<div dir="ltr">On Mon, Nov 21, 2016 at 2:37 PM, Ricardo N Olivieri <span dir="ltr"><<a href="mailto:ricardo.olivieri@us.ibm.com" target="_blank">ricardo.olivieri@us.ibm.com</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><font size="2" face="sans-serif">Thanks Daniel for the response. That's
probably the reason (i.e. metadata changes in the file inode) for the behavior
we are seeing in SwiftPM.</font><br><font size="2" face="sans-serif"><br>The use case for us is as follows: </font><br><br><font size="2" face="sans-serif">We'd like to improve even further the
performance of the IBM Bluemix buildpack for Swift and one way we could
accomplish this is by not recompiling the Packages folder as long as the
content of that folder has not changed. Without getting into too many details
about cloud foundry buildpacks, for the buildpack to reuse the contents
of the Packages folder in future re-deployments of the same application
to the cloud, the buildpack has to copy the Packages folder a different
folder outside the repo's folder and then copy it back again when the developer
redeploys his/her application. This is when we noticed that despite the
contents of the Packages folder had not changed, SwiftPM still recompiled
all of the dependencies under the Packages folder.</font></blockquote><div><br></div><div>Makes sense, thanks!</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br><font size="2" face="sans-serif">Is there an ETA for using content-based
signatures instead? </font></blockquote><div><br></div><div>No, unfortunately.</div><div><br></div><div>If it is important for your use case, I'd be ok with accepting a PR to change swift-build-tool to only look at the time/size information to workaround this in the meantime.</div><div><br></div><div> - Daniel</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br><br><font size="2" face="sans-serif"><br>Regards,<br> Ricardo Olivieri<br> Software Engineer<br> IBM Swift Engineering at IBM Cloud</font><br><br><br><font size="1" color="#5f5f5f" face="sans-serif">From:
</font><font size="1" face="sans-serif">Daniel Dunbar <<a href="mailto:daniel@zuster.org" target="_blank">daniel@zuster.org</a>></font><br><font size="1" color="#5f5f5f" face="sans-serif">To:
</font><font size="1" face="sans-serif">Ricardo N Olivieri/Austin/IBM@IBMUS</font><br><font size="1" color="#5f5f5f" face="sans-serif">Cc:
</font><font size="1" face="sans-serif"><a href="mailto:swift-build-dev@swift.org" target="_blank">swift-build-dev@swift.org</a></font><br><font size="1" color="#5f5f5f" face="sans-serif">Date:
</font><font size="1" face="sans-serif">11/21/2016 03:58 PM</font><br><font size="1" color="#5f5f5f" face="sans-serif">Subject:
</font><font size="1" face="sans-serif">Re: [swift-build-dev]
SwiftPM recompilation - Packages folder</font><br><font size="1" color="#5f5f5f" face="sans-serif">Sent by:
</font><font size="1" face="sans-serif"><a href="mailto:daniel.dunbar@gmail.com" target="_blank">daniel.dunbar@gmail.com</a></font><br><hr noshade><div class="HOEnZb"><div class="h5"><br><br><br><font size="3">swift-build-tool will currently rebuild any file if it
detects a change to the file inode or device -- my guess is that is what
you are seeing here.</font><br><br><font size="3">My intention is to eventually move to using content-based
signatures to determine the rebuild conditions (for tools where we know
that is safe), which would prevent the rebuild in this situation.</font><br><br><font size="3">Is there a particularly reason it is important to you
that this not rebuild?</font><br><br><font size="3"> - Daniel</font><br><br><font size="3">On Mon, Nov 21, 2016 at 1:54 PM, Ricardo N Olivieri via
swift-build-dev <</font><a href="mailto:swift-build-dev@swift.org" target="_blank"><font size="3" color="blue"><u>swift-build-dev@swift.org</u></font></a><font size="3">>
wrote:</font><br><font size="3">Hello all, <br><br><br>I was wondering if someone could shed some light on how SwiftPM determines
if it needs to compile again any of the source code under the Packages
folder. I had thought that the modified timestamp attribute of
any source code files under the Packages folder was the key for determining
if any of the Swift package dependencies should be recompiled. However,
it seems SwiftPM uses additional criteria to make this determination. Here’s
the test we executed: <br><br><br>1) At T0, we executed swift build. As expected all Swift package dependencies
were cloned and compiled along with the application’s code. <br><br><br><br>2) At T1, we executed swift build again and nothing was recompiled,
as expected since no code changes were made. <br><br><br>3) At T2, we made a copy of the Packages folder and place this copy
in a location outside the repo’s directory. We then deleted the Packages
folder from the repo’s directory, and, finally, we copied the
Packages folder back to its original location in the repo’s directory.
<br><br><br>4) At T3, we executed again swift build and noticed that SwiftPM
recompiled each one of the Swift package dependencies in the Packages folder,
even though no code changes were made. We also double checked that the modified
and creation timestamps for the Packages folder and folders and files in
it were not changed. After doing so, we concluded that though copying the
Packages folder back to the application’s repo did keep the original creation
and modified timestamp values of all files and folders, SwiftPM still recompiled
all of the dependencies in the Packages folder. <br><br><br>Does anyone know why we are seeing in SwiftPM the behavior described above?
</font><font size="2" face="sans-serif"><br><br><br>Regards,<br> Ricardo Olivieri</font><font size="3"><br><br><br>______________________________<wbr>_________________<br>swift-build-dev mailing list</font><font size="3" color="blue"><u><br></u></font><a href="mailto:swift-build-dev@swift.org" target="_blank"><font size="3" color="blue"><u>swift-build-dev@swift.org</u></font></a><font size="3" color="blue"><u><br></u></font><a href="https://lists.swift.org/mailman/listinfo/swift-build-dev" target="_blank"><font size="3" color="blue"><u>https://lists.swift.org/<wbr>mailman/listinfo/swift-build-<wbr>dev</u></font></a><font size="3"><br></font><br><br><br><br>
</div></div></blockquote></div><br></div></div>