From 74fc4685c016b0bb2694307d1d2a496fce4a6479 Mon Sep 17 00:00:00 2001
From: Nick Coghlan <ncoghlan@gmail.com>
Date: Nov 21 2017 06:43:53 +0000
Subject: Issue #52: Handle missing metadata


Adds a new "MissingMetadata" exception to the
metadata loader, and special cases that in the
CLI machinery.

Also adds a new test file for end-to-end CLI test
cases that test the full CLI invocation, not just
the internal Python API.

---

diff --git a/src/_fedmod/__main__.py b/src/_fedmod/__main__.py
index 9e88f92..0f7eab1 100644
--- a/src/_fedmod/__main__.py
+++ b/src/_fedmod/__main__.py
@@ -1,9 +1,8 @@
 #!/usr/bin/env python3
 
 import sys
-from .cli import ModtoolsCLIHelper
+from . import cli
 
 
 if __name__ == "__main__":
-    cli = ModtoolsCLIHelper()
     sys.exit(cli.run())
diff --git a/src/_fedmod/_repodata.py b/src/_fedmod/_repodata.py
index 7f632b3..f5bd8d8 100644
--- a/src/_fedmod/_repodata.py
+++ b/src/_fedmod/_repodata.py
@@ -28,6 +28,9 @@ _F27_MAIN_REPO = "https://dl.fedoraproject.org/pub/fedora/linux/development/27/E
 _F27_UPDATES_REPO = "https://dl.fedoraproject.org/pub/fedora/linux/updates/27/"
 _F27_BOOTSTRAP_MODULEMD = "https://src.fedoraproject.org/modules/bootstrap/raw/master/f/bootstrap.yaml"
 
+class MissingMetadata(Exception):
+    """Reports failure to find the local metadata cache"""
+
 @attributes
 class RepoPaths:
     remote_repo_url = attrib(str)
@@ -167,11 +170,20 @@ def _populate_module_reverse_lookup():
         return
     metadata_dir = os.path.join(_x86_64_MODULE_INFO.local_cache_path)
     repomd_fname = os.path.join(metadata_dir, "repodata", "repomd.xml")
+    if not os.path.exists(repomd_fname):
+        msg = f"{repomd_fname!r} does not exist. Run `fedmod fetch-metadata`."
+        raise MissingMetadata(msg)
     repomd_xml = etree.parse(repomd_fname)
     repo_relative_modulemd = _read_repomd_location(repomd_xml, "modules")
     if repo_relative_modulemd is None:
-        raise RuntimeError(f"No 'modules' entry found in {repomd_fname}. Is the metadata for a non-modular repo?")
+        msg = (f"No 'modules' entry found in {repomd_fname!r}. "
+                "Is the metadata for a non-modular repo?")
+        raise MissingMetadata(msg)
     repo_modulemd_fname = os.path.join(metadata_dir, repo_relative_modulemd)
+    if not os.path.exists(repo_modulemd_fname):
+        msg = (f"{repo_modulemd_fname!r} does not exist. "
+                "Try running `fedmod fetch-metadata` again.")
+        raise MissingMetadata(msg)
     with gzip.open(repo_modulemd_fname, "r") as modules_yaml_gz:
         modules_yaml = modules_yaml_gz.read()
     modules = modulemd.loads_all(modules_yaml)
@@ -195,6 +207,10 @@ def _populate_module_reverse_lookup():
                 _BETTER_RPM_REVERSE_LOOKUP[rpmprefix] = []
             _BETTER_RPM_REVERSE_LOOKUP[rpmprefix].append(module.name)
     # Read the extra RPM bootstrap metadata
+    if not os.path.exists(_BOOTSTRAP_REVERSE_LOOKUP_CACHE):
+        msg = (f"{_BOOTSTRAP_REVERSE_LOOKUP_CACHE!r} does not exist. "
+                "Try running `fedmod fetch-metadata` again.")
+        raise MissingMetadata(msg)
     with open(_BOOTSTRAP_REVERSE_LOOKUP_CACHE, "r") as cachefile:
         _BOOTSTRAP_REVERSE_LOOKUP.update(json.load(cachefile))
 
diff --git a/src/_fedmod/cli.py b/src/_fedmod/cli.py
index 59f3cea..cb099b9 100644
--- a/src/_fedmod/cli.py
+++ b/src/_fedmod/cli.py
@@ -176,6 +176,9 @@ def run():
 
     except KeyboardInterrupt:
         print('\nInterrupted by user')
+    except _repodata.MissingMetadata as e:
+        print(e, file=sys.stderr)
+        sys.exit(2)
     except Exception as e:
         logging.exception("Unexpected exception")
         sys.exit(1)
diff --git a/tests/test_cli_ux.py b/tests/test_cli_ux.py
new file mode 100644
index 0000000..707a6f4
--- /dev/null
+++ b/tests/test_cli_ux.py
@@ -0,0 +1,33 @@
+"""End-to-end subprocess based testing for the CLI behaviour"""
+
+import pytest
+import os
+import re
+import sys
+import subprocess
+
+from _fedmod._repodata import CACHEDIR
+
+def _run_fedmod(args):
+    # Run via the -m switch to ensure we get the expected version of fedmod
+    cmd = [sys.executable, "-m", "_fedmod"]
+    cmd.extend(args)
+    return subprocess.run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+
+class TestMissingMetadata(object):
+
+    def setup(self):
+        self._moved_cache_dir = _moved_cache_dir = CACHEDIR + "__"
+        os.rename(CACHEDIR, _moved_cache_dir)
+
+    def teardown(self):
+        os.rename(self._moved_cache_dir, CACHEDIR)
+
+    def test_missing_metadata_handling(self, capfd):
+        result = _run_fedmod(["list-modules"])
+        assert result.returncode == 2
+        assert result.stdout == b""
+        expected_err_msg = b"'<filename>' does not exist. Run `fedmod fetch-metadata`.\n"
+        err_msg = re.sub(b"'.*'", b"'<filename>'", result.stderr)
+        assert err_msg == expected_err_msg
+