Error Dialog for Invalid Filenames is Incomplete

[chipbuster]

Description

When an invalid sketch name is detected, the resulting error dialog does not include all requirements for filenames. This can result in a filename which appears to follow all the rules being rejected.

Possibly related to #741, but skimming that issue, it looked like that was intended to be about compiler errors, while this is more related to IDE errors.

Expected Behavior

If the filename does not follow all the rules, the error dialog should specify what to change.

Current Behavior

The error dialog says:

<filename> is not a valid name for sketch code.
Better to stick to ASCII, no spaces, and make sure
it doesn't start with a number.

However, this does not address the following cases:

1. When a non-alphanumeric ASCII character is included in the filename.
2. When the stem of the filename is longer than 63 characters.

Steps to Reproduce

Create a file named hello-world.pde or a file whose name consists of the letter 'a' 64 times followed by .pde.

Your Environment

• Processing version: 4.2
• Operating System and OS version: Arch Linux
• Other information: I am (mostly) not manually creating filenames which violate these rules. Rather, it's happening because my learning management system (Canvas) likes to rename files on its own whim, and it tends to add these sorts of things.

Possible Causes / Solutions

One solution would be to explicitly name all the requirements for a filename, e.g. the message reads something like

<filename> is not a valid name for a sketch. Your files must:

1. Use only ASCII letters and numbers.
2. Start with a letter.
3. Be shorter than 63 characters.

but this is not complete either (e.g. right now you are allowed to have underscores in the name).