feat: add a way to spawn populated LineEditor

[ekorchmar]

Closes #6002

Adds a new constructor for LineEditor, that allows to specify text to pre-populate the input.
Also removes a call to line.clear() in a method to initiate editing, as it is currently only ever called after editor struct had been newly spawned.

[wez]

Thanks for this! Please rebase this PR as there is a partial conflict with #6054

I have a couple of suggestions, but this otherwise looks good!

[ekorchmar]

Rebased onto new master and implemented requested changes.

[wez]

Let's tag this with the version it was introduced with:

Suggested change

	the input.
	the input. {{since('nightly', inline=True)}}

[wez]

ah, I didn't spot this initially. I think this is a big semantic change that breaks behavior. You can probably see this in the debug overlay (ctrl-shift-L) if you type in foo and hit enter. Does it cause foo to show up in the next line?

What I think should be done here is to adjust this method:

fn read_line_impl(&mut self,
    host: &mut dyn LineEditorHost,
    initial_value: Option<&str>
) -> Result<Option<String>> {
    self.line.clear();
    if let Some(value) = initial_value {
        self.line.set_line_and_cursor(value, value.len());
    }

Then, refactor:

pub fn read_line(&mut self, host: &mut dyn LineEditorHost) -> Result<Option<String>>

into

pub fn read_line_with_optional_initial_value(&mut self, host: &mut dyn LineEditorHost, initial_value: Option<&str>) -> Result<Option<String>>

that calls the above function:

...
let res = self.read_line_impl(host, initial_value);
...

Then finally add back the original method, but make it call the refactored one:

pub fn read_line(&mut self, host: &mut dyn LineEditorHost) -> Result<Option<String>> {
   self.read_line_with_optional_initial_value(host, None)
}

Note that the public methods on this struct need to have doc comments because they are part of the public API that is published to https://docs.rs/termwiz/latest/termwiz/lineedit/struct.LineEditor.html

[ekorchmar]

I think this is a big semantic change that breaks behavior. You can probably see this in the debug overlay (ctrl-shift-L) if you type in foo and hit enter. Does it cause foo to show up in the next line?

From what I can test, it does not appear as if removal of this line causes old contents to appear anywhere; I tested various combinations of launching REPL, custom editor, pressing enter, cancelling input with Esc and Ctrl+C and other things.

If I read the code correctly, in every instance where a LineEditor struct is spawned, it's read_line method is only ever called once, with no loops. As such, the "clear" function does not actually do anything: it only ever sees an already empty, freshly created line.

[wez]

The termwiz crate is a public export and used by others, so just looking at the usage within wezterm is not sufficient to determine that nothing is impacted by this change.

I went ahead and merged this with my suggested changes.

Thank you!

[ekorchmar]

This makes sense. Thank you for reviewing this

[wez]

with the above changes, this would become:

Suggested change

	if let Some(value) = &args.initial_value {
	editor.set_line_and_cursor(value, value.len());
	}
	let line = editor.read_line(&mut host)?;
	let line = editor.read_line_with_optional_initial_value(&mut host, args.initial_value.as_deref())?;