Merge ~twom/launchpad:buildd-sha-export into launchpad:master

[Tom Wardill]

Add retrieval of the sha256 for a chroot in a DAS

We set the chroot for a PocketChroot via the DistroArchSeries using it's SHA1, but this is basically write-only without downloading the whole chroot file and recalculating it.
Add an equivalent getChrootHash alongside getChrootURL that returns the sha256 from the librarian file.

Sample API call:
https://api.launchpad.test/devel/ubuntu/bionic/amd64?ws.op=getChrootHash&image_type=Chroot%20tarball&pocket=Release

[Colin Watson (cjwatson)]

This broadly looks good, but I'd like some small API adjustments.

review: Needs Fixing

[Colin Watson (cjwatson)]

review: Approve

diff --git a/lib/lp/soyuz/browser/tests/test_distroarchseries_webservice.py b/lib/lp/soyuz/browser/tests/test_distroarchseries_webservice.py
index 32cd64e..c9e6db4 100644
--- a/lib/lp/soyuz/browser/tests/test_distroarchseries_webservice.py
+++ b/lib/lp/soyuz/browser/tests/test_distroarchseries_webservice.py
@@ -14,6 +14,7 @@ from lazr.restfulclient.errors import (
 from testtools.matchers import (
     EndsWith,
     Equals,
+    MatchesDict,
     MatchesStructure,
     )
 from zope.security.management import endInteraction
@@ -120,6 +121,19 @@ class TestDistroArchSeriesWebservice(TestCaseWithFactory):
             data=b'foo\r', sha1sum='95e0c0e09be59e04eb0e312e5daa11a2a830e526')
         self.assertEqual(sha1, das.getChroot().content.sha1)
 
+    def test_getChrootHash(self):
+        das = self.factory.makeDistroArchSeries()
+        user = das.distroseries.distribution.main_archive.owner
+        webservice = launchpadlib_for("testing", user)
+        ws_das = ws_object(webservice, das)
+        sha1 = hashlib.sha1('abcxyz').hexdigest()
+        sha256 = hashlib.sha256('abcxyz').hexdigest()
+        ws_das.setChroot(data=b'abcxyz', sha1sum=sha1)
+        self.assertThat(
+            das.getChrootHash(
+                PackagePublishingPocket.RELEASE, BuildBaseImageType.CHROOT),
+            MatchesDict({'sha256': Equals(sha256)}))
+
     def test_setChroot_removeChroot(self):
         das = self.factory.makeDistroArchSeries()
         user = das.distroseries.distribution.main_archive.owner
diff --git a/lib/lp/soyuz/interfaces/distroarchseries.py b/lib/lp/soyuz/interfaces/distroarchseries.py
index d287840..4f70996 100644
--- a/lib/lp/soyuz/interfaces/distroarchseries.py
+++ b/lib/lp/soyuz/interfaces/distroarchseries.py
@@ -214,6 +214,14 @@ class IDistroArchSeriesPublic(IHasBuildRecords, IHasOwner):
         tarball".
         """
 
+    @operation_parameters(
+        pocket=Choice(vocabulary=PackagePublishingPocket, required=True),
+        image_type=Choice(vocabulary=BuildBaseImageType, required=True))
+    @export_read_operation()
+    @operation_for_version("devel")
+    def getChrootHash(pocket, image_type):
+        """Return the sha1sum of the current chroot for the given pocket."""
+
     def addOrUpdateChroot(chroot, pocket=None, image_type=None):
         """Return the just added or modified PocketChroot.
 
diff --git a/lib/lp/soyuz/model/distroarchseries.py b/lib/lp/soyuz/model/distroarchseries.py
index aedbe7c..ea8d5ee 100644
--- a/lib/lp/soyuz/model/distroarchseries.py
+++ b/lib/lp/soyuz/model/distroarchseries.py
@@ -175,6 +175,13 @@ class DistroArchSeries(SQLBase):
             return None
         return chroot.http_url
 
+    def getChrootHash(self, pocket, image_type):
+        """See `IDistroArchSeries`."""
+        chroot = self.getChroot(pocket=pocket, image_type=image_type)
+        if chroot is None:
+            return None
+        return {"sha256": chroot.content.sha256}
+
     @property
     def chroot_url(self):
         """See `IDistroArchSeries`."""