vyperimports.txt

How do Vyper imports work?

*must* start at the beginning of a line
must stay within a single line... however note that a backslash before a newline
causes the line to continue!  [The newline is then treated as whitespace.]

no, backslashes do not allow you to interject a comment :P

syntax:

import path as alias
from path1 import path2
from path1 import path2 as alias

Paths use dots as separators (though see below); slashes are not allowed.
path2 may not contain dots.
path1 may contain leading dots (discussed below).

NOTE: THERE MAY BE WHITESPACE BEFORE AND AFTER DOTS!

Bult-in interfaces:
from vyper.interfaces import ERC20
from vyper.interfaces import ERC721
[currently; may be more in future, but may assume they'll all be in
vyper.interfaces]

Path processing:

Dots, other than at the beginning of path1, are converted to slashes.
Dots are not allowed in path2.
A slash is inserted between path1 and path2.
If there are n dots at the beginning of path1, they are treated as follows:
0: ""
1: "./"
n>1: "../", n-1 times

Path resolution:
In the JSON case, interfaces is checked before sources.
But if there's ambiguity at that point, it'll fail!
So we should try .json before .vy for our purposes.

Order to try files:
./path.json
project_root/path.json [skipped if path is explicitly relative]
./path.vy
project_root/path.vy   [skipped if path is explicitly relative]

In non-JSON mode, project root is working directory if not explicitly set with
-p option.
In JSON mode, project root is "/", but we'll ignore this and just let FS
handle things by treating absolute things as relative to the contracts
directory.