Add pip source plugin

`pip` source plugin can stage python packages that are either specified
directly in the element definition or picked up from `requirements.txt`
from previous sources. In order to support the latter use-case
(which is also the primary motivation for this plugin), this plugin
requires access to previous sources and hence is an example of a
Source Transform source.

Also, bump `BST_FORMAT_VERSION` as this patch adds a new core plugin.

22 files changed, 454 insertions, 6 deletions

diff --git a/buildstream/_versions.py b/buildstream/_versions.py
index a722e11a5..713cb9d67 100644
--- a/buildstream/_versions.py
+++ b/buildstream/_versions.py
@@ -23,7 +23,7 @@
 # This version is bumped whenever enhancements are made
 # to the `project.conf` format or the core element format.
 #
-BST_FORMAT_VERSION = 15
+BST_FORMAT_VERSION = 16
 
 
 # The base BuildStream artifact version
diff --git a/buildstream/plugins/sources/pip.py b/buildstream/plugins/sources/pip.py
new file mode 100644
index 000000000..18e65c73d
--- /dev/null
+++ b/buildstream/plugins/sources/pip.py
@@ -0,0 +1,237 @@
+#
+#  Copyright 2018 Bloomberg Finance LP
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU Lesser General Public
+#  License as published by the Free Software Foundation; either
+#  version 2 of the License, or (at your option) any later version.
+#
+#  This library is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+#  Lesser General Public License for more details.
+#
+#  You should have received a copy of the GNU Lesser General Public
+#  License along with this library. If not, see <http://www.gnu.org/licenses/>.
+#
+#  Authors:
+#        Chandan Singh <csingh43@bloomberg.net>
+
+"""
+pip - stage python packages using pip
+=====================================
+
+**Host depndencies:**
+
+  * ``pip`` python module
+
+This plugin will download source distributions for specified packages using
+``pip`` but will not install them. It is expected that the elements using this
+source will install the downloaded packages.
+
+Downloaded tarballs will be stored in a directory called ".bst_pip_downloads".
+
+**Usage:**
+
+.. code:: yaml
+
+   # Specify the pip source kind
+   kind: pip
+
+   # Optionally specify index url, defaults to PyPi
+   # This url is used to discover new versions of packages and download them
+   # Projects intending to mirror their sources to a permanent location should
+   # use an aliased url, and declare the alias in the project configuration
+   url: https://mypypi.example.com/simple
+
+   # Optionally specify the path to requirements files
+   # Note that either 'requirements-files' or 'packages' must be defined
+   requirements-files:
+   - requirements.txt
+
+   # Optionally specify a list of additional packages
+   # Note that either 'requirements-files' or 'packages' must be defined
+   packages:
+   - flake8
+
+   # Optionally specify a relative staging directory
+   directory: path/to/stage
+
+   # Specify the ref. It is a list of strings of format
+   # "<package-name>==<version>", separated by "\\n".
+   # Usually this will be contents of a requirements.txt file where all
+   # package versions have been frozen.
+   ref: "flake8==3.5.0\\nmccabe==0.6.1\\npkg-resources==0.0.0\\npycodestyle==2.3.1\\npyflakes==1.6.0"
+
+.. note::
+
+   The ``pip`` plugin is available since :ref:`format version 16 <project_format_version>`
+
+"""
+
+import errno
+import hashlib
+import os
+import re
+
+from buildstream import Consistency, Source, SourceError, utils
+
+_OUTPUT_DIRNAME = '.bst_pip_downloads'
+_PYPI_INDEX_URL = 'https://pypi.org/simple/'
+
+# Used only for finding pip command
+_PYTHON_VERSIONS = [
+    'python2.7',
+    'python3.0',
+    'python3.1',
+    'python3.2',
+    'python3.3',
+    'python3.4',
+    'python3.5',
+    'python3.6',
+    'python3.7',
+]
+
+# List of allowed extensions taken from
+# https://docs.python.org/3/distutils/sourcedist.html.
+# Names of source distribution archives must be of the form
+# '%{package-name}-%{version}.%{extension}'.
+_SDIST_RE = re.compile(
+    r'^([a-zA-Z0-9]+?)-(.+).(?:tar|tar.bz2|tar.gz|tar.xz|tar.Z|zip)$',
+    re.IGNORECASE)
+
+
+class PipSource(Source):
+    # pylint: disable=attribute-defined-outside-init
+
+    # We need access to previous sources at track time to use requirements.txt
+    # but not at fetch time as self.ref should contain sufficient information
+    # for this plugin
+    BST_REQUIRES_PREVIOUS_SOURCES_TRACK = True
+
+    def configure(self, node):
+        self.node_validate(node, ['url', 'packages', 'ref', 'requirements-files'] +
+                           Source.COMMON_CONFIG_KEYS)
+        self.ref = self.node_get_member(node, str, 'ref', None)
+        self.original_url = self.node_get_member(node, str, 'url', _PYPI_INDEX_URL)
+        self.index_url = self.translate_url(self.original_url)
+        self.packages = self.node_get_member(node, list, 'packages', [])
+        self.requirements_files = self.node_get_member(node, list, 'requirements-files', [])
+
+        if not (self.packages or self.requirements_files):
+            raise SourceError("{}: Either 'packages' or 'requirements-files' must be specified". format(self))
+
+    def preflight(self):
+        # Try to find a pip version that supports download command
+        self.host_pip = None
+        for python in reversed(_PYTHON_VERSIONS):
+            try:
+                host_python = utils.get_host_tool(python)
+                rc = self.call([host_python, '-m', 'pip', 'download', '--help'])
+                if rc == 0:
+                    self.host_pip = [host_python, '-m', 'pip']
+                    break
+            except utils.ProgramNotFoundError:
+                pass
+
+        if self.host_pip is None:
+            raise SourceError("{}: Unable to find a suitable pip command".format(self))
+
+    def get_unique_key(self):
+        return [self.original_url, self.ref]
+
+    def get_consistency(self):
+        if not self.ref:
+            return Consistency.INCONSISTENT
+        if os.path.exists(self._mirror) and os.listdir(self._mirror):
+            return Consistency.CACHED
+        return Consistency.RESOLVED
+
+    def get_ref(self):
+        return self.ref
+
+    def load_ref(self, node):
+        self.ref = self.node_get_member(node, str, 'ref', None)
+
+    def set_ref(self, ref, node):
+        node['ref'] = self.ref = ref
+
+    def track(self, previous_sources_dir):
+        # XXX pip does not offer any public API other than the CLI tool so it
+        # is not feasible to correctly parse the requirements file or to check
+        # which package versions pip is going to install.
+        # See https://pip.pypa.io/en/stable/user_guide/#using-pip-from-your-program
+        # for details.
+        # As a result, we have to wastefully install the packages during track.
+        with self.tempdir() as tmpdir:
+            install_args = self.host_pip + ['download',
+                                            '--no-binary', ':all:',
+                                            '--index-url', self.index_url,
+                                            '--dest', tmpdir]
+            for requirement_file in self.requirements_files:
+                fpath = os.path.join(previous_sources_dir, requirement_file)
+                install_args += ['-r', fpath]
+            install_args += self.packages
+
+            self.call(install_args, fail="Failed to install python packages")
+            reqs = self._parse_sdist_names(tmpdir)
+
+        return '\n'.join(["{}=={}".format(pkg, ver) for pkg, ver in reqs])
+
+    def fetch(self):
+        with self.tempdir() as tmpdir:
+            packages = self.ref.strip().split('\n')
+            package_dir = os.path.join(tmpdir, 'packages')
+            os.makedirs(package_dir)
+            self.call(self.host_pip + ['download',
+                                       '--no-binary', ':all:',
+                                       '--index-url', self.index_url,
+                                       '--dest', package_dir] + packages,
+                      fail="Failed to install python packages: {}".format(packages))
+
+            # If the mirror directory already exists, assume that some other
+            # process has fetched the sources before us and ensure that we do
+            # not raise an error in that case.
+            try:
+                os.makedirs(self._mirror)
+                os.rename(package_dir, self._mirror)
+            except FileExistsError:
+                return
+            except OSError as e:
+                if e.errno != errno.ENOTEMPTY:
+                    raise
+
+    def stage(self, directory):
+        with self.timed_activity("Staging Python packages", silent_nested=True):
+            utils.copy_files(self._mirror, os.path.join(directory, _OUTPUT_DIRNAME))
+
+    # Directory where this source should stage its files
+    #
+    @property
+    def _mirror(self):
+        if not self.ref:
+            return None
+        return os.path.join(self.get_mirror_directory(),
+                            utils.url_directory_name(self.original_url),
+                            hashlib.sha256(self.ref.encode()).hexdigest())
+
+    # Parse names of downloaded source distributions
+    #
+    # Args:
+    #    basedir (str): Directory containing source distribution archives
+    #
+    # Returns:
+    #    (list): List of (package_name, version) tuples in sorted order
+    #
+    def _parse_sdist_names(self, basedir):
+        reqs = []
+        for f in os.listdir(basedir):
+            pkg_match = _SDIST_RE.match(f)
+            if pkg_match:
+                reqs.append(pkg_match.groups())
+
+        return sorted(reqs)
+
+
+def setup():
+    return PipSource
diff --git a/buildstream/source.py b/buildstream/source.py
index 7a0a0ec88..9822beeec 100644
--- a/buildstream/source.py
+++ b/buildstream/source.py
@@ -982,9 +982,9 @@ class Source(Plugin):
     #
     def __ensure_previous_sources(self, previous_sources):
         for index, src in enumerate(previous_sources):
+            # BuildStream should track sources in the order they appear so
+            # previous sources should never be in an inconsistent state
+            assert src.get_consistency() != Consistency.INCONSISTENT
+
             if src.get_consistency() == Consistency.RESOLVED:
                 src._fetch(previous_sources[0:index])
-            elif src.get_consistency() == Consistency.INCONSISTENT:
-                new_ref = src._track(previous_sources[0:index])
-                src._save_ref(new_ref)
-                src._fetch(previous_sources[0:index])
diff --git a/doc/source/core_plugins.rst b/doc/source/core_plugins.rst
index da7c607c8..c82ffe52f 100644
--- a/doc/source/core_plugins.rst
+++ b/doc/source/core_plugins.rst
@@ -58,6 +58,7 @@ Sources
    sources/ostree
    sources/patch
    sources/deb
+   sources/pip
 
 
 External plugins
diff --git a/tests/cachekey/project/sources/pip1.bst b/tests/cachekey/project/sources/pip1.bst
new file mode 100644
index 000000000..ee69efad6
--- /dev/null
+++ b/tests/cachekey/project/sources/pip1.bst
@@ -0,0 +1,12 @@
+kind: import
+
+sources:
+- kind: git
+  url: https://example.com/foo/foobar.git
+  ref: b99955530263172ed1beae52aed7a33885ef781f
+- kind: pip
+  url: https://pypi.example.com/simple
+  packages:
+  - horses
+  - ponies
+  ref: 'horses==0.0.1\nponies==0.0.2'
diff --git a/tests/cachekey/project/sources/pip1.expected b/tests/cachekey/project/sources/pip1.expected
new file mode 100644
index 000000000..11d7c5fae
--- /dev/null
+++ b/tests/cachekey/project/sources/pip1.expected
@@ -0,0 +1 @@
+880d0dc27d6683725cfd68d60156058115a9a53793b14b727fc6d0588a473763
\ No newline at end of file
diff --git a/tests/cachekey/project/target.bst b/tests/cachekey/project/target.bst
index 174215a49..d96645da8 100644
--- a/tests/cachekey/project/target.bst
+++ b/tests/cachekey/project/target.bst
@@ -13,6 +13,7 @@ depends:
 - sources/patch1.bst
 - sources/patch2.bst
 - sources/patch3.bst
+- sources/pip1.bst
 - sources/remote1.bst
 - sources/remote2.bst
 - sources/tar1.bst
diff --git a/tests/cachekey/project/target.expected b/tests/cachekey/project/target.expected
index d6d99895a..3c1cc261f 100644
--- a/tests/cachekey/project/target.expected
+++ b/tests/cachekey/project/target.expected
@@ -1 +1 @@
-e045df890262f7b7c663e64ad0bfba428d9d80ec514df3ddb13313d4ef669b73
\ No newline at end of file
+09620aa58875d96611d22632b7585a0f22f88f5ecca6f5d1915d3e529d036bd8
\ No newline at end of file
diff --git a/tests/integration/pip.py b/tests/integration/pip_element.py
index 6c6de8bf8..6c6de8bf8 100644
--- a/tests/integration/pip.py
+++ b/tests/integration/pip_element.py
diff --git a/tests/integration/pip_source.py b/tests/integration/pip_source.py
new file mode 100644
index 000000000..fc5b56a7c
--- /dev/null
+++ b/tests/integration/pip_source.py
@@ -0,0 +1,99 @@
+import os
+import pytest
+
+from buildstream import _yaml
+
+from tests.testutils import cli_integration as cli
+from tests.testutils.integration import assert_contains
+
+
+pytestmark = pytest.mark.integration
+
+
+DATA_DIR = os.path.join(
+    os.path.dirname(os.path.realpath(__file__)),
+    "project"
+)
+
+
+@pytest.mark.datafiles(DATA_DIR)
+def test_pip_source_import(cli, tmpdir, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    checkout = os.path.join(cli.directory, 'checkout')
+    element_path = os.path.join(project, 'elements')
+    element_name = 'pip/hello.bst'
+
+    element = {
+        'kind': 'import',
+        'sources': [
+            {
+                'kind': 'local',
+                'path': 'files/pip-source'
+            },
+            {
+                'kind': 'pip',
+                'url': 'file://{}'.format(os.path.realpath(os.path.join(project, 'files', 'pypi-repo'))),
+                'requirements-files': ['myreqs.txt'],
+                'packages': ['app2']
+            }
+        ]
+    }
+    os.makedirs(os.path.dirname(os.path.join(element_path, element_name)), exist_ok=True)
+    _yaml.dump(element, os.path.join(element_path, element_name))
+
+    result = cli.run(project=project, args=['track', element_name])
+    assert result.exit_code == 0
+
+    result = cli.run(project=project, args=['build', element_name])
+    assert result.exit_code == 0
+
+    result = cli.run(project=project, args=['checkout', element_name, checkout])
+    assert result.exit_code == 0
+
+    assert_contains(checkout, ['/.bst_pip_downloads',
+                               '/.bst_pip_downloads/HelloLib-0.1.tar.gz',
+                               '/.bst_pip_downloads/App2-0.1.tar.gz'])
+
+
+@pytest.mark.datafiles(DATA_DIR)
+def test_pip_source_build(cli, tmpdir, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    element_path = os.path.join(project, 'elements')
+    element_name = 'pip/hello.bst'
+
+    element = {
+        'kind': 'manual',
+        'depends': ['base.bst'],
+        'sources': [
+            {
+                'kind': 'local',
+                'path': 'files/pip-source'
+            },
+            {
+                'kind': 'pip',
+                'url': 'file://{}'.format(os.path.realpath(os.path.join(project, 'files', 'pypi-repo'))),
+                'requirements-files': ['myreqs.txt'],
+                'packages': ['app2']
+            }
+        ],
+        'config': {
+            'install-commands': [
+                'pip3 install --no-index --prefix %{install-root}/usr .bst_pip_downloads/*.tar.gz',
+                'chmod +x app1.py',
+                'install app1.py  %{install-root}/usr/bin/'
+            ]
+        }
+    }
+    os.makedirs(os.path.dirname(os.path.join(element_path, element_name)), exist_ok=True)
+    _yaml.dump(element, os.path.join(element_path, element_name))
+
+    result = cli.run(project=project, args=['track', element_name])
+    assert result.exit_code == 0
+
+    result = cli.run(project=project, args=['build', element_name])
+    assert result.exit_code == 0
+
+    result = cli.run(project=project, args=['shell', element_name, '/usr/bin/app1.py'])
+    assert result.exit_code == 0
+    assert result.output == """Hello App1!
+"""
diff --git a/tests/integration/project/files/pip-source/app1.py b/tests/integration/project/files/pip-source/app1.py
new file mode 100644
index 000000000..ab1005ba4
--- /dev/null
+++ b/tests/integration/project/files/pip-source/app1.py
@@ -0,0 +1,11 @@
+#!/usr/bin/env python3
+
+from hellolib import hello
+
+
+def main():
+    hello('App1')
+
+
+if __name__ == '__main__':
+    main()
diff --git a/tests/integration/project/files/pip-source/myreqs.txt b/tests/integration/project/files/pip-source/myreqs.txt
new file mode 100644
index 000000000..c805aae53
--- /dev/null
+++ b/tests/integration/project/files/pip-source/myreqs.txt
@@ -0,0 +1 @@
+hellolib
diff --git a/tests/integration/project/files/pypi-repo/app2/App2-0.1.tar.gz b/tests/integration/project/files/pypi-repo/app2/App2-0.1.tar.gz
new file mode 100644
index 000000000..86cb43cfe
--- /dev/null
+++ b/tests/integration/project/files/pypi-repo/app2/App2-0.1.tar.gz
diff --git a/tests/integration/project/files/pypi-repo/app2/index.html b/tests/integration/project/files/pypi-repo/app2/index.html
new file mode 100644
index 000000000..5bc72e47c
--- /dev/null
+++ b/tests/integration/project/files/pypi-repo/app2/index.html
@@ -0,0 +1,8 @@
+<html>
+  <head>
+    <title>Links for app1</title>
+  </head>
+  <body>
+    <a href='App2-0.1.tar.gz'>App2-0.1.tar.gz</a><br />
+  </body>
+</html>
diff --git a/tests/integration/project/files/pypi-repo/hellolib/HelloLib-0.1.tar.gz b/tests/integration/project/files/pypi-repo/hellolib/HelloLib-0.1.tar.gz
new file mode 100644
index 000000000..3b0884c66
--- /dev/null
+++ b/tests/integration/project/files/pypi-repo/hellolib/HelloLib-0.1.tar.gz
diff --git a/tests/integration/project/files/pypi-repo/hellolib/index.html b/tests/integration/project/files/pypi-repo/hellolib/index.html
new file mode 100644
index 000000000..eb9935c7f
--- /dev/null
+++ b/tests/integration/project/files/pypi-repo/hellolib/index.html
@@ -0,0 +1,8 @@
+<html>
+  <head>
+    <title>Links for app1</title>
+  </head>
+  <body>
+    <a href='HelloLib-0.1.tar.gz'>HelloLib-0.1.tar.gz</a><br />
+  </body>
+</html>
diff --git a/tests/sources/pip.py b/tests/sources/pip.py
new file mode 100644
index 000000000..8b4c213dc
--- /dev/null
+++ b/tests/sources/pip.py
@@ -0,0 +1,47 @@
+import os
+import pytest
+
+from buildstream._exceptions import ErrorDomain
+from buildstream import _yaml
+from tests.testutils import cli
+
+DATA_DIR = os.path.join(
+    os.path.dirname(os.path.realpath(__file__)),
+    'pip',
+)
+
+
+def generate_project(project_dir, tmpdir):
+    project_file = os.path.join(project_dir, "project.conf")
+    _yaml.dump({'name': 'foo'}, project_file)
+
+
+# Test that without ref, consistency is set appropriately.
+@pytest.mark.datafiles(os.path.join(DATA_DIR, 'no-ref'))
+def test_no_ref(cli, tmpdir, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    generate_project(project, tmpdir)
+    assert cli.get_element_state(project, 'target.bst') == 'no reference'
+
+
+# Test that pip is not allowed to be the first source
+@pytest.mark.datafiles(os.path.join(DATA_DIR, 'first-source-pip'))
+def test_first_source(cli, tmpdir, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    generate_project(project, tmpdir)
+    result = cli.run(project=project, args=[
+        'show', 'target.bst'
+    ])
+    result.assert_main_error(ErrorDomain.ELEMENT, None)
+
+
+# Test that error is raised when neither packges nor requirements files
+# have been specified
+@pytest.mark.datafiles(os.path.join(DATA_DIR, 'no-packages'))
+def test_no_packages(cli, tmpdir, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    generate_project(project, tmpdir)
+    result = cli.run(project=project, args=[
+        'show', 'target.bst'
+    ])
+    result.assert_main_error(ErrorDomain.SOURCE, None)
diff --git a/tests/sources/pip/first-source-pip/target.bst b/tests/sources/pip/first-source-pip/target.bst
new file mode 100644
index 000000000..e5f20ab0b
--- /dev/null
+++ b/tests/sources/pip/first-source-pip/target.bst
@@ -0,0 +1,6 @@
+kind: import
+description: pip should not be allowed to be the first source
+sources:
+- kind: pip
+  packages:
+  - flake8
diff --git a/tests/sources/pip/no-packages/file b/tests/sources/pip/no-packages/file
new file mode 100644
index 000000000..980a0d5f1
--- /dev/null
+++ b/tests/sources/pip/no-packages/file
@@ -0,0 +1 @@
+Hello World!
diff --git a/tests/sources/pip/no-packages/target.bst b/tests/sources/pip/no-packages/target.bst
new file mode 100644
index 000000000..0d8b948c4
--- /dev/null
+++ b/tests/sources/pip/no-packages/target.bst
@@ -0,0 +1,6 @@
+kind: import
+description: The kind of this element is irrelevant.
+sources:
+- kind: local
+  path: file
+- kind: pip
diff --git a/tests/sources/pip/no-ref/file b/tests/sources/pip/no-ref/file
new file mode 100644
index 000000000..980a0d5f1
--- /dev/null
+++ b/tests/sources/pip/no-ref/file
@@ -0,0 +1 @@
+Hello World!
diff --git a/tests/sources/pip/no-ref/target.bst b/tests/sources/pip/no-ref/target.bst
new file mode 100644
index 000000000..ec450b7ef
--- /dev/null
+++ b/tests/sources/pip/no-ref/target.bst
@@ -0,0 +1,8 @@
+kind: import
+description: The kind of this element is irrelevant.
+sources:
+- kind: local
+  path: file
+- kind: pip
+  packages:
+  - flake8