Merge branch 'tristan/version-specific-config' into 'master'

Support version specific configuration files

See merge request BuildStream/buildstream!1941

3 files changed, 50 insertions, 3 deletions

diff --git a/doc/source/using_config.rst b/doc/source/using_config.rst
index 302abb2f1..ba38173e3 100644
--- a/doc/source/using_config.rst
+++ b/doc/source/using_config.rst
@@ -22,6 +22,17 @@ invoking ``bst``, an attempt is made to load user specific configuration from
 ``$XDG_CONFIG_HOME/buildstream.conf``. On most Linux based systems, the location
 will be ``~/.config/buildstream.conf``
 
+.. note::
+
+   If you have have multiple major versions of BuildStream installed, you
+   can have separate configuration files in your ``${XDG_CONFIG_HOME}``.
+
+   You can do this by naming them according to the major versions of
+   BuildStream you have installed. BuildStream 1 will load it's configuration
+   from ``$XDG_CONFIG_HOME/buildstream1.conf`` and BuildStream 2 will load
+   it's configuration from ``$XDG_CONFIG_HOME/buildstream2.conf``, while
+   any version will fallback to ``$XDG_CONFIG_HOME/buildstream.conf``.
+
 
 Project specific value
 ----------------------
diff --git a/src/buildstream/_context.py b/src/buildstream/_context.py
index 090b3e0bc..19e0781c1 100644
--- a/src/buildstream/_context.py
+++ b/src/buildstream/_context.py
@@ -219,9 +219,17 @@ class Context:
         # a $XDG_CONFIG_HOME/buildstream.conf file
         #
         if not config:
-            default_config = os.path.join(os.environ["XDG_CONFIG_HOME"], "buildstream.conf")
-            if os.path.exists(default_config):
-                config = default_config
+            #
+            # Support parallel installations of BuildStream by first
+            # trying a (major point) version specific configuration file
+            # and then falling back to buildstream.conf.
+            #
+            major_version, _ = utils._get_bst_api_version()
+            for config_filename in ("buildstream{}.conf".format(major_version), "buildstream.conf"):
+                default_config = os.path.join(os.environ["XDG_CONFIG_HOME"], config_filename)
+                if os.path.exists(default_config):
+                    config = default_config
+                    break
 
         # Load default config
         #
diff --git a/tests/internals/context.py b/tests/internals/context.py
index a8b9f6dd3..9d06a68bf 100644
--- a/tests/internals/context.py
+++ b/tests/internals/context.py
@@ -5,6 +5,7 @@ import os
 import pytest
 
 from buildstream._context import Context
+from buildstream import _yaml, utils
 from buildstream._exceptions import LoadError
 from buildstream.exceptions import LoadErrorReason
 
@@ -80,6 +81,33 @@ def test_context_load_user_config(context_fixture, datafiles):
     assert context.logdir == os.path.join(cache_home, "buildstream", "logs")
 
 
+@pytest.mark.datafiles(os.path.join(DATA_DIR))
+def test_context_priority(datafiles):
+    confdir = os.path.join(str(datafiles), "config")
+    os.makedirs(confdir)
+
+    # The fallback (usual) config file
+    bst_conf_path = os.path.join(confdir, "buildstream.conf")
+    bst_conf = {"sourcedir": "/sources"}
+    _yaml.roundtrip_dump(bst_conf, bst_conf_path)
+
+    # The version specific config file
+    major_version, _ = utils._get_bst_api_version()
+    bst_conf_path = os.path.join(confdir, "buildstream{}.conf".format(major_version))
+    bst_conf = {"sourcedir": "/other_sources"}
+    _yaml.roundtrip_dump(bst_conf, bst_conf_path)
+
+    # Load the Context() object and assert that we've chosen
+    # the version specific one.
+    #
+    os.environ["XDG_CONFIG_HOME"] = confdir
+    with Context() as context:
+        context.load()
+        assert context.sourcedir == "/other_sources"
+
+    del os.environ["XDG_CONFIG_HOME"]
+
+
 #######################################
 #          Test failure modes         #
 #######################################