Checking overrides when upgrading

Here's a question that came up in the vwnc mailing list. Suppose that you have an application which has overrides of a number of system methods. I'm also going to start referring to overrides as redefines here, because I never liked the ambiguity between an override in a subclass and the replacement of a definition that VisualWorks uses the term for. So I'll try calling them redefines here, even though it makes for a lot of backspacing.

Anyway, let's say that this was built in VisualWorks 7.6, but now you're upgrading to 7.8, and you want to check which of these methods no longer apply. That can be complicated in general, but a basic first check is if the method we were redefining changed between VisualWorks 7.6 and 7.8. That's a bit tedious to check manually, but we can script it.

Of course, this depends on how we've organized things. The original question came up in the context of having grouped redefinitions by the package that contained the thing being redefined. So, if we redefined a method in "Assets", we'd create a package "Assets patches" and put the redefinition there.

So here's an example of a workspace script for finding these. It assumes that we've published the old version of the base into our local database, and that we've loaded our code into a new image.

     mySession := StoreLoginFactory currentStoreSession.
     versionToUpgradeFrom := '7.7 '.
     patchPackages := Store.Registry allPackages select: [:each |
          each name like: '% patches'].

So, first we need to get a StoreGlorp session which we'll use to do our queries, and we define a variable for how we'll find the old versions. We'll also need the list of patch packages that we have in the image. I used the #like: method to do the matching, which does it in SQL style, rather than the more traditional matches:, or even regular expressions, but they'd all work.

     patchPackages do: [:eachPatchPackage | 
         basePackageName := eachPatchPackage name readStream upTo: Character space.
         currentOverriddenPackage := Store.Registry packageNamed: basePackageName.
   
Now we start a loop over each of our patch packages. The first thing we need to know is what the basic package is, which we do based on the simple naming convention described above.

              baseQuery := Query readOneOf: StorePackage where: [:each | 
                  (each name = basePackageName & 
                          (each version like: '%', versionToUpgradeFrom, '%')].
              baseQuery orderBy: [:each | each timestamp descending].
              baseVersion := mySession execute: baseQuery.

Now we do a query to find the appropriate old version. So this involves a Glorp query to find packages by that name, whose version string matches the variable we set at the beginning. If there are multiples, we take only the latest, by sorting them in descending order and just taking the first one. I'm dealing with the Cincom internal repository, so there will be lots and lots of versions of base code. In a project repository there are probably only a few, making it fairly simple to find this.

Once we've done that, we'll loop over the methods in the patch package, and get the three different versions of the method: ours, the new base image version, and the old base image version. These will be three different kinds of objects, and the APIs for manipulating them and getting them are, well, let's just say not as polymorphic as they might be. Our method will be a CompiledMethod. The new version in the image will be an OverriddenMethod. And the one we read from the database will be a StoreMethodInPackage, mapped to the database. Getting that one is a bit fussy, in that we need to make sure we're asking for the class by name, and the name should be exactly the way it will be in the database.

         eachPatchPackage methods do: [:eachMethodDescription |
                  imageMethod := eachMethodDescription method.
                 oldOverridden := baseVersion 
                       method: imageMethod selector 
                       forClassNamed: imageMethod mclass instanceBehavior
                      absoluteName meta: imageMethod mclass isMeta.
                 newOverridden := Override 
                       selector: imageMethod selector 
                       class: imageMethod mclass 
                       in: currentOverriddenPackage.

Finally, we get the source code for the old and the new versions and check them. If the new base version doesn't exist, then that method was either deleted or moved to another package, and we definitely need to think about our redefinition. And if the source code is different, we also want to think about it. Then there's the question of what to do if there's something to think about. We could easily write that to the file or to the Transcript, but in this case what I've done is open a simple text comparison window on the two. That could get ugly if there are a large number, but is nice to work with for just a few.

                  (newOverridden isNil 
                       or: [oldOverridden sourceCode ~= newOverridden sourceCode]) 
                  ifTrue: [
                         | view |
                         view := SideBySideTextComparisonView new 
                               leftText: oldOverridden sourceCode 
                               rightText: newOverridden sourceCode.
                         ScheduledWindow new component: view; openWithExtent: 800@600]]].

This would need to be tweaked for particular environments, but seems like it might be a good start towards making that sort of migration a bit easier. And if I can figure out how to get the syntax highlighting on this blog working, it might get prettier to read here.

Looking at the public repository easily

A quick note. Today someone was wishing there was a way to see what was in the public repository easily without having to fire up Smalltalk. And there is. There's an index of it that's google searchable. It's fairly rough, and it omits things that it thinks aren't interesting, including packages without comments. But it's still quite useful.

Fun with Mail (part 1)

A description of switching around with email clients, and writing some IMAP code in Smalltalk.

I've been a Eudora user for many years. I started using it back when I was a student, and mostly stuck with it, with a bit of time off using VM in Emacs as my primary client. I never liked Outlook, but was able to so I just kept using Eudora in preference to that for corporate email. One of the very nice things in the later versions of Eudora was the search system. The UI was slightly awkward, but it was fast and gave good results. And I keep a lot of email, so that's important to me. I'm at about 5GB right now, with some of it going as far back as 1990.

Unfortunately, Eudora has been abandonware for quite a while now. I resisted switching for a long time, but there were starting to be enough problems that it had to happen.

I wasn't sure what client I'd end up with. The various webmail solutions seemed to be out because none of them seemed to have ways for me to upload huge archives of old mail. So I figured I'd end up with an actual mail client on my machine. In order to be able to try out different ones, and also because I thought it'd be fun, I set up a small Linux server with IMAP (using dovecot) and had it fetch the messages from my various accounts to one location.

Getting the email over was a bit of an adventure. It was possible, in Eudora, to set up an account on the IMAP server, and then to drag folders over onto it, copying their contents. But that was very slow, and tended to crash. Eventually I found a Mac called Eudora Mailbox Cleaner that can also convert the format, and I was able to use that to import both my old Eudora mail, and some other stuff that wasn't in Eudora, but was saved in more or less Unix mailbox format. It crashed a couple of times part-way through, but with a bit of babysitting I got it all converted into local folders in Thunderbird. Thunderbird would let you move stuff from local folders into IMAP as well, and it wasn't quite as slow and didn't crash quite as often.

So ultimately I had my mail converted, and was able to try out some clients. Apple's mail was the main other one I tried, but it missing features I wanted, so I ended up mostly using Thunderbird, particularly with the QuickFolders and Archive This extensions, which were helpful for quick filing and finding folders. But Thunderbird had some problems. The search was not particularly fast, at least not on the kind of volume of mail that I had. Worse, the filters didn't seem to work reliably. I don't know if that was just an issue with Thunderbird and IMAP, but the spam filtering wasn't moving things out of the Inbox reliably, and mailing list messages weren't reliably going into the right folders.

I decided to take this as an opportunity to write some Smalltalk code, and made myself a little cron job that would run a Smalltalk program to filter the messages. Along the way, I learned a bit about IMAP and the VisualWorks libraries for using them. So in part 2, I'll talk about some of the code that I ended up with.

New blog address

Hello World,
   I'm Alan Knight, the engineering manager for Cincom Smalltalk and principal developer of the GLORP object-relational mapping framework for Smalltalk. I did have a blog on the Cincom Smalltalk site for a while, which I posted to, um, occasionally, but without Jim Robertson around to maintain that infrastructure I've decided to use a more conventional service. And since Blogger seems to have at least the potential for automatic Smalltalk syntax highlighting that seemed like as good a reason as any to choose it.

  Once, many years ago, when I was a columnist for The Smalltalk Report someone asked me at a conference if I was "the" Alan Knight. And I really wasn't sure if I was or not. But now I know - I'm not "the" Alan Knight, but rather this is - LEGEND! I, on the other hand, am just a computer guy, live in Ottawa, play and referee soccer, and am married to Kirsten Carlson, a flute player and teacher.

  Before I worked at Cincom I was with The Object People, a training and consulting company in Ottawa, Canada. They ended up best known for developing TOPLink first in Smalltalk and then in Java, and for a while I was the chief architect. TOPLink eventually ended up owned by Oracle, but TOPLink/Smalltalk is still interesting as an early example of O/R mapping software that is clearly prior art to any number of patents. For that matter, so is the ObjectLens software (which patent lawyers seem to mostly know by its very early and short-lived name of Infobase) that my employer Cincom inherited from ObjectShare/ParcPlace-Digitalk/Parcplace and still sell today.

  In this space I hope to blog about Smalltalk and programming in general, Cincom Smalltalk in particular, Glorp and other O/R mapping issues, and anything else that seems interesting enough to post. And hopefully post things with more actual content and not quite so many links. Wish me luck.