Changing between "find" and "replace" in regex mode corrupts state of find widget

[thw0rted]

• VSCode Version: Code 1.14.2 (cb82feb, 2017-07-19T23:26:08.116Z)
• OS Version: Linux x64 4.10.0-28-generic
• Extensions:

Extension	Author (truncated)	Version
xml	Dot	1.9.2
EditorConfig	Edi	0.9.4
html-css-class-completion	Zig	1.8.0
path-intellisense	chr	1.4.2
vscode-svgviewer	css	1.4.2
vscode-eslint	dba	1.2.11
githistory	don	0.2.2
tslint	eg2	0.17.0
Angular2	joh	2.4.0
debugger-for-chrome	msj	3.1.7
vetur	oct	0.9.3
vscode-icons	rob	7.12.0

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Steps to Reproduce:

1. CTRL+F to show find widget, set Regex mode
2. Type a simple regular expression that matches some text in your document. Make some minor changes by typing part of the expression, deleting with backspace, maybe move around the text field with the arrow keys.
3. CTRL+Z / CTRL+Y several times to undo/redo typing the expression. Redo until the expression is complete, and ensure that some text in your document matches and gets highlighted.
4. Once your expression matches something on the page, press CTRL+H. The "Find" field should change from the expression you just typed to the literal value that was matched. (This is unexpected behavior, IMHO, but isn't the worst part.) Your focus should now be in the "Replace" box.
5. Tab or click back to the "Find" field.
6. CTRL+Z several times, then CTRL+Y several times, to move back and forth through your undo history. You should see several characters erased, then replaced with totally different characters as matched literal text is "un-done" and regular expression control characters are "re-done".

Expected behavior:

Ideally, CTRL+F / CTRL+H would only populate the "Find" box with the document selection when it's currently empty. If you're going to insist on doing this, the undo/redo history should have one entry added at the end that consists of totally erasing the current contents and replacing them with the matched text, as though you had copied the text, selected the contents of the "Find" box, then pasted.

[rebornix]

If you don't like the auto population of selection, you can disable it by setting editor.find.seedSearchStringFromSelection to false.

The undo/redo history issue is tracked in #27035

[thw0rted]

I don't want to turn seedSearchString off for most cases, I like that it populates the widget when it was not already open. The problem is that you can't use "find" to find something then switch to "replace", at least in regex mode, because of the behavior I described in bullet 4 of the OP. Should I file a separate suggestion to change the behavior to only "seed" when the widget is first opened?