Improve package version constraint suggestions.

app/models/package_version.py

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 import copy
 import json
 import tarfile
 
 from google.appengine.api import memcache
 from google.appengine.ext import db
@@ skipping 226 matching lines @@
 
         return map(self._import_for_library, self.libraries)
 
     def _import_for_library(self, library):
         """Return the import information for a library in this package."""
         return {'package': self.package.name, 'library': library}
 
     @property
     def example_version_constraint(self):
         """Return the example version constraint for this package."""
-        if self.version.in_initial_development:
-            return json.dumps(">=%s <%d.%d.0" %
-                (self.version, self.version.major, self.version.minor + 1))
-        return json.dumps(
-            ">=%s <%d.0.0" % (self.version, self.version.major + 1))
+        if not self.verison.is_prerelease:
+            return json.dumps("^%s" % self.version)
+
+        return json.dumps(">=%s <%d.%d.%d" % (
+            self.version,
+            self.version.major,
+            self.version.minor,
+            self.version.patch
+        ))

[kustermann, 2015/05/19 08:24:36]

I'm not sure if this is working as intended.

A while ago I filed http://dartbug.com/20404 which was marked as AsDesigned and
says basically:
  "0.0.3-dev" does not satisfy the constraint '>=0.0.3-dev <0.0.3'

=> Your change builds exactly such a constraint.


Now since pub defines it's *own semantics* of what constraints and the operators
<, <=, >, >= mean, and I'm not a pub expert, I don't know what to use. This
issue http://dartbug.com/20302 says:

  "<1.2.3"   No pre-release versions are considered
  "<=1.2.3"  Pre-release versions are considered

This might indicate that we could do:
 a)  ">=1.2.3-dev <=1.2.3"
 b)  ">=1.2.3-dev <=1.2.3-dev"

If option a) is not desired, because we don't want to include 1.2.3, then option
b) seems to be the only choice.


But you're much more familiar with pub's semantic versioning, so maybe I'm
misunderstanding something here?

 
     @property
     def storage_path(self):
         """The Cloud Storage path for this package."""
         # Use the canonical version for the cloud storage path for
         # backwards-compatibility with package versions that were uploaded
         # prior to storing non-canonicalized versions.
         return 'packages/%s-%s.tar.gz' % \
             (self.package.name, self.version.canonical)
 
@@ skipping 49 matching lines @@
 
         if full:
             value.update({
                 'created': self.created.isoformat(),
                 'downloads': self.downloads,
                 'libraries': self.libraries,
                 'uploader': self.uploaderEmail
             })
 
         return value