Fix spack versions behavior when no URL (#8967)

* Fix spack versions behavior when no URL
* Unit test packages without URLs or safe versions

lib/spack/spack/cmd/versions.py

@@ -42,20 +42,27 @@ def setup_parser(subparser):
 def versions(parser, args):
     pkg = spack.repo.get(args.package)
 
+    tty.msg('Safe versions (already checksummed):')
+
     safe_versions = pkg.versions
+
+    if not safe_versions:
+        print('  Found no versions for {0}'.format(pkg.name))
+        tty.debug('Manually add versions to the package.')
+    else:
+        colify(sorted(safe_versions, reverse=True), indent=2)
+
+    tty.msg('Remote versions (not yet checksummed):')
+
     fetched_versions = pkg.fetch_remote_versions()
     remote_versions = set(fetched_versions).difference(safe_versions)
 
-    tty.msg("Safe versions (already checksummed):")
-    colify(sorted(safe_versions, reverse=True), indent=2)
-
-    tty.msg("Remote versions (not yet checksummed):")
     if not remote_versions:
         if not fetched_versions:
-            print("  Found no versions for %s" % pkg.name)
-            tty.debug("Check the list_url and list_depth attribute on the "
-                      "package to help Spack find versions.")
+            print('  Found no versions for {0}'.format(pkg.name))
+            tty.debug('Check the list_url and list_depth attributes of the '
+                      'package to help Spack find versions.')
         else:
-            print("  Found no unchecksummed versions for %s" % pkg.name)
+            print('  Found no unchecksummed versions for {0}'.format(pkg.name))
     else:
         colify(sorted(remote_versions, reverse=True), indent=2)

lib/spack/spack/package.py

@@ -2063,8 +2063,15 @@ def format_doc(self, **kwargs):
 
     @property
     def all_urls(self):
+        """A list of all URLs in a package.
+
+        Check both class-level and version-specific URLs.
+
+        Returns:
+            list: a list of URLs
+        """
         urls = []
-        if self.url:
+        if hasattr(self, 'url') and self.url:
             urls.append(self.url)
 
         for args in self.versions.values():
@@ -2073,10 +2080,15 @@ def all_urls(self):
         return urls
 
     def fetch_remote_versions(self):
-        """Try to find remote versions of this package using the
-           list_url and any other URLs described in the package file."""
+        """Find remote versions of this package.
+
+        Uses ``list_url`` and any other URLs listed in the package file.
+
+        Returns:
+            dict: a dictionary mapping versions to URLs
+        """
         if not self.all_urls:
-            raise spack.util.web.VersionFetchError(self.__class__)
+            return {}
 
         try:
             return spack.util.web.find_versions_of_archive(

lib/spack/spack/test/cmd/versions.py

@@ -48,3 +48,17 @@ def test_no_unchecksummed_versions():
     """Test a package for which no unchecksummed versions are available."""
 
     versions('bzip2')
+
+
+@pytest.mark.network
+def test_versions_no_url():
+    """Test a package with versions but without a ``url`` attribute."""
+
+    versions('graphviz')
+
+
+@pytest.mark.network
+def test_no_versions_no_url():
+    """Test a package without versions or a ``url`` attribute."""
+
+    versions('opengl')