Mailing-List: contact zsh-workers-help@zsh.org; run by ezmlm Precedence: bulk X-No-Archive: yes List-Id: Zsh Workers List List-Post: List-Help: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on f.primenet.com.au X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.1 X-AuditID: cbfec7f4-f796c6d000001486-4d-576a540a07ab Date: Wed, 22 Jun 2016 10:01:59 +0100 From: Peter Stephenson To: Zsh hackers list Subject: Re: bug: suffix alias and tabcompletion Message-id: <20160622100159.1d82792f@pwslap01u.europe.root.pri> In-reply-to: References: <20160621193918.GA3768@fau.de> Organization: Samsung Cambridge Solution Centre X-Mailer: Claws Mail 3.7.9 (GTK+ 2.22.0; i386-redhat-linux-gnu) MIME-version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrLLMWRmVeSWpSXmKPExsVy+t/xy7pcIVnhBvcXiVscbH7I5MDoserg B6YAxigum5TUnMyy1CJ9uwSujFltX9gLWoUqNn53aWDs4+ti5OCQEDCRWLM1q4uRE8gUk7hw bz1bFyMXh5DAUkaJed/2soMkhARmMEksP8YHkTjHKNG0dxcLROIso8TqbTUgNouAqsTWmR/Y QGw2AUOJqZtmM4LYIgJaEjtOnmQCsYUFDCTOfX4DNpRXwF6if+lVsHpOgWCJludtUDMLJR4e /Q0W5xfQl7j69xMTxHX2EjOvnGGE6BWU+DH5Hlg9M9D8zduaWCFseYnNa94yQ8xRl7hxdzf7 BEbhWUhaZiFpmYWkZQEj8ypG0dTS5ILipPRcQ73ixNzi0rx0veT83E2MkED+soNx8TGrQ4wC HIxKPLwMXZnhQqyJZcWVuYcYJTiYlUR4HwdkhQvxpiRWVqUW5ccXleakFh9ilOZgURLnnbvr fYiQQHpiSWp2ampBahFMlomDU6qBcast37Puvnc/hKRSpxyK3jyLTdCncg7rjCOqj28aT0yK jph0kcHmTuLdBSEVVbI6KcErnQNVAxirS8u2lhVUL32oMKlDZ0nJUaeDGjdWHNGS7t1/IMSi JdblCtMqfU8JtYZlAcfVHDMb6/cazkg9otccsKxqvvfK9c4hypsvfo4zPnv/b9EuJZbijERD Leai4kQAgjG31WACAAA= X-Seq: zsh-workers 38745 On Tue, 21 Jun 2016 13:18:21 -0700 Bart Schaefer wrote: > On Tue, Jun 21, 2016 at 12:39 PM, Michael Gebhard > wrote: > > > > running the following commands and trying to complete the last line > > by pressing tab produces a zsh taking up 100% cpu. > > > > zsh -f > > touch foo.bar > > alias -s bar='echo a &' > > It's not (just) completion; attempting to run the command "foo.bar" > produces a similar infinite loop. The alias has expanded to "echo a & > foo.bar" which then recursively expands "foo.bar" (because after the > "&" it is in command position again) and off we go. The "touch > foo.bar" isn't required. This is different from a normal alias because in that case the original text is completely removed; you can only encounter the (normal or global) alias again while expanding the alias, which we detect, or after, which is a completely different set of input triggering the expansion so there's no recursion. In this case, the argument foo.bar appears again *after* the alias has been expanded fully because the alias is inserted before it. By the time we get to foo.bar again as the argument, the trace of alias expansion has been removed --- we've just got the resulting fully expanded text "echo a &" and no more alias. The nearest parallel to this case with normal aliases is this: alias foo='echo a &' % foo foo [1] 3423 a [2] 3424 % [1] - done echo a % a [2] + done echo a You'll see the underlying expansion behaviour is the same --- both aliases get expanded. This is long-standing and I assume is regarded as OK. I suppose we'd need some way of marking something as having had a suffix alias expanded before it, and then we'd need to reset that flag if we encountered something not at the start of that input that was in command position so we could expand a new suffix alias. However, I don't think it's quite as simple as the two separate tests - when expanding a suffix alias, set a lexical flag to say no more suffix aliases; - reset that flag any time you reach a new command position because in the problem case we have reached a new command position and don't want to reset the flag. So there's some subtle ordering to sort out. pws