ivy:retrieve Ant tasks should have overwriteMode of "always" by default, inform
user when file not overwritten
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Key: IVY-1316
URL: https://issues.apache.org/jira/browse/IVY-1316
Project: Ivy
Issue Type: Improvement
Components: Ant
Affects Versions: 2.2.0
Reporter: Brett Langston
The Ant ivy:retrieve task defaults to overwriting the destination file only if
one with a more recent timestamp is available (overwriteMode="newer").
Moreover, if it decides not to overwrite, it informs the user that the artifact
was retrieved, even though it wasn't. This default behavior and incorrect
retrieval message caused us a bit of pain today.
These are the two main problems, with some possible solutions:
1) Even though the ivy.xml file specified the desired revision, it was not
retreived because the desired revision had an older timestamp than what the
user already had. This will happen constantly in the scenario where the user
is changing their ivy.xml file to work with an older version of an artifact.
Why is it assumed that the user will only be pulling down newer and newer
artifacts? It is quite common to want artifacts with older timestamps than
what you are working with at the moment. The default value of
overwriteMode="newer" for the ivy:retrieve task is surprising, and goes against
the default behavior of any other file utilities I can think of.
Proposed solution: Make the ivy:retrieve overwriteMode="always" be the
expected default. After all, if I tell Ivy to retrieve something, I expect it
to be retrieved! It makes much more sense to override this behavior only in
the case where the "newer" behavior is wanted, not the other way around.
2) The ivy:retrieve Ant task told us that the higher version had been
retrieved, even though it was not.
Proposed solution: If Ivy is going to decide not to retrieve an artifact due
to the overwriteMode setting, it should inform the user that the desired
version was found, but that it was not used due to the overwriteMode.
Otherwise, the user (rightly) assumes that if Ivy says an artifact was
retrieved, it was, indeed, retrieved.
In summary, we might have shipped the wrong version of an artifact, just
because the ivy:retrieve task didn't give us the version we asked for due to an
older timestamp. It seems like a default overwriteMode of "newer" is very
dangerous (especially since the user isn't informed of the lack of overwrite),
and that a default overwriteMode of "always" is the more expected behavior when
requesting a file to be placed somewhere.
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