils/runcli.py b/tests/testutils/runcli.py
index 8e3df1970..521e6487f 100644
--- a/tests/testutils/runcli.py
+++ b/tests/testutils/runcli.py
@@ -26,7 +26,7 @@ from buildstream._frontend import cli as bst_cli
 from buildstream import _yaml
 
 # Special private exception accessor, for test case purposes
-from buildstream._exceptions import BstError, _get_last_exception, _get_last_task_error
+from buildstream._exceptions import BstError, get_last_exception, get_last_task_error
 
 
 # Wrapper for the click.testing result
@@ -62,9 +62,9 @@ class Result():
             if not isinstance(exception, SystemExit):
                 self.unhandled_exception = True
 
-            self.exception = _get_last_exception()
+            self.exception = get_last_exception()
             self.task_error_domain, \
-                self.task_error_reason = _get_last_task_error()
+                self.task_error_reason = get_last_task_error()
         else:
             self.exception = None
             self.task_error_domain = None