_artifactcache.py: Raise ArtifactError() when quota size exceeds disk space.

This is not an error related to loading data, like a parse error
in the quota specification is, but a problem raised by the artifact
cache - this allows us to assert more specific machine readable
errors in test cases (instead of checking the string in stderr, which
this patch also fixes).

This also removes a typo from the error message in the said error.

  * tests/artifactcache/cache_size.py

    Updated test case to expect the artifact error, which consequently
    changes the test case to properly assert a machine readable error
    instead of asserting text in the stderr (which is the real, secret
    motivation behind this patch).

  * tests/artifactcache/expiry.py: Reworked test_invalid_cache_quota()

    Now expect the artifact error for the tests which check configurations
    which create caches too large to fit on the disk.

3 files changed, 40 insertions, 20 deletions

diff --git a/buildstream/_artifactcache/artifactcache.py b/buildstream/_artifactcache/artifactcache.py
index 53f7708d6..bc2150c1b 100644
--- a/buildstream/_artifactcache/artifactcache.py
+++ b/buildstream/_artifactcache/artifactcache.py
@@ -699,15 +699,22 @@ class ArtifactCache():
                             "Invalid cache quota ({}): ".format(utils._pretty_size(cache_quota)) +
                             "BuildStream requires a minimum cache quota of 2G.")
         elif cache_quota > cache_size + available_space:  # Check maximum
-            raise LoadError(LoadErrorReason.INVALID_DATA,
-                            ("Your system does not have enough available " +
-                             "space to support the cache quota specified.\n" +
-                             "You currently have:\n" +
-                             "- {used} of cache in use at {local_cache_path}\n" +
-                             "- {available} of available system storage").format(
-                                 used=utils._pretty_size(cache_size),
-                                 local_cache_path=self.context.artifactdir,
-                                 available=utils._pretty_size(available_space)))
+            if '%' in self.context.config_cache_quota:
+                available = (available_space / total_size) * 100
+                available = '{}% of total disk space'.format(round(available, 1))
+            else:
+                available = utils._pretty_size(available_space)
+
+            raise ArtifactError("Your system does not have enough available " +
+                                "space to support the cache quota specified.",
+                                detail=("You have specified a quota of {quota} total disk space.\n" +
+                                        "The filesystem containing {local_cache_path} only " +
+                                        "has {available_size} available.")
+                                .format(
+                                    quota=self.context.config_cache_quota,
+                                    local_cache_path=self.context.artifactdir,
+                                    available_size=available),
+                                reason='insufficient-storage-for-quota')
 
         # Place a slight headroom (2e9 (2GB) on the cache_quota) into
         # cache_quota to try and avoid exceptions.
diff --git a/tests/artifactcache/cache_size.py b/tests/artifactcache/cache_size.py
index 8e47f9fb6..63ab9ad07 100644
--- a/tests/artifactcache/cache_size.py
+++ b/tests/artifactcache/cache_size.py
@@ -1,8 +1,10 @@
 import os
 import pytest
+from unittest import mock
 
 from buildstream import _yaml
 from buildstream._artifactcache import CACHE_SIZE_FILE
+from buildstream._exceptions import ErrorDomain
 
 from tests.testutils import cli, create_element_size
 
diff --git a/tests/artifactcache/expiry.py b/tests/artifactcache/expiry.py
index 68a1c87cd..ce8e6c9e8 100644
--- a/tests/artifactcache/expiry.py
+++ b/tests/artifactcache/expiry.py
@@ -1,6 +1,7 @@
 import os
 
 import pytest
+from unittest import mock
 
 from buildstream import _yaml
 from buildstream._exceptions import ErrorDomain, LoadErrorReason
@@ -282,18 +283,28 @@ def test_never_delete_required_track(cli, datafiles, tmpdir):
 
 # Ensure that only valid cache quotas make it through the loading
 # process.
-@pytest.mark.parametrize("quota,success", [
-    ("1", True),
-    ("1K", True),
-    ("50%", True),
-    ("infinity", True),
-    ("0", True),
-    ("-1", False),
-    ("pony", False),
-    ("200%", False)
+#
+# This test virtualizes the condition to assume a storage volume
+# has 10K total disk space, and 6K of it is already in use (not
+# including any space used by the artifact cache).
+#
+@pytest.mark.parametrize("quota,err_domain,err_reason", [
+    # Valid configurations
+    ("1", 'success', None),
+    ("1K", 'success', None),
+    ("50%", 'success', None),
+    ("infinity", 'success', None),
+    ("0", 'success', None),
+    # Invalid configurations
+    ("-1", ErrorDomain.LOAD, LoadErrorReason.INVALID_DATA),
+    ("pony", ErrorDomain.LOAD, LoadErrorReason.INVALID_DATA),
+    ("200%", ErrorDomain.LOAD, LoadErrorReason.INVALID_DATA),
+    # Not enough space for these caches
+    ("7K", ErrorDomain.ARTIFACT, 'insufficient-storage-for-quota'),
+    ("70%", ErrorDomain.ARTIFACT, 'insufficient-storage-for-quota')
 ])
 @pytest.mark.datafiles(DATA_DIR)
-def test_invalid_cache_quota(cli, datafiles, tmpdir, quota, success):
+def test_invalid_cache_quota(cli, datafiles, tmpdir, quota, err_domain, err_reason):
     project = os.path.join(datafiles.dirname, datafiles.basename)
     os.makedirs(os.path.join(project, 'elements'))
 
@@ -335,7 +346,7 @@ def test_invalid_cache_quota(cli, datafiles, tmpdir, quota, success):
     if err_domain == 'success':
         res.assert_success()
     else:
-        res.assert_main_error(ErrorDomain.LOAD, LoadErrorReason.INVALID_DATA)
+        res.assert_main_error(err_domain, err_reason)
 
 
 @pytest.mark.datafiles(DATA_DIR)