DownslopeFlowpathLength: --weights accept both raster and constant value

[jfbourdon]

Adds a --weight_val switch to allow input of weights as a single value instead of having to use a raster file. The --weights switch has been renamed --weights_file.

I initially wanted to keep the original --weights switch and allow it to accept both a raster file path and a number, but realised that the structure of the tool's parameters doesn't allow it (cleanly), that's my understanding at least. So I instead opt to add a new switch and rename the original one to avoid confusion between the two.

I haven't touch the python API yet, but will do when I'll get feedback on this proposal.

[brownag]

I think this would be a useful feature. But I my 2cents is that it would be best to find a way for --weights to accept both input types or at least leave the existing switch name unchanged for backward compatibility of scripts and various frontends.

[jfbourdon]

I agree that it would be the best thing from a user perspective, but doing so isn't very clean in the code so I don't know what @jblindsay would think of that.

The line 79 doesn't do any check so you can already pass a number as parameter:

whitebox-tools/whitebox-tools-app/src/tools/hydro_analysis/downslope_flowpath_length.rs

Lines 75 to 82 in 5545321

	parameters.push(ToolParameter {
	name: "Input Weights File (optional)".to_owned(),
	flags: vec!["--weights".to_owned()],
	description: "Optional input weights raster file.".to_owned(),
	parameter_type: ParameterType::ExistingFile(ParameterFileType::Raster),
	default_value: None,
	optional: true,
	});

The logic would just need to be changed a bit here to check whether the parameter passed is a file (check if the file exists) or is a number (check if it converts f32):

whitebox-tools/whitebox-tools-app/src/tools/hydro_analysis/downslope_flowpath_length.rs

Lines 247 to 251 in 5545321

	if !weights_file.is_empty() {
	use_weights = true;
	if !weights_file.contains(&sep) {
	weights_file = format!("{}{}", working_directory, weights_file);
	}

[jfbourdon]

I just found that the parameter type ExistingFileOrFloat exists (used for example in the InPlaceAdd tool). It's much cleaner that way and it avoids breaking backward compatibility.