RE: [EXTERNAL] - Re: This errors in 4.4, did not in 4.2: set -u; declare -A foo; echo ${#foo[@]}

[David Linden]

Thanks, and for the quick reply.

Language lawyers...

I'm curious what motivated the change.  Naively it seems creating a placeholder 
for a potential future array keeping track of attributes is more work than just 
creating an empty array.  The change is "surprising" to a user, at least this 
user.

-----Original Message-----
From: Greg Wooledge <greg@wooledge.org> 
Sent: Wednesday, November 6, 2024 10:26 PM
To: David Linden <dlinden@opentext.com>
Cc: bug-bash@gnu.org
Subject: [EXTERNAL] - Re: This errors in 4.4, did not in 4.2: set -u; declare 
-A foo; echo ${#foo[@]}

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On Thu, Nov 07, 2024 at 02:38:05 +0000, David Linden wrote:
> Description:
>       This errors in 4.4, did not in 4.2: set -u; declare -A foo; echo 
> ${#foo[@]}
>       How am I supposed to determine that a declared associative array is 
> empty?

The easiest way would be to ensure that the array variable is actually
created:

    set -u; declare -A foo=(); echo "${#foo[@]}"

Without the =() part, declare -A only creates a placeholder, which will assign 
the -A flag to a future variable named foo, if one is ever created.
You need an assignment to create the variable.