plugin.py/pluginfactory.py: Implementing BST_MIN_VERSION

The BST_MIN_VERSION guards assert that the BuildStream core which
loaded the plugin is compatible with the plugin itself.

This commit adds BST_MIN_VERSION to the base plugin.py with documentation
informing Plugin authors how to set the minimum version, and also adds
the assertions at plugin loading time in pluginfactory.py.

This commit also:

  * Adds the BST_MIN_VERSION specification to all current core plugins
  * Adds the BST_MIN_VERSION specification to plugins used in test cases

19 files changed, 51 insertions, 0 deletions

diff --git a/tests/elements/filter/basic/element_plugins/dynamic.py b/tests/elements/filter/basic/element_plugins/dynamic.py
index bf079111f..db92a6647 100644
--- a/tests/elements/filter/basic/element_plugins/dynamic.py
+++ b/tests/elements/filter/basic/element_plugins/dynamic.py
@@ -3,6 +3,9 @@ from buildstream import Element, Scope
 
 # Copies files from the dependent element but inserts split-rules using dynamic data
 class DynamicElement(Element):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         node.validate_keys(["split-rules"])
         self.split_rules = {key: value.as_str_list() for key, value in node.get_mapping("split-rules").items()}
diff --git a/tests/format/project/plugin-allowed/plugins/foo.py b/tests/format/project/plugin-allowed/plugins/foo.py
index bf884233c..76d9bfd3c 100644
--- a/tests/format/project/plugin-allowed/plugins/foo.py
+++ b/tests/format/project/plugin-allowed/plugins/foo.py
@@ -2,6 +2,9 @@ from buildstream import Element
 
 
 class FooElement(Element):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, config):
         pass
 
diff --git a/tests/format/project/plugin-forbidden/forbidden-plugins/forbidden-plugin.py b/tests/format/project/plugin-forbidden/forbidden-plugins/forbidden-plugin.py
index bf884233c..76d9bfd3c 100644
--- a/tests/format/project/plugin-forbidden/forbidden-plugins/forbidden-plugin.py
+++ b/tests/format/project/plugin-forbidden/forbidden-plugins/forbidden-plugin.py
@@ -2,6 +2,9 @@ from buildstream import Element
 
 
 class FooElement(Element):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, config):
         pass
 
diff --git a/tests/format/project/plugin-no-load-ref/plugins/noloadref.py b/tests/format/project/plugin-no-load-ref/plugins/noloadref.py
index e2fe0ac46..2b8fd0b51 100644
--- a/tests/format/project/plugin-no-load-ref/plugins/noloadref.py
+++ b/tests/format/project/plugin-no-load-ref/plugins/noloadref.py
@@ -6,6 +6,9 @@ from buildstream import Source
 # Use this to test that the core behaves as expected with such plugins.
 #
 class NoLoadRefSource(Source):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         pass
 
diff --git a/tests/format/project/plugin-preflight-error/errorplugin/preflighterror.py b/tests/format/project/plugin-preflight-error/errorplugin/preflighterror.py
index db2895f8b..a03cb64ee 100644
--- a/tests/format/project/plugin-preflight-error/errorplugin/preflighterror.py
+++ b/tests/format/project/plugin-preflight-error/errorplugin/preflighterror.py
@@ -2,6 +2,9 @@ from buildstream import Source, SourceError
 
 
 class PreflightErrorSource(Source):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         pass
 
diff --git a/tests/frontend/configuredwarning/plugins/corewarn.py b/tests/frontend/configuredwarning/plugins/corewarn.py
index bef0a4904..bcd40753c 100644
--- a/tests/frontend/configuredwarning/plugins/corewarn.py
+++ b/tests/frontend/configuredwarning/plugins/corewarn.py
@@ -3,6 +3,9 @@ from buildstream.plugin import CoreWarnings
 
 
 class CoreWarn(Element):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         pass
 
diff --git a/tests/frontend/configuredwarning/plugins/warninga.py b/tests/frontend/configuredwarning/plugins/warninga.py
index 9fd8dc61b..4ad0f3d20 100644
--- a/tests/frontend/configuredwarning/plugins/warninga.py
+++ b/tests/frontend/configuredwarning/plugins/warninga.py
@@ -4,6 +4,9 @@ WARNING_A = "warning-a"
 
 
 class WarningA(Element):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         pass
 
diff --git a/tests/frontend/configuredwarning/plugins/warningb.py b/tests/frontend/configuredwarning/plugins/warningb.py
index 64d25ef39..c7a995cf8 100644
--- a/tests/frontend/configuredwarning/plugins/warningb.py
+++ b/tests/frontend/configuredwarning/plugins/warningb.py
@@ -4,6 +4,9 @@ WARNING_B = "warning-b"
 
 
 class WarningB(Element):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         pass
 
diff --git a/tests/frontend/consistencyerror/plugins/consistencybug.py b/tests/frontend/consistencyerror/plugins/consistencybug.py
index abcbbc997..1952894ca 100644
--- a/tests/frontend/consistencyerror/plugins/consistencybug.py
+++ b/tests/frontend/consistencyerror/plugins/consistencybug.py
@@ -2,6 +2,9 @@ from buildstream import Source
 
 
 class ConsistencyBugSource(Source):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         pass
 
diff --git a/tests/frontend/consistencyerror/plugins/consistencyerror.py b/tests/frontend/consistencyerror/plugins/consistencyerror.py
index 2e30d4842..34af45782 100644
--- a/tests/frontend/consistencyerror/plugins/consistencyerror.py
+++ b/tests/frontend/consistencyerror/plugins/consistencyerror.py
@@ -2,6 +2,9 @@ from buildstream import Source, SourceError
 
 
 class ConsistencyErrorSource(Source):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         pass
 
diff --git a/tests/frontend/project/plugins/randomelement.py b/tests/frontend/project/plugins/randomelement.py
index e9be98fc7..12afaaa6d 100644
--- a/tests/frontend/project/plugins/randomelement.py
+++ b/tests/frontend/project/plugins/randomelement.py
@@ -4,6 +4,9 @@ from buildstream import Element
 
 
 class RandomElement(Element):
+
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         pass
 
diff --git a/tests/frontend/project/sources/fetch_source.py b/tests/frontend/project/sources/fetch_source.py
index c62d1d29a..6078e5e5f 100644
--- a/tests/frontend/project/sources/fetch_source.py
+++ b/tests/frontend/project/sources/fetch_source.py
@@ -32,6 +32,9 @@ class FetchFetcher(SourceFetcher):
 
 
 class FetchSource(Source):
+
+    BST_MIN_VERSION = "2.0"
+
     # Read config to know which URLs to fetch
     def configure(self, node):
         self.original_urls = node.get_str_list("urls")
diff --git a/tests/internals/pluginloading/customelement/pluginelements/foo.py b/tests/internals/pluginloading/customelement/pluginelements/foo.py
index c6a85a5b1..bdb6c8982 100644
--- a/tests/internals/pluginloading/customelement/pluginelements/foo.py
+++ b/tests/internals/pluginloading/customelement/pluginelements/foo.py
@@ -2,6 +2,9 @@ from buildstream import Element
 
 
 class FooElement(Element):
+
+    BST_MIN_VERSION = "2.0"
+
     def preflight(self):
         pass
 
diff --git a/tests/internals/pluginloading/customsource/pluginsources/foo.py b/tests/internals/pluginloading/customsource/pluginsources/foo.py
index fce5239b1..c5229f3e2 100644
--- a/tests/internals/pluginloading/customsource/pluginsources/foo.py
+++ b/tests/internals/pluginloading/customsource/pluginsources/foo.py
@@ -2,6 +2,9 @@ from buildstream import Source
 
 
 class FooSource(Source):
+
+    BST_MIN_VERSION = "2.0"
+
     def preflight(self):
         pass
 
diff --git a/tests/plugins/deprecationwarnings/plugins/elements/deprecated_plugin.py b/tests/plugins/deprecationwarnings/plugins/elements/deprecated_plugin.py
index 1badf59af..244009764 100644
--- a/tests/plugins/deprecationwarnings/plugins/elements/deprecated_plugin.py
+++ b/tests/plugins/deprecationwarnings/plugins/elements/deprecated_plugin.py
@@ -2,6 +2,7 @@ from buildstream import BuildElement
 
 
 class DeprecatedPlugin(BuildElement):
+    BST_MIN_VERSION = "2.0"
     BST_PLUGIN_DEPRECATED = True
     BST_PLUGIN_DEPRECATION_MESSAGE = "Here is some detail."
 
diff --git a/tests/sourcecache/project/plugins/elements/always_fail.py b/tests/sourcecache/project/plugins/elements/always_fail.py
index 43dba5626..bc3ed57b6 100644
--- a/tests/sourcecache/project/plugins/elements/always_fail.py
+++ b/tests/sourcecache/project/plugins/elements/always_fail.py
@@ -23,6 +23,9 @@ from buildstream.buildelement import BuildElement
 
 
 class AlwaysFail(BuildElement):
+
+    BST_MIN_VERSION = "2.0"
+
     def assemble(self, sandbox):
         raise ElementError("Always fails")
 
diff --git a/tests/sources/no-fetch-cached/plugins/sources/always_cached.py b/tests/sources/no-fetch-cached/plugins/sources/always_cached.py
index aef13279b..b5dfd772c 100644
--- a/tests/sources/no-fetch-cached/plugins/sources/always_cached.py
+++ b/tests/sources/no-fetch-cached/plugins/sources/always_cached.py
@@ -11,6 +11,8 @@ from buildstream import Source
 
 
 class AlwaysCachedSource(Source):
+    BST_MIN_VERSION = "2.0"
+
     def configure(self, node):
         pass
 
diff --git a/tests/sources/previous_source_access/plugins/sources/foo_transform.py b/tests/sources/previous_source_access/plugins/sources/foo_transform.py
index dbc44c8aa..15fef43f8 100644
--- a/tests/sources/previous_source_access/plugins/sources/foo_transform.py
+++ b/tests/sources/previous_source_access/plugins/sources/foo_transform.py
@@ -14,6 +14,7 @@ from buildstream import Source, SourceError, utils
 
 
 class FooTransformSource(Source):
+    BST_MIN_VERSION = "2.0"
 
     # We need access to previous both at track time and fetch time
     BST_REQUIRES_PREVIOUS_SOURCES_TRACK = True
diff --git a/tests/sources/project_key_test/plugins/sources/key-test.py b/tests/sources/project_key_test/plugins/sources/key-test.py
index 88a211738..046034804 100644
--- a/tests/sources/project_key_test/plugins/sources/key-test.py
+++ b/tests/sources/project_key_test/plugins/sources/key-test.py
@@ -7,6 +7,8 @@ class KeyTest(Source):
     """ This plugin should fail if get_unique_key is called before track
     """
 
+    BST_MIN_VERSION = "2.0"
+
     def preflight(self):
         pass