Make actions (more) pure

[johnfn]

Currently, executing an action will, if that action manipulates text, cause that action to immediately update the document. Seems logical, but it doesn't work well in the case of . and macros because they potentially can trigger hundreds of insertions and deletions.

The correct solution is to batch all updates and deletes into a single step which we send off to VSCode. However, this will requires a lot of care. VSCode does not support batching operations that operate on overlapping regions, so we'll have to accommodate for that.

Here's my game plan for this.

• Make actions pure where possible.

Refactor every action such that inserts or deletes text to associate with itself an object that indicates what should happen to the document - { type: "insert", location: some position, text: "whatever" }

• For some actions, make them pure eventually

For some actions like direct text insertion, we can't be sure exactly what text will be inserted into the document until we actually update vscode. (For example, if you type "(", vscode actually inserts "()". There are many cases like this, and we can't possibly account for all of them manually.)

For these actions, we'll need to associate some sort of placeholder object like { type: 'insert', text: 'i dont know yet!' } This object will get overwritten to contain the correct text once we see that vscode has updated the document.

• When we run . or a macro, merge all these objects together. Merge history changes into a single operation. Fixes #427 #496 is a good first start at this.

[johnfn]

I actually did this with my multi cursor mode branch. Woo