Merge pull request #12177 from rubberbaron/prompt-parse-whitespace-around-numbers

!emphasized: "(" prompt ")"

        | "(" prompt ":" prompt ")"

        | "[" prompt "]"

scheduled: "[" [prompt ":"] prompt ":" [WHITESPACE] NUMBER "]"

scheduled: "[" [prompt ":"] prompt ":" [WHITESPACE] NUMBER [WHITESPACE] "]"

alternate: "[" prompt ("|" prompt)+ "]"

WHITESPACE: /\s+/

plain: /([^\\\[\]():|]|\\.)+/

        class CollectSteps(lark.Visitor):

            def scheduled(self, tree):

                tree.children[-1] = float(tree.children[-1])

                if tree.children[-1] < 1:

                    tree.children[-1] *= steps

                tree.children[-1] = min(steps, int(tree.children[-1]))

                res.append(tree.children[-1])

                tree.children[-2] = float(tree.children[-2])

                if tree.children[-2] < 1:

                    tree.children[-2] *= steps

                tree.children[-2] = min(steps, int(tree.children[-2]))

                res.append(tree.children[-2])

            def alternate(self, tree):

                res.extend(range(1, steps+1))

    def at_step(step, tree):

        class AtStep(lark.Transformer):

            def scheduled(self, args):

                before, after, _, when = args

                before, after, _, when, _ = args

                yield before or () if step <= when else after

            def alternate(self, args):

                yield next(args[(step - 1)%len(args)])

\\|

\(|

\[|

:([+-]?[.\d]+)\)|

:\s*([+-]?[.\d]+)\s*\)|

\)|

]|

[^\\()\[\]:]+|