Programming Is Hard, Let's Go Shopping

This isn't even about libraries, this is about approaching the right problem: if you, for example, allow only strict XML-compliant HTML, you can build an XML parser that ignores namespaces (which is sufficient for simplified HTML; once you accept namespaces and other parts of XML life gets much harder), from scratch if it makes you feel more manly, in a day... you then have solved the problem.

If you want to let users get a little sloppier, that is itself easy to handle. You can even build a crappy HTML5 parser and then generate your own reasonable (HTML4 strict, for example) output: that will probable take a few days, but is mostly just implementing the spec that Hixie spent forever writing. Even if you get the parser wrong (as it is a long and complicated specification), it doesn't matter, as you are regenerating the output entirely clean. Again: you have solved the problem.

In neither of these scenarios were there lessons to learn or scars to gain: you don't spend years learning how you made mistakes and getting a feel for this deep problem... you simply solve it, as you defined the problem correctly. It is amazing what problems you can solve when you first choose the right problem and then take a direct path to the solution.

Given this, the complaint about the approach Jeff took then discussed libraries (which is what Jeff focused on, possibly due to the title of the other article), but honestly the horrifying part was that it also discussed the solution direction that was taken: finding tons of special cases and attempting to filter the input with regular expressions.

Those are simply not the right tool for the problem. Even simplified XML is not a regular language. The definition of an individual tag might be, but you are up against the horror that is an HTML parser: the same ones Hixie spent years reversing the behaviors of to build the aforementioned parser specification.

So, yeah: you can learn a lot from writing your own code, and you may even want to develop things that are core to your business yourself rather than using libraries, but of you are spending a ton of time, accumulating scars in the process, writing code to solve the wrong problem... just, don't, okay? ;P