Hi,

I'm using Wapp[1] to build a small web application.
To show some results previously saved in s SQLite database, there's this
code (simplified):
foreach descr $test {
wapp-trim "
<td>%html($descr)</td>
"
}

Some of descr have square brackets in their strings, like:
{"changed": false, "msg": "This has value ([])"}

As I'm using Tcl 8.6.13 the warning at https://wapp.tcl.tk/home/doc/trunk/
docs/commands.md applies:

Caution #1: When using Tcl 8.6 or earlier, command substitution, but not
variable substitution, occurs outside of the quoted regions. This problem
is fixed using the new "-command" option to the regsub command in Tcl 8.7.
Nevertheless, it is suggested that you avoid using the "[" character
outside of the %-quotes. Use "&#91;" instead.

My attempt to string map [ to the corresponding html code have failed,
like:

string map " {[} {&#91;} " $descr
string map { "[" "&#91;" } $descr

Also tried to escape the [, but to no success.

How can it be done?

Thanks,

Luís

[1] https://wapp.tcl.tk/

On 02 May 2024 12:22:33 GMT, Luis Mendes wrote:

> Hi,
>
> I'm using Wapp[1] to build a small web application.
> To show some results previously saved in s SQLite database, there's this
> code (simplified):
> foreach descr $test {
> wapp-trim "
> <td>%html($descr)</td>
> "
> }
>
> Some of descr have square brackets in their strings, like:
> {"changed": false, "msg": "This has value ([])"}
>
> As I'm using Tcl 8.6.13 the warning at
> https://wapp.tcl.tk/home/doc/trunk/" rel="nofollow" target="_blank">https://wapp.tcl.tk/home/doc/trunk/
> docs/commands.md applies:
>
> Caution #1: When using Tcl 8.6 or earlier, command substitution, but not
> variable substitution, occurs outside of the quoted regions. This
> problem is fixed using the new "-command" option to the regsub command
> in Tcl 8.7.
> Nevertheless, it is suggested that you avoid using the "[" character
> outside of the %-quotes. Use "&#91;" instead.
> [1] https://wapp.tcl.tk/

Upon further investigation, it seems that the problem doesn't happen
because of the [, but because of quotes.
I could already do the string map mentioned in the previous post.

If I try `set descr "\"changed\": false"
it breaks wapp.
The error returned is:
ERROR: extra characters after close-quote.

Although at that [1] web page it's said:
"""
wapp-subst TEXT
This command appends text to the end of reply to an HTTP request. The TEXT
argument should be enclosed in {...} to prevent accidental substitutions.
The "wapp-subst" command itself will do all necessary backslash
substitutions. Command and variable substitutions occur within
"%html(...)", "%url(...)", "%qp(...)", "%string(...)", and "%unsafe(...)".
The substitutions are escaped (except in the case of "%unsafe(...)") so
that the result is safe for inclusion within the body of an HTML document,
a URL, a query parameter, or a javascript or JSON string literal,
respectively.
"""

Luis Mendes <luisXXXlupeXXX@gmail.com> wrote:
> My attempt to string map [ to the corresponding html code have failed,
> like:
>
> string map " {[} {&#91;} " $descr
> string map { "[" "&#91;" } $descr
>
> Also tried to escape the [, but to no success.
>
> How can it be done?

Although your followup implies you no longer need the answer to this,
the way "to do it" is to feed a proper list to string map:

string map [list \[ "&#91;"] $descr

It is usually more difficult to try to create lists using "" or {} than
to just let the [list] command do so. In either of the first cases,
you have to have a very good internal understanding of what to quote
(and not to quote) to make the list correct. Using [list], it will
handle those details for you automatically.

Luis Mendes <luisXXXlupeXXX@gmail.com> wrote:
> On 02 May 2024 12:22:33 GMT, Luis Mendes wrote:
> Upon further investigation, it seems that the problem doesn't happen
> because of the [, but because of quotes.
> I could already do the string map mentioned in the previous post.
>
> If I try `set descr "\"changed\": false"
> it breaks wapp.
> The error returned is:
> ERROR: extra characters after close-quote.

What if you escape actual quotes into the html &quot; escape?

string map [list \" "&quot;"] $your_variable

On Thu, 2 May 2024 13:59:40 -0000 (UTC), Rich wrote:

> Luis Mendes <luisXXXlupeXXX@gmail.com> wrote:
>> My attempt to string map [ to the corresponding html code have failed,
>> like:
>>
>> string map " {[} {&#91;} " $descr string map { "[" "&#91;" } $descr
>>
>> Also tried to escape the [, but to no success.
>>
>> How can it be done?
>
> Although your followup implies you no longer need the answer to this,
> the way "to do it" is to feed a proper list to string map:
>
> string map [list \[ "&#91;"] $descr
>
> It is usually more difficult to try to create lists using "" or {} than
> to just let the [list] command do so. In either of the first cases, you
> have to have a very good internal understanding of what to quote (and
> not to quote) to make the list correct. Using [list], it will handle
> those details for you automatically.

Great tip Rich!
Thank you very much.

On Thu, 2 May 2024 14:01:12 -0000 (UTC), Rich wrote:

> Luis Mendes <luisXXXlupeXXX@gmail.com> wrote:
>> On 02 May 2024 12:22:33 GMT, Luis Mendes wrote:
>> Upon further investigation, it seems that the problem doesn't happen
>> because of the [, but because of quotes.
>> I could already do the string map mentioned in the previous post.
>>
>> If I try `set descr "\"changed\": false"
>> it breaks wapp.
>> The error returned is:
>> ERROR: extra characters after close-quote.
>
> What if you escape actual quotes into the html &quot; escape?
>
> string map [list \" "&quot;"] $your_variable
Wapp doens't break, but then the &quot; is not interpreted back to a "
when rendered in html.

I've substituted " by ' and it works, although not as accurate.
Thank you.

Luis Mendes <luisXXXlupeXXX@gmail.com> wrote:
> On Thu, 2 May 2024 14:01:12 -0000 (UTC), Rich wrote:
>
>> Luis Mendes <luisXXXlupeXXX@gmail.com> wrote:
>>> On 02 May 2024 12:22:33 GMT, Luis Mendes wrote:
>>> Upon further investigation, it seems that the problem doesn't happen
>>> because of the [, but because of quotes.
>>> I could already do the string map mentioned in the previous post.
>>>
>>> If I try `set descr "\"changed\": false"
>>> it breaks wapp.
>>> The error returned is:
>>> ERROR: extra characters after close-quote.
>>
>> What if you escape actual quotes into the html &quot; escape?
>>
>> string map [list \" "&quot;"] $your_variable
> Wapp doens't break, but then the &quot; is not interpreted back to a "
> when rendered in html.
>
> I've substituted " by ' and it works, although not as accurate.
> Thank you.

Then you might try escaping the quotes:

string map [list \" \\\"] $your_variable

And see if Wapp handles \" within the string properly.