app.py

# vim: et sw=4 sts=4

from flask import Flask, escape, redirect
app = Flask(__name__)

import posixpath
import requests
from sphinx.util.inventory import InventoryFile
from werkzeug.contrib.iterio import IterIO

INVENTORIES = {
    '3': [
        ('https://docs.python.org/3/', 'https://docs.python.org/3/objects.inv'),
    ],
    '2': [
        ('https://docs.python.org/2/', 'https://docs.python.org/2/objects.inv'),
    ],
}

m = {}

for mapping, l in INVENTORIES.items():
    d = {}
    for uri, inv in l:
        print(f"Getting a {inv!r}")
        r = requests.get(inv, stream=True)
        s = IterIO(r.iter_content())
        inv = InventoryFile.load(s, uri, posixpath.join)
        # medium hack: prefer classes and then functions and then other stuff.
        # when shadowing happens (e.g. 'dict', 'len') this seems to be the order we want
        types = list(inv.keys())
        types.remove('py:class')
        types.remove('py:function')
        types = ['py:class', 'py:function'] + types
        for typ in types:
            entries = inv[typ]
            x = {k.casefold(): v for k, v in entries.items()}
            x.update(d)
            d = x
        # this is another loop so shortened names don't ever take priority over full ones
        for typ in types:
            entries = inv[typ]
            x = {k.split('.')[-1].casefold(): v for k, v in entries.items()}
            x.update(d)
            d = x
    m[mapping] = d

@app.route("/<string:mapping>/<string:obj_id>")
def bounce(mapping, obj_id):
    try:
        index = m[mapping]
    except KeyError:
        return f"I don't know about {escape(mapping)}.", 404
    try:
        projname, version, location, _ = index[obj_id.casefold()]
    except KeyError:
        return f"I don't know about {escape(obj_id)} in {escape(mapping)}", 404
    return redirect(location), 307