From: jxf+ruby@...
Date: 2014-07-19T08:01:34+00:00
Subject: [ruby-core:63862] [ruby-trunk - Bug #10075] [Open] URI#join seems to violate Principle of Least Surprise

Issue #10075 has been reported by John Feminella.

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Bug #10075: URI#join seems to violate Principle of Least Surprise
https://bugs.ruby-lang.org/issues/10075

* Author: John Feminella
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
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The [documentation](http://www.ruby-doc.org/stdlib-2.1.2/libdoc/uri/rdoc/URI.html#method-c-join) for `URI.join` says:

> "Joins URIs."

Let's look at what a similar `join` method [documentation](http://www.ruby-doc.org/core-2.1.2/File.html#method-c-join) says, on `File`:

> Returns a new string formed by joining the strings using File::SEPARATOR.

That seems pretty clear. Indeed, we get:

~~~
File.join 'path', 'to', 'join'
# => "path/to/join"
~~~

which is what we expected. What do we get if we try the natural `URI` equivalent?

~~~
> URI.join('http://example.com', 'foo', 'bar')
~~~

We probably expect something like:

~~~
# => "http://example.com/foo/bar"
~~~

but we'll actually get

~~~
# => "http://example.com/bar"
~~~

This seems surprising and counterintuitive, even if it matches the documentation behavior, because the documentation doesn't explain why that's the case. I think if Ruby is going to be surprising in that way, it needs to explain that to users in the documentation.



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