Re: Alias/heredoc/cmdsubst regression

[Harald van Dijk <harald@gigawatt.nl>]

On 24/01/2020 23:48, Martijn Dekker wrote:
> There is a regression involving alias expansion, a here-document, and a 
> command substitution. The following worked fine until dash 0.5.8; it 
> throws a syntax error as of dash 0.5.9.
> 
> alias BEGIN='{' END='}'
> BEGIN
> cat <<eof
> $(echo hi)
> eof
> END

Nice find.

When the newline after cat <<eof is seen, checkkwd is changed to 
indicate that the shell is in a state where aliases can be expanded. 
Then, parseheredoc() is called, which in turn calls readtoken1() to 
parse the here-document. readtoken() re-sets checkkwd once it is done, 
but readtoken1() does not, so normally this preserves the "can expand 
aliases" state. However, nested command substitutions do reset checkkwd, 
so things break.

Until 0.5.8, parseheredoc() was called first, and only after that did 
checkkwd get changed.

Either parseheredoc() needs to save and restore checkkwd, or the code 
calling parseheredoc() needs to ensure that it sets checkkwd as 
appropriate afterwards.

Cheers,
Harald van Dijk