What are the allowed characters for an extension? about mime-db HOT 6 CLOSED

Whatever the specification says the extension is for that mime type, we will add. There is no specific rule unless the IANA has some kind of restrictions. I hope that helps.

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Thanks

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Basically we don't have any specific rules, as we don't make them :) we simply aggregate the data from the three sources listed at the top of the readme.

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@jdesrosiers
While I didn't find much with a quick skim of rfc's at IETF... did find rfc2045, rfc2046, rfc2047, rfc2048, and rfc4288 (naming requirements). Having the right industry buzz, canonical lexical grammar, names is usually a key for finding information. More skimming/reading is up to you. 😸

If I were to take an educated guess it would probably be US-ASCII 7-bit and extensions to those standards with encoding using special sequences of ASCII characters that may not normally be allowed. So the period does fall within 0-127 decimal but also could be restrictive somewhere else in some other use case. Interoperability is usually what is aimed for between platforms as well as recognition.

Final resort is to try registering it and they'll tell you if it's okay or not.

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Thanks, I did some similar reading before asking the question and came up with nothing as well. I was hoping to get this added to the custom-types.json list. My understanding is that that's the place types can be defined that aren't part of the three sources you pull from. YAML, for example, isn't on any of those lists. Do I understand correctly that JSON Schema could be added in this way as well? In those cases, I figured you might have some rules that you follow about what you accept that isn't registered by some official standards body, which is why I asked here.

Despite application/schema+json being in use for over a decade, I don't think it's likely to be registered with IANA any time soon because we're not affiliated with any standards body, which seems to be a requirement. The schema.json extension has never been in the specification, but it's emerged as a fairly ubiquitous practice. I expect the first step is to get that added to our spec before it could be accepted here.

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As far as the custom-types, in the ideal world we wouldn't need it, but I acknowledge that there are various things that should be included in the database that are not a part of our sources. Really, as I do not desire to be a registry or debate assignments, the only "rule" is that there should be a primary source that links the file extension to the media type. The best source is some kind of specification. I found https://json-schema.org/draft/2020-12/json-schema-core.html#rfc.section.14.1 which I would gather is the spec for it; no file extension is currently listed there, though.

As far as allowed characters, since this is not a registry, and the extension are just strings, it could in theory contain any chars. Now, if those char make sense to consumer of this module, I don't know, haha. Or file systems, etc. I do know that many folks use the extensions in combination with https://nodejs.org/dist/latest-v16.x/docs/api/path.html#path_path_extname_path so I would guess that given a file name foo.schema.json most things will be unable yo figure out the "correct" media type from the name.

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