pyln-client+cli: Fix formatting issues for plugin description in lightning-cli help

[NishantBansal2003]

Fixes: #8020

• Improved formatting of plugin descriptions displayed in the lightning-cli help output: Previously, the descriptions contained unnecessary \n characters when shown as a single line, which affected readability.
  Proposed Solution: Replace \n with | as the line separator when output is displayed in a single line, for better clarity and consistency.

• Removed unused variables and related code from pyln-client: For example, the doc variable in pyln/client/plugin.py was declared but never utilized, and related code was cleaned up to improve maintainability.

Important

24.11 FREEZE NOVEMBER 7TH: Non-bugfix PRs not ready by this date will wait for 25.02.

Checklist

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• The changelog has been updated in the relevant commit(s) according to the guidelines.
• Tests have been added or modified to reflect the changes.
• Documentation has been reviewed and updated as needed.
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[rustyrussell]

Great idea, I love it! Just need to make it specific to help output only, and fix commits a bit.

[rustyrussell]

This should be in the next commit?

Also, the Changelog line for the first commit is unnecessary: this isn't a user-visible change!

[rustyrussell]

human_readable() is used in other contexts, and this will break it. In particular, the summary plugin.

I think this replacement needs to occur inline:

static void replace_char(char *buf, size_t len, char old, char new)
{
     char *p = buf, *end = buf + len;
     while ((p = memchr(p, old, end - p)) != NULL)
          *p = new;
}

Then simply call replace_char(buffer + command->start, command->end - command_start, '|', '\n') here.

[NishantBansal2003]

Done; however, this part:

else if (buffer[i] == '|') {  
    fputc('\n', stdout);  
    continue;  
}  

is necessary for formatting the help output in cases of commands like lightning-cli help funds or lightning-cli help funds -H for external plugins such as funds.

[rustyrussell]

Hmm. In this case I think we have to use '\n' rather than abusing '|'. We now do this for plugin log messages, which makes it consistent. let me play...

[rustyrussell]

OK, how's that instead? More work, but closer to your original vision?

[NishantBansal2003]

OK, how's that instead? More work, but closer to your original vision?

I think this looks great. However, for output like the following, I’m not sure if we can do something about it:

$ lightning-cli help funds -J
{
   "help": [
      {
         "command": "funds [unit]  \n Lists the total funds the lightning node owns off- and onchain in {unit}.\n {unit} can take the following values:\n s, satoshi, satoshis to depict satoshis\n b, bit, bits to depict bits\n m, milli, btc to depict milliBitcoin\n B, bitcoin, btc to depict Bitcoins\n When not using Satoshis (default) the comma values are rounded off."
      }
   ],
   "format-hint": "simple"
}

$ lightning-cli help funds -R
{"help":[{"command":"funds [unit]  \n Lists the total funds the lightning node owns off- and onchain in {unit}.\n {unit} can take the following values:\n s, satoshi, satoshis to depict satoshis\n b, bit, bits to depict bits\n m, milli, btc to depict milliBitcoin\n B, bitcoin, btc to depict Bitcoins\n When not using Satoshis (default) the comma values are rounded off."}],"format-hint":"simple"}

$ lightning-cli help funds -F
help[0].command=funds [unit]  \n Lists the total funds the lightning node owns off- and onchain in {unit}.\n {unit} can take the following values:\n s, satoshi, satoshis to depict satoshis\n b, bit, bits to depict bits\n m, milli, btc to depict milliBitcoin\n B, bitcoin, btc to depict Bitcoins\n When not using Satoshis (default) the comma values are rounded off.
format-hint=simple

But for the most commonly used command, which is:

$ lightning-cli help funds

this output is great.