[PATCH] hush: Fix assignments being misinterpreted as commands

[Heinrich Schuchardt]

On 3/1/21 3:17 PM, Tom Rini wrote:
> On Sun, Feb 28, 2021 at 06:51:53PM -0500, Sean Anderson wrote:
>> On 2/28/21 6:40 PM, Heinrich Schuchardt wrote:
>>> Am 28. Februar 2021 22:29:51 MEZ schrieb Sean Anderson <seanga2 at gmail.com>:
>>>> If there were no variable substitutions in a command, then initial
>>>> assignments would be misinterpreted as commands, instead of being
>>>> skipped
>>>> over. This is demonstrated by the following example:
>>>>
>>>> 	=> foo=bar echo baz
>>>
>>> The commit message does not explain why this patch is needed.
>>
>> This is a bug I noticed while writing some tests of hush.
>>
>>> What shall be the value off foo after this line?
>>
>> It should be bar. This is an existing difference when compared with
>> bash. For example, without this patch, we have
>>
>> 	=> foo=bar echo $foo
>> 	bar
>> 	=> echo $foo
>> 	bar

This seems really awkward. In bash I get:

$ foo=bar ./test.sh
bar
$ echo $foo

$

Where test.sh

#!/bin/sh
echo $foo

I did not expect an assignment made before a command to stick.

>>
>>>
>>> What will be the output of
>>>
>>> foo=bar echo ${foo}
>>>
>>> with and without your patch?
>>
>> It is the same.

Please, provide an example where the patch makes a difference.

Best regards

Heinrich

>
> bash works as you describe.  dash and busybox-sh both function like
> this:
> $ foo=bar echo $foo
>
> $ echo $foo
>
> $
>
> That we error out entirely is different from everyone.  Is that a good
> thing?  Maybe.  I know I've caught myself making thinkos due to that
> logic.  It does also violate the principal of least surprise, that we
> don't act like anything else.  But I would suggest the behavior of
> busybox-sh (what we forked long long ago) is what we should model here
> rather than be more bash-like.  I'm not all that firm on this opinion
> frankly, especially given the one-line nature of the change to bring us
> that behavior and I assume dash/busybox are acting like pure sh would in
> this case, which we aren't anyhow.
>