Parse command string with nested quotes into arguments and flags

Question

I'm trying to create a command parser for a Discord bot for when it receives a message, but I am having issues with dealing with nested quotes. I have made it so that it can parse a string with double quotes and flags, but it does not handle nested quotes.

Here are my requirements:

Handle double quotes.
Handle nested double quotes.
Handle flags (can be anywhere after !command).
- A flag without a specified value defaults to a value of true/1.

For example, the following string:

!command that --can "handle double" quotes "and \"nested double\" quotes" --as --well=as --flags="with values"

...should result in the following arguments: command, that, handle double, quotes, and "nested double" quotes and the following flags: "can": true, "as": true, "well": "as", "flags": "with values".

Here is what I have so far:

// splits up the string into separate arguments and flags
const parts = content.slice(1).trim().match(/(--\w+=)?"[^"]*"|[^ "]+/g)
  .map(arg => arg.replace(/^"(.*)"$/, '$1'));

// separates the arguments and flags
const [ args, flags ] = parts.reduce((parts, part) => {
  // check if flag or argument
  if (part.startsWith('--')) {
    // check if has a specified value or not
    if (part.includes('=')) {
      // parses the specified value
      part = part.split('=');
      const value = part.slice(1)[0];

      parts[1][part[0].slice(2)] = value.replace(/^"(.*)"$/, '$1');
    } else {
      parts[1][part.slice(2)] = true;
    }
  } else {
    parts[0].push(part);
  }

  return parts;
}, [[], {}]);

This currently parses into the following arguments: command, that, handle double, quotes, and \, nested, double\, quotes and the following flags: "can": true, "as": true, "well": "as", "flags": "with values".

Daemon Beast · Accepted Answer · 2020-11-14 11:58:14Z

1

I modified the first RegEx to allow \" in the middle of quoted values. The following line:

const parts = content.slice(1).trim().match(/(--\w+=)?"[^"]*"|[^ "]+/g)

...changed to:

const parts = content.slice(1).trim().match(/(--\S+=)?"(\\"|[^"])*"|[^ "]+/g)

Modifications

The "[^"]*" section was changed to "(\\"|[^"])*" to allow \" to validate, preventing the quoted value from being terminated by quotes with backslashes before them.
I changed the \w in (--\w+=)? to a \S resulting in (--\S+=)? to allow more letters to validate.

answered Nov 14, 2020 at 11:58

Daemon Beast

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2 Comments

Jaredo Mills Over a year ago

This doesn't work generally. With the test input cc -E -Dquote='"\""' -c test.c, the third matched group should be -Dquote='"\""', but it is not. See regex101.com/r/mtDDNU/1 - I don't know how to fix your regex, or if it's fixable; just wanted to point out in case someone else considers this wrong answer as a solution

Jaredo Mills Over a year ago

BTW, my counter example defines a preprocessor macro named quote which is a quoted string containing one character: the double quote (")

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