Release post for v3.4.1

docs/_posts/2017-03-02-jekyll-3-4-1-released.markdown

@@ -0,0 +1,106 @@
+---
+title: 'Jekyll 3.4.1, or "Unintended Consequences"'
+date: 2017-03-02 14:20:26 -0500
+author: parkr
+version: 3.4.1
+categories: [release]
+---
+
+Conformity is a confounding thing.
+
+We write tests to ensure that a piece of functionality that works today
+will work tomorrow, as further modifications are made to the codebase. This
+is a principle of modern software development: every change must have a
+test to guard against regressions to the functionality implemented by that
+change.
+
+And yet, occasionally, our very best efforts to test functionality will be
+thwarted. This is because of how our code produces unintended
+functionality, which naturally goes untested.
+
+In our documentation, we tell users to name their posts with the following
+format:
+
+```text
+YYYY-MM-DD-title.extension
+```
+
+That format specifies exactly four numbers for the year, e.g. 2017, two
+letters for the month, e.g. 03, and two letters for the day, e.g. 02. To
+match this, we had the following regular expression:
+
+```ruby
+%r!^(?:.+/)*(\d+-\d+-\d+)-(.*)(\.[^.]+)$!
+```
+
+You might already see the punchline. While our documentation specifies the
+exact number of numbers that is required for each section of the date, our
+regular expression does not enforce this precision. What happens if a user
+doesn't conform to our documentation?
+
+We recently [received a bug report](https://github.com/jekyll/jekyll/issues/5603)
+that detailed how the following file was considered a post:
+
+```text
+84093135-42842323-42000001-b890-136270f7e5f1.md
+```
+
+Of course! It matches the above regular expression, but doesn't satisfy
+other requirements about those numbers being a valid date (unless you're
+living in a world that has 43 million months, and 42 million (and one)
+days). So, we [modified the regular expression to match our
+documentation](https://github.com/jekyll/jekyll/pull/5609):
+
+```ruby
+%r!^(?:.+/)*(\d{4}-\d{2}-\d{2})-(.*)(\.[^.]+)$!
+```
+
+Our tests all passed and we were properly excluding this crazy date with 43
+million months and days. This change shipped in Jekyll v3.4.0 and all was
+well.
+
+Well, not so much.
+
+A very common way to specify the month of February is `2`. This is true for
+all single-digit months and days of the month. Notice anything about our
+first regular expression versus our second? The second regular expression
+imposes a **minimum**, as well as maximum, number of digits. This change
+made Jekyll ignore dates with single-digit days and months.
+
+The first eight years of Jekyll's existence had allowed single-digit days
+and months due to an imprecise regular expression. For some people, their
+entire blog was missing, and there were no errors that told them why.
+
+After receiving a few bug reports, it became clear what had happened.
+Unintended functionality of the last eight years had been broken. Thus,
+v3.4.0 was broken for a non-negligible number of sites. With a test site
+in-hand from @andrewbanchich, I tracked it down to this regular expression
+and [reintroduced](https://github.com/jekyll/jekyll/pull/5920) a proper
+minimum number of digits for each segment:
+
+```ruby
+%r!^(?:.+/)*(\d{2,4}-\d{1,2}-\d{1,2})-(.*)(\.[^.]+)$!
+```
+
+And, I wrote a test.
+
+This change was quickly backported to v3.4.0 and here we are: releasing
+v3.4.1. It will fix the problem for all users who were using single-digit
+months and days.
+
+With this, I encourage all of you to look at your code for *unintended*
+functionality and make a judgement call: if it's allowed, *should it be*?
+If it should be allowed, make it *intended* functionality and test it! I
+know I'll be looking at my code with much greater scrutiny going forward,
+looking for unintended consequences.
+
+Many thanks to our Jekyll affinity team captains who helped out, including
+@pathawks, @pnn, and @DirtyF. Thanks, too, to @ashmaroli for reviewing my
+change with an eye for consistency and precision. This was certainly a team
+effort.
+
+We hope Jekyll v3.4.1 brings your variable-digit dates back to their
+previous glory. We certainly won't let that unintended functionality be
+unintended any longer.
+
+As always, Happy Jekylling!