Why no extension when I save new file?

[YoyYoy]

When I set language (in the bottom right corner, e.g. HTML) and then save file, it’s saved with no extension…
Why?
There is .html extension, right?

[kingkeith]

this behavior is explored in more detail here:

Build 3103 Creating new files assumed file extension can not be changed

It might be specific to only some versions of MacOS perhaps? I just ran a quick test across my Windows 7 machine, my Linux Slackware machine and my MacBook running 10.10.5, all running build 3157. In the test I had a window split into two groups, with an unsaved plain text file on the left and an unsaved JavaScript file on the right. I ran two tests; what happens if you enter the filename test, and what happens if you enter the filename test.ext. I ended up with this table (please excuse the…