Merge lp:~jelmer/bzr-builddeb/multiple-upstream-tarballs-pt1 into lp:bzr-builddeb

[Jelmer Vernooij]

Initial work on supporting multiple upstream tarballs in bzr-builddeb.

This updates the UpstreamSource interface to return multiple paths for upstream tarballs and updates the AptSource and GetOrigSource implementations to actually return multiple tarballs.

Merging multiple upstream tarballs and extracting/committing multiple upstream tarballs in pristine tar branches are the next steps.

[James Westby (james-w)]

review: Approve

=== modified file 'cmds.py'
--- cmds.py	2011-06-03 12:17:42 +0000
+++ cmds.py	2011-06-14 14:11:23 +0000
@@ -69,6 +69,7 @@
     BuildFailedError,
     DchError,
     MissingChangelogError,
+    MultipleUpstreamTarballsNotSupported,
     NoPreviousUpload,
     PackageVersionNotPresent,
     StrictBuildFailed,
@@ -553,45 +554,50 @@
                     'merge had completed failed. Add the new changelog '
                     'entry yourself, review the merge, and then commit.')
 
-    def _do_merge(self, tree, tarball_filename, package, version,
+    def _do_merge(self, tree, tarball_filenames, package, version,
             current_version, upstream_branch, upstream_revision, merge_type,
             force):
         db = DistributionBranch(tree.branch, None, tree=tree)
         dbs = DistributionBranchSet()
         dbs.add_branch(db)
-        conflicts = db.merge_upstream(tarball_filename, package, version,
+        if len(tarball_filenames) > 1:
+            raise MultipleUpstreamTarballsNotSupported()
+        conflicts = db.merge_upstream(tarball_filenames[0], package, version,
                 current_version, upstream_branch=upstream_branch,
                 upstream_revision=upstream_revision,
                 merge_type=merge_type, force=force)
         return conflicts
 
-    def _fetch_tarball(self, package, version, orig_dir, location, v3):
+    def _fetch_tarball(self, package, version, orig_dir, locations, v3):
         from bzrlib.plugins.builddeb.repack_tarball import repack_tarball
+        ret = []
         format = None
-        if v3:
-            if location.endswith(".tar.bz2") or location.endswith(".tbz2"):
-                format = "bz2"
-        dest_name = tarball_name(package, version, format=format)
-        tarball_filename = os.path.join(orig_dir, dest_name)
-        try:
-            repack_tarball(location, dest_name, target_dir=orig_dir,
-                    force_gz=not v3)
-        except FileExists:
-            raise BzrCommandError("The target file %s already exists, and is either "
-                                  "different to the new upstream tarball, or they "
-                                  "are of different formats. Either delete the target "
-                                  "file, or use it as the argument to import."
-                                  % dest_name)
-        return tarball_filename
+        for location in locations:
+            if v3:
+                if location.endswith(".tar.bz2") or location.endswith(".tbz2"):
+                    format = "bz2"
+            dest_name = tarball_name(package, version, format=format)
+            tarball_filename = os.path.join(orig_dir, dest_name)
+            try:
+                repack_tarball(location, dest_name, target_dir=orig_dir,
+                        force_gz=not v3)
+            except FileExists:
+                raise BzrCommandError("The target file %s already exists, and is either "
+                                      "different to the new upstream tarball, or they "
+                                      "are of different formats. Either delete the target "
+                                      "file, or use it as the argument to import."
+                                      % dest_name)
+            ret.append(tarball_filename)
+        return ret
 
     def _get_tarball(self, config, tree, package, version, upstream_branch,
-            upstream_revision, v3, location):
+            upstream_revision, v3, locations):
         orig_dir = config.orig_dir or default_orig_dir
         orig_dir = os.path.join(tree.basedir, orig_dir)
         if not os.path.exists(orig_dir):
             os.makedirs(orig_dir)
         return self._fetch_tarball(package, version, orig_dir,
-            location, v3)
+            locations, v3)
 
     def _get_changelog_info(self, tree, last_version, package, distribution):
         current_version = last_version
@@ -738,15 +744,15 @@
                         (version, upstream_branch_source))
             if need_upstream_tarball:
                 target_dir = tempfile.mkdtemp() # FIXME: Cleanup?
-                location = primary_upstream_source.fetch_tarball(
+                locations = primary_upstream_source.fetch_tarball(
                     package, version, target_dir)
                 source_format = get_source_format(tree)
                 v3 = (source_format in [
                     FORMAT_3_0_QUILT, FORMAT_3_0_NATIVE])
-                tarball_filename = self._get_tarball(config, tree, package,
+                tarball_filenames = self._get_tarball(config, tree, package,
                     version, upstream_branch, upstream_revision, v3,
-                    location)
-                conflicts = self._do_merge(tree, tarball_filename, package,
+                    locations)
+                conflicts = self._do_merge(tree, tarball_filenames, package,
                     version, current_version, upstream_branch, upstream_revision,
                     merge_type, force)
             if current_version is not None and Version(current_version) >= Version(version):

=== modified file 'dh_make.py'
--- dh_make.py	2011-02-02 18:33:23 +0000
+++ dh_make.py	2011-06-14 14:11:23 +0000
@@ -13,6 +13,7 @@
 
 from bzrlib.plugins.builddeb import (
     default_orig_dir,
+    errors,
     import_dsc,
     upstream,
     util,
@@ -50,7 +51,7 @@
     return tree
 
 
-def _get_tarball(tree, tarball, package_name, version, use_v3=False):
+def _get_tarballs(tree, tarball, package_name, version, use_v3=False):
     from bzrlib.plugins.builddeb.repack_tarball import repack_tarball
     config = util.debuild_config(tree, tree)
     orig_dir = config.orig_dir or default_orig_dir
@@ -62,14 +63,16 @@
         if tarball.endswith(".tar.bz2") or tarball.endswith(".tbz2"):
             format = "bz2"
     dest_name = util.tarball_name(package_name, version, format=format)
-    tarball_filename = os.path.join(orig_dir, dest_name)
     trace.note("Fetching tarball")
     repack_tarball(tarball, dest_name, target_dir=orig_dir,
             force_gz=not use_v3)
     provider = upstream.UpstreamProvider(package_name, version,
             orig_dir, [])
-    provider.provide(os.path.join(tree.basedir, ".."))
-    return tarball_filename, util.md5sum_filename(tarball_filename)
+    orig_files = provider.provide(os.path.join(tree.basedir, ".."))
+    ret = []
+    for filename in orig_files:
+        ret.append((filename, util.md5sum_filename(filename)))
+    return ret
 
 
 def import_upstream(tarball, package_name, version, use_v3=False):
@@ -78,12 +81,15 @@
         parents = [tree.branch.last_revision()]
     else:
         parents = []
-    tarball_filename, md5sum = _get_tarball(tree, tarball,
+    tarball_filenames  = _get_tarballs(tree, tarball,
             package_name, version, use_v3=use_v3)
     db = import_dsc.DistributionBranch(tree.branch, tree.branch, tree=tree,
             upstream_tree=tree)
     dbs = import_dsc.DistributionBranchSet()
     dbs.add_branch(db)
+    if len(tarball_filenames) > 1:
+        raise errors.MultipleUpstreamTarballsNotSupported()
+    (tarball_filename, md5sum) = tarball_filenames[0]
     db.import_upstream_tarball(tarball_filename, version, parents, md5sum=md5sum)
     return tree
 

=== modified file 'errors.py'
--- errors.py	2011-06-09 21:43:07 +0000
+++ errors.py	2011-06-14 14:11:23 +0000
@@ -34,10 +34,11 @@
 
 
 class MissingUpstreamTarball(BzrError):
-    _fmt = "Unable to find the needed upstream tarball: %(tarball_name)s."
+    _fmt = ("Unable to find the needed upstream tarball for package %(package)s, "
+            "version %(version)s.")
 
-    def __init__(self, tarball_name):
-        BzrError.__init__(self, tarball_name=tarball_name)
+    def __init__(self, package, version):
+        BzrError.__init__(self, package=package, version=version)
 
 
 class TarFailed(BzrError):

=== modified file 'source_distiller.py'
--- source_distiller.py	2010-03-11 23:44:57 +0000
+++ source_distiller.py	2011-06-14 14:11:23 +0000
@@ -26,6 +26,7 @@
 from bzrlib import errors as bzr_errors
 
 from bzrlib.plugins.builddeb.errors import (
+        MultipleUpstreamTarballsNotSupported,
         TarFailed,
         )
 from bzrlib.plugins.builddeb.util import (
@@ -121,11 +122,14 @@
         if parent_dir != '' and not os.path.exists(parent_dir):
             os.makedirs(parent_dir)
         if not self.use_existing:
-            tarball = self.upstream_provider.provide(parent_dir)
+            tarballs = self.upstream_provider.provide(parent_dir)
+            if len(tarballs) > 1:
+                raise MultipleUpstreamTarballsNotSupported()
+            tarball = tarballs[0]
             # Extract it to the right place
             tempdir = tempfile.mkdtemp(prefix='builddeb-merge-')
             try:
-                ret = subprocess.call(['tar','-C',tempdir,'-xf',tarball],
+                ret = subprocess.call(['tar', '-C', tempdir, '-xf', tarball],
                         preexec_fn=subprocess_setup)
                 if ret != 0:
                     raise TarFailed("uncompress", tarball)

=== modified file 'tests/test_upstream.py'
--- tests/test_upstream.py	2011-06-14 00:32:04 +0000
+++ tests/test_upstream.py	2011-06-14 14:11:23 +0000
@@ -186,6 +186,21 @@
         self.assertEqual("apackage", sources.lookup_package)
         self.assertEqual(0, caller.called)
 
+    def test_apt_provider_multiple_tarballs(self):
+        caller = MockAptCaller(work=True)
+        sources = MockSources(["0.1-1", "0.2-1"],
+            [[("checksum", 0L, "apackage_0.1.orig.tar.gz", "tar")],
+             [("checksum", 0L, "apackage_0.2.orig.tar.bz2", "tar"),
+              ("checksum", 1L, "apackage_0.2.orig-extra.tar.gz", "tar")]])
+        apt_pkg = MockAptPkg(sources)
+        src = AptSource()
+        src._run_apt_source = caller.call
+        paths = src.fetch_tarball("apackage", "0.2", "target",
+            _apt_pkg=apt_pkg)
+        self.assertEquals(paths, [
+            "target/apackage_0.2.orig.tar.bz2",
+            "target/apackage_0.2.orig-extra.tar.gz"])
+
     def test_apt_provider_right_version_bz2(self):
         caller = MockAptCaller(work=True)
         sources = MockSources(["0.1-1", "0.2-1"],
@@ -194,10 +209,9 @@
         apt_pkg = MockAptPkg(sources)
         src = AptSource()
         src._run_apt_source = caller.call
-        path = src.fetch_tarball("apackage", "0.2", "target",
+        paths = src.fetch_tarball("apackage", "0.2", "target",
             _apt_pkg=apt_pkg)
-        self.assertEquals(path,
-            "target/apackage_0.2.orig.tar.bz2")
+        self.assertEquals(paths, ["target/apackage_0.2.orig.tar.bz2"])
 
     def test_apt_provider_right_version(self):
         caller = MockAptCaller(work=True)
@@ -207,10 +221,9 @@
         apt_pkg = MockAptPkg(sources)
         src = AptSource()
         src._run_apt_source = caller.call
-        path = src.fetch_tarball("apackage", "0.2", "target",
+        paths = src.fetch_tarball("apackage", "0.2", "target",
             _apt_pkg=apt_pkg)
-        self.assertEquals(path,
-            "target/apackage_0.2.orig.tar.gz")
+        self.assertEquals(paths, ["target/apackage_0.2.orig.tar.gz"])
         self.assertEqual(1, apt_pkg.init_called_times)
         self.assertEqual(1, apt_pkg.get_pkg_source_records_called_times)
         self.assertEqual(1, sources.restart_called_times)
@@ -276,7 +289,7 @@
         self._specific_versions.append((package, version, target_dir))
         if not self._succeed:
             raise PackageVersionNotPresent(package, version, self)
-        return self._tarball_path(package, version, target_dir)
+        return [self._tarball_path(package, version, target_dir)]
 
     def __repr__(self):
         return "%s()" % self.__class__.__name__
@@ -377,7 +390,7 @@
         source = UpstreamBranchSource(self.tree.branch,
             {"1.0": self.tree.branch.last_revision()})
         os.mkdir("mydir")
-        self.assertEquals("mydir/foo_1.0.orig.tar.gz",
+        self.assertEquals(["mydir/foo_1.0.orig.tar.gz"],
             source.fetch_tarball("foo", "1.0", "mydir"))
         self.assertPathExists("mydir/foo_1.0.orig.tar.gz")
 
@@ -443,7 +456,7 @@
             {"1.0": self.tree.branch.last_revision()})
         self.assertIs(None, source._upstream_branch)
         os.mkdir("mydir")
-        self.assertEquals("mydir/foo_1.0.orig.tar.gz",
+        self.assertEquals(["mydir/foo_1.0.orig.tar.gz"],
             source.fetch_tarball("foo", "1.0", "mydir"))
         self.assertPathExists("mydir/foo_1.0.orig.tar.gz")
         self.assertIsNot(None, source._upstream_branch)
@@ -721,7 +734,7 @@
     def test_fetch_tarball(self):
         source = TarfileSource("foo-1.0.tar.gz", "1.0")
         os.mkdir("bar")
-        self.assertEquals("bar/foo_1.0.orig.tar.gz",
+        self.assertEquals(["bar/foo_1.0.orig.tar.gz"],
             source.fetch_tarball("foo", "1.0", "bar"))
         self.assertPathExists("bar/foo_1.0.orig.tar.gz")
 
@@ -731,7 +744,7 @@
         zf.close()
         source = TarfileSource("bla-2.0.zip", "2.0")
         os.mkdir("bar")
-        self.assertEquals("bar/foo_2.0.orig.tar.gz",
+        self.assertEquals(["bar/foo_2.0.orig.tar.gz"],
             source.fetch_tarball("foo", "2.0", "bar"))
         self.assertPathExists("bar/foo_2.0.orig.tar.gz")
 
@@ -748,7 +761,7 @@
         bz2.BZ2File("foo-1.0.tar.bz2").close()
         source = TarfileSource("foo-1.0.tar.bz2", "1.0")
         os.mkdir("bar")
-        self.assertEquals("bar/foo_1.0.orig.tar.gz",
+        self.assertEquals(["bar/foo_1.0.orig.tar.gz"],
             source.fetch_tarball("foo", "1.0", "bar"))
         self.assertPathExists("bar/foo_1.0.orig.tar.gz")
         gzip.open("bar/foo_1.0.orig.tar.gz").close()
@@ -761,7 +774,7 @@
         pass
 
     def provide(self, target_dir):
-        raise MissingUpstreamTarball("test_tarball")
+        raise MissingUpstreamTarball("test_tarball", "1.0")
 
 
 class _TouchUpstreamProvider(UpstreamProvider):
@@ -771,9 +784,11 @@
         self.desired_tarball_name = desired_tarball_name
 
     def provide(self, target_dir):
-        f = open(os.path.join(target_dir, self.desired_tarball_name), "wb")
+        path = os.path.join(target_dir, self.desired_tarball_name)
+        f = open(path, "wb")
         f.write("I am a tarball, honest\n")
         f.close()
+        return [path]
 
 
 class _SimpleUpstreamProvider(UpstreamProvider):
@@ -785,11 +800,11 @@
         self.store_dir = store_dir
 
     def provide(self, target_dir):
-        path = (self.already_exists_in_target(target_dir)
+        paths = (self.already_exists_in_target(target_dir)
                 or self.provide_from_store_dir(target_dir))
-        if path is not None:
-            return path
-        raise MissingUpstreamTarball(self._tarball_names()[0])
+        if paths is not None:
+            return paths
+        raise MissingUpstreamTarball(self.package, self.version)
 
 
 class ExtractTarballVersionTests(TestCase):

=== modified file 'upstream/__init__.py'
--- upstream/__init__.py	2011-06-13 22:10:22 +0000
+++ upstream/__init__.py	2011-06-14 14:11:23 +0000
@@ -85,7 +85,7 @@
         :param package: Name of the package
         :param version: Version string of the version to fetch
         :param target_dir: Directory in which to store the tarball
-        :return: Path of the fetched tarball
+        :return: Paths of the fetched tarballs
         """
         raise NotImplementedError(self.fetch_tarball)
 
@@ -126,14 +126,17 @@
         lookup = get_fn(sources, 'lookup', 'Lookup')
         while lookup(package):
             version = get_fn(sources, 'version', 'Version')
+            filenames = []
             for (checksum, size, filename, filekind) in sources.files:
                 if filekind != "tar":
                     continue
                 filename = os.path.basename(filename)
                 if filename.startswith("%s_%s.orig" % (package, upstream_version)):
-                    if self._run_apt_source(package, version, target_dir):
-                        return os.path.join(target_dir, filename)
-                break
+                    filenames.append(filename)
+            if filenames:
+                if self._run_apt_source(package, version, target_dir):
+                    return [os.path.join(target_dir, filename)
+                            for filename in filenames]
         note("apt could not find the needed tarball.")
         raise PackageVersionNotPresent(package, upstream_version, self)
 
@@ -157,8 +160,7 @@
         self.tree = tree
         self.larstiq = larstiq
 
-    def _get_orig_source(self, source_dir, desired_tarball_names,
-                        target_dir):
+    def _get_orig_source(self, source_dir, prefix, target_dir):
         note("Trying to use get-orig-source to retrieve needed tarball.")
         command = ["make", "-f", "debian/rules", "get-orig-source"]
         proc = subprocess.Popen(command, cwd=source_dir)
@@ -166,13 +168,18 @@
         if ret != 0:
             note("Trying to run get-orig-source rule failed")
             return None
-        for desired_tarball_name in desired_tarball_names:
-            fetched_tarball = os.path.join(source_dir, desired_tarball_name)
+        filenames = []
+        for filename in os.listdir(source_dir):
+            if not filename.startswith(prefix):
+                continue
+            fetched_tarball = os.path.join(source_dir, filename)
             if os.path.exists(fetched_tarball):
-                repack_tarball(fetched_tarball, desired_tarball_name,
+                repack_tarball(fetched_tarball, filename,
                                target_dir=target_dir, force_gz=False)
-                return fetched_tarball
-        note("get-orig-source did not create %s", desired_tarball_name)
+                filenames.append(os.path.join(target_dir, filename))
+        if filenames:
+            return filenames
+        note("get-orig-source did not create file with prefix %s", prefix)
         return None
 
     def fetch_tarball(self, package, version, target_dir):
@@ -182,9 +189,6 @@
             rules_name = 'debian/rules'
         rules_id = self.tree.path2id(rules_name)
         if rules_id is not None:
-            desired_tarball_names = [tarball_name(package, version),
-                    tarball_name(package, version, 'bz2'),
-                    tarball_name(package, version, 'lzma')]
             tmpdir = tempfile.mkdtemp(prefix="builddeb-get-orig-source-")
             try:
                 base_export_dir = os.path.join(tmpdir, "export")
@@ -193,11 +197,11 @@
                     os.mkdir(export_dir)
                     export_dir = os.path.join(export_dir, "debian")
                 export(self.tree, export_dir, format="dir")
-                tarball_path = self._get_orig_source(base_export_dir,
-                        desired_tarball_names, target_dir)
-                if tarball_path is None:
+                tarball_paths = self._get_orig_source(base_export_dir,
+                        "%s_%s.orig" % (package, version), target_dir)
+                if tarball_paths is None:
                     raise PackageVersionNotPresent(package, version, self)
-                return tarball_path
+                return tarball_paths
             finally:
                 shutil.rmtree(tmpdir)
         note("No debian/rules file to try and use for a get-orig-source rule")
@@ -279,7 +283,7 @@
         if r != 0:
             note("uscan could not find the needed tarball.")
             raise PackageVersionNotPresent(package, version, self)
-        return self._tarball_path(package, version, target_dir)
+        return [self._tarball_path(package, version, target_dir)]
 
 
 class SelfSplitSource(UpstreamSource):
@@ -307,13 +311,13 @@
                 "to create the tarball")
         tarball_path = self._tarball_path(package, version, target_dir)
         self._split(package, version, tarball_path)
-        return tarball_path
+        return [tarball_path]
 
 
 class StackedUpstreamSource(UpstreamSource):
     """An upstream source that checks a list of other upstream sources.
 
-    The first source that can provide a tarball, wins. 
+    The first source that can provide a tarball, wins.
     """
 
     def __init__(self, sources):
@@ -325,12 +329,11 @@
     def fetch_tarball(self, package, version, target_dir):
         for source in self._sources:
             try:
-                path = source.fetch_tarball(package, version, target_dir)
+                paths = source.fetch_tarball(package, version, target_dir)
             except PackageVersionNotPresent:
                 pass
             else:
-                assert isinstance(path, basestring)
-                return path
+                return paths
         raise PackageVersionNotPresent(package, version, self)
 
     def get_latest_version(self, package, version):
@@ -364,7 +367,7 @@
         self.source = StackedUpstreamSource(sources)
 
     def provide(self, target_dir):
-        """Provide the upstream tarball any way possible.
+        """Provide the upstream tarball(s) any way possible.
 
         Call this to place the correctly named tarball in to target_dir,
         through means possible.
@@ -396,44 +399,45 @@
             if not os.path.exists(self.store_dir):
                 os.makedirs(self.store_dir)
             try:
-                path = self.source.fetch_tarball(self.package,
+                paths = self.source.fetch_tarball(self.package,
                     self.version, self.store_dir)
             except PackageVersionNotPresent:
-                raise MissingUpstreamTarball(self._tarball_names()[0])
-            assert isinstance(path, basestring)
+                raise MissingUpstreamTarball(self.package, self.version)
+            assert isinstance(paths, list)
         else:
             note("Using the upstream tarball that is present in %s" %
                  self.store_dir)
-        path = self.provide_from_store_dir(target_dir)
-        assert path is not None
-        return path
+        paths = self.provide_from_store_dir(target_dir)
+        assert paths is not None
+        return paths
+
+    def _gather_orig_files(self, path):
+        prefix = "%s_%s.orig" % (self.package, self.version)
+        ret = []
+        path = os.path.abspath(path)
+        if not os.path.isdir(path):
+            return None
+        for filename in os.listdir(path):
+            if filename.startswith(prefix):
+                ret.append(os.path.join(path, filename))
+        if ret:
+            return ret
+        return None
 
     def already_exists_in_target(self, target_dir):
-        for tarball_name in self._tarball_names():
-            path = os.path.join(target_dir, tarball_name)
-            if os.path.exists(path):
-                return path
-        return None
+        return self._gather_orig_files(target_dir)
 
     def already_exists_in_store(self):
-        for tarball_name in self._tarball_names():
-            path = os.path.join(self.store_dir, tarball_name)
-            if os.path.exists(path):
-                return path
-        return None
+        return self._gather_orig_files(self.store_dir)
 
     def provide_from_store_dir(self, target_dir):
-        path = self.already_exists_in_store()
-        if path is not None:
+        paths = self.already_exists_in_store()
+        if paths is None:
+            return None
+        for path in paths:
             repack_tarball(path, os.path.basename(path),
                     target_dir=target_dir, force_gz=False)
-            return path
-        return path
-
-    def _tarball_names(self):
-        return [tarball_name(self.package, self.version),
-                tarball_name(self.package, self.version, format='bz2'),
-                tarball_name(self.package, self.version, format='lzma')]
+        return paths
 
 
 def extract_tarball_version(path, packagename):
@@ -473,7 +477,7 @@
             raise PackageVersionNotPresent(package, version, self)
         dest_name = tarball_name(package, version)
         repack_tarball(self.path, dest_name, target_dir=target_dir, force_gz=True)
-        return os.path.join(target_dir, dest_name)
+        return [os.path.join(target_dir, dest_name)]
 
     def get_latest_version(self, package, version):
         if self.version is not None:

=== modified file 'upstream/branch.py'
--- upstream/branch.py	2011-04-28 15:46:43 +0000
+++ upstream/branch.py	2011-06-14 14:11:23 +0000
@@ -268,7 +268,7 @@
             export(rev_tree, target_filename, 'tgz', tarball_base)
         finally:
             self.upstream_branch.unlock()
-        return target_filename
+        return [target_filename]
 
     def __repr__(self):
         return "<%s for %r>" % (self.__class__.__name__,

=== modified file 'upstream/pristinetar.py'
--- upstream/pristinetar.py	2011-06-03 12:34:57 +0000
+++ upstream/pristinetar.py	2011-06-14 14:11:23 +0000
@@ -145,7 +145,7 @@
             raise PackageVersionNotPresent(package, version, self)
         except PerFileTimestampsNotSupported:
             raise PackageVersionNotPresent(package, version, self)
-        return target_filename
+        return [target_filename]
 
     def _has_version(self, tag_name, md5=None):
         if not self.branch.tags.has_tag(tag_name):