Let users override project artifacts options

A project can specify its artifacts cache sharing settings, and users can
define a default artifacts cache to use as a fallback.

With this change, users can also override the project configuration with
their own.

That means for a project named "libfoo", BuildStream will resolve the
artifacts-related options in the following order:

1. the projects.libfoo.artifacts options from the user configuration;
2. if the above was not defined, then the artifacts options from the
   project configuration;
3. if the above was not defined, then the artifacts options from the
   user configuration;

Fixes #87

4 files changed, 35 insertions, 3 deletions

diff --git a/buildstream/_artifactcache/artifactcache.py b/buildstream/_artifactcache/artifactcache.py
index 41625b655..2b779c95f 100644
--- a/buildstream/_artifactcache/artifactcache.py
+++ b/buildstream/_artifactcache/artifactcache.py
@@ -67,7 +67,14 @@ class ArtifactCache():
         self.__pull_local = False
         self.__push_local = False
 
-        if any((project.artifact_pull, project.artifact_push)):
+        project_overrides = context.project_overrides.get(project.name, {}).get('artifacts', {})
+
+        if any((project_overrides.get('pull-url'), project_overrides.get('push-url'))):
+            self.artifact_pull = project_overrides.get('pull-url', '')
+            self.artifact_push = project_overrides.get('push-url', '')
+            self.artifact_push_port = project_overrides.get('push-port', 22)
+
+        elif any((project.artifact_pull, project.artifact_push)):
             self.artifact_pull = project.artifact_pull
             self.artifact_push = project.artifact_push
             self.artifact_push_port = project.artifact_push_port
diff --git a/buildstream/_pipeline.py b/buildstream/_pipeline.py
index 07f72bdc9..ba85c1147 100644
--- a/buildstream/_pipeline.py
+++ b/buildstream/_pipeline.py
@@ -133,7 +133,6 @@ class Pipeline():
                  cache_ticker=None):
         self.context = context
         self.project = project
-        self.artifacts = ArtifactCache(self.context, self.project)
         self.session_elements = 0
         self.total_elements = 0
         self.unused_workspaces = []
@@ -148,6 +147,8 @@ class Pipeline():
         # Resolve project variant now that we've decided on one
         project._resolve(loader.project_variant)
 
+        self.artifacts = ArtifactCache(self.context, self.project)
+
         # Create the factories after resolving the project
         pluginbase = PluginBase(package='buildstream.plugins')
         self.element_factory = ElementFactory(pluginbase, project._plugin_element_paths)
diff --git a/buildstream/context.py b/buildstream/context.py
index 17503150f..6f378f700 100644
--- a/buildstream/context.py
+++ b/buildstream/context.py
@@ -118,6 +118,9 @@ class Context():
         self.sched_error_action = 'continue'
         """What to do when a build fails in non interactive mode"""
 
+        self.project_overrides = {}
+        """Per-project overrides of project configurations"""
+
         # Make sure the XDG vars are set in the environment before loading anything
         self._init_xdg()
 
@@ -163,7 +166,8 @@ class Context():
             'strict', 'sourcedir',
             'builddir', 'artifactdir',
             'logdir', 'scheduler',
-            'artifacts', 'logging'
+            'artifacts', 'logging',
+            'projects',
         ])
 
         self.strict_build_plan = _yaml.node_get(defaults, bool, 'strict')
@@ -210,6 +214,9 @@ class Context():
         self.sched_pushers = _yaml.node_get(scheduler, int, 'pushers')
         self.sched_network_retries = _yaml.node_get(scheduler, int, 'network-retries')
 
+        # Load per-projects overrides
+        self.project_overrides = _yaml.node_get(defaults, Mapping, 'projects', default_value={})
+
         profile_end(Topics.LOAD_CONTEXT, 'load')
 
         valid_actions = ['continue', 'quit']
diff --git a/buildstream/data/userconfig.yaml b/buildstream/data/userconfig.yaml
index 1cce9fcd5..ce0812840 100644
--- a/buildstream/data/userconfig.yaml
+++ b/buildstream/data/userconfig.yaml
@@ -96,3 +96,20 @@ logging:
   element-format: |
 
     %{state: >12} %{key} %{name} %{variant} %{workspace-dirs}
+
+#
+#    Per project overrides
+#
+# Some settings defined in the project configuration can be overridden by
+# the user configuration.
+#
+# projects:
+#
+#   project1:
+#     artifacts:
+#       pull-url: https://artifacts.com
+#       push-url: artifacts@artifacts.com:artifacts
+#       push-port: 443
+#
+#   project2:
+#     ...