WIP: Implement HTTP

[pjbull]

Initial pass at http.

• implemented with standard library
• tested against Python http.server
• will try writing/deleting files with PUT/DELETE in case your server allows it
• will try parsing "directories" from the returned HTML; seems like this grabs the right things from python's http.server and also looks like it should work for apache and nginx file servers from my googling. (allows user to override this method for their own server)
• Bonus fix, use .anchor instead of .cloud_prefix where appropriate. For cloud providers, .anchor is the same as .cloud_prefix (e.g., s3://). For http, the anchor should be the server http://example.com and the .cloud_prefix should be http://. Constructing new paths should use .anchor

Limitations/caveats:

• Assumes that url must have suffix (e.g., http://example.com/file.txt) to be a file; if no suffix, assumes dir. This is definitely not true of real-world URLs, but maybe is an ok assumption for anything serving files?

Left to do:

• Add https
• Expose all the parsed url components publicly (not behind HttpPath._url).
• Update default file + dir function to be based on a trailing slash
• Allow also overriding the file vs. dir function
• Add tests for http specific functions
• Turn off noisy logs for test http server by default
• Add tests that url search strings and fragments are persisted correctly
• Documentation (table, caveats, docstrings, headers, auth, files v dirs, etc.)
• HTTP Test suite often passes locally, but not always; need to debug and make less flaky

Closes #455

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[jayqi]

Bonus fix, use .anchor instead of .cloud_prefix where appropriate. For cloud providers, .anchor is the same as .cloud_prefix (e.g., s3://). For http, the anchor should be the server http://example.com and the .cloud_prefix should be http://. Constructing new paths should use .anchor

We shouldn't call this "anchor". Anchor has a different meaning in a close enough context that I think this will be confusing. In particular, "anchor" colloquially refers to "anchor tags" in HTML documents, which you can reference within a URL with fragment identifiers #someref. The part preceding the :// is called "scheme" in URL/URI vocabulary and we should probably stick with that if we're going to call it anything. (Reference)

Assumes that url must have suffix (e.g., http://example.com/file.txt) to be a file; if no suffix, assumes dir. This is definitely not true of real-world URLs, but maybe is an ok assumption for anything serving files?

I'm not sure I like this. There are often genuine files that don't have file extensions that are usually plain text files, e.g., README, LICENSE, Makefile.

My impression is that, (while it's not absolute) the most common convention and default for many web servers and frameworks is to use a trailing slash explicitly to serve directories.

[pjbull]

We shouldn't call this "anchor". Anchor has a different meaning in a close enough context that I think this will be confusing.

Hm, yeah, I can see this is potentially confusing, but we're not calling it "anchor" arbitrarily. We're looking for the right analogy to populate the existing .anchor pathlib property. In the pathlib context .anchor is a Path object that is drive + root. We're using it to refer to scheme + netloc (not just the scheme) which reasoning by analogy feels about right. The difference from the cloud providers is that the scheme is the root is the drive (e.g., listing s3:// lists buckets you have access to). IMO docs can cover this source of potential confusion without too much worry, especially since anything referring to an anchor in a url is most often called the "fragment".

use a trailing slash explicitly to serve directories.

Yeah, this was the other default rule I considered—I think you're right it's probably a more reliable default. That is how the python server works (except for the root, which does not redirect to the slash). Also planning for the method to be overridable so people can configure for their particular servers if it is different.