Merge lp:~james-w/linaro-image-tools/set-installed-packages into lp:linaro-image-tools/11.11

[James Westby]

Hi,

This one relies on the internals of dpkg to some extent, but not really
any more than we already are, and I'm not sure of the last time that this
area actually changed.

What we are doing is allowing the caller to pretend that a list of packages
are installed, which will come in handy later.

We do this by writing the /var/lib/dpkg/status file with the package info
that apt would install if we asked it to install these packages (so includes
dependencies).

Unfortunately apt has no way to do this short of actually installing the
packages, which we certainly don't want to do.

Thanks,

James

[Zygmunt Krynicki (zyga)]

Looks good.

I would also look at adding the test for reopen=False but I don't think that's really needed.

review: Approve

=== modified file 'hwpack/packages.py'
--- hwpack/packages.py	2010-09-13 21:31:05 +0000
+++ hwpack/packages.py	2010-09-13 21:31:06 +0000
@@ -242,8 +242,6 @@
         """
         self.cleanup()
         self.tempdir = tempfile.mkdtemp(prefix="hwpack-apt-cache-")
-        files = ["var/lib/dpkg/status",
-                ]
         dirs = ["var/lib/dpkg",
                 "etc/apt/",
                 "var/cache/apt/archives/partial",
@@ -251,9 +249,7 @@
                ]
         for d in dirs:
             os.makedirs(os.path.join(self.tempdir, d))
-        for fn in files:
-            with open(os.path.join(self.tempdir, fn), 'w'):
-                pass
+        self.set_installed_packages([], reopen=False)
         sources_list = os.path.join(
             self.tempdir, "etc", "apt", "sources.list")
         with open(sources_list, 'w') as f:
@@ -268,6 +264,28 @@
         self.cache.open()
         return self
 
+    def set_installed_packages(self, packages, reopen=True):
+        """Set a list of packages as those installed on the system.
+
+        This does no installing, just changes dpkg's database to have
+        the tools think the packages are installed.
+
+        :param packages: a list of packages to "install" on the system,
+            replacing any others.
+        :type packages: an iterable of FetchedPackages.
+        :param reopen: whether to reopen the apt cache after doing the
+            operation. Default is to do so. Note that if it is not done,
+            then the changes will not be visible in the cache until it
+            is reopened.
+        """
+        with open(
+            os.path.join(self.tempdir, "var/lib/dpkg/status"), "w") as f:
+            f.write(
+                get_packages_file(
+                    packages, extra_text="Status: install ok installed"))
+        if reopen:
+            self.cache.open()
+
     __enter__ = prepare
 
     def cleanup(self):

=== modified file 'hwpack/tests/test_packages.py'
--- hwpack/tests/test_packages.py	2010-09-13 21:31:05 +0000
+++ hwpack/tests/test_packages.py	2010-09-13 21:31:06 +0000
@@ -481,6 +481,28 @@
             self.assertTrue(os.path.isdir(tempdir))
         self.assertFalse(os.path.exists(tempdir))
 
+    def test_set_installed_packages(self):
+        cache = IsolatedAptCache([])
+        self.addCleanup(cache.cleanup)
+        cache.prepare()
+        packages = [DummyFetchedPackage("foo", "1.0")]
+        cache.set_installed_packages(packages)
+        self.assertEqual(
+            get_packages_file(
+                packages, extra_text="Status: install ok installed"),
+            open(os.path.join(
+                cache.tempdir, "var", "lib", "dpkg", "status")).read())
+
+    def test_set_installed_packages_empty_list(self):
+        cache = IsolatedAptCache([])
+        self.addCleanup(cache.cleanup)
+        cache.prepare()
+        cache.set_installed_packages([])
+        self.assertEqual(
+            "",
+            open(os.path.join(
+                cache.tempdir, "var", "lib", "dpkg", "status")).read())
+
 
 class PackageFetcherTests(TestCaseWithFixtures):