Is inlining a console.warn the way how we notice about depreciations? I think using _doing_it_wrong() is a safer approach.

This is probably from line 1171, but I would love to hear what @gziolo thinks about that.

The backcompat was actually suggested by @jorgefilipecosta so I've left it unchanged.

Should I remove the wp_add_inline_script part and introduce the _doing_it_wrong() for both instances of console.warn?

At the time of my suggestion _doing_it_wrong was not yet available.
I think we can now use the following:
_doing_it_wrong(
'add_theme_support()',
__( 'Setting colors using multiple parameters is deprecated. Please pass a single parameter with an array of colors. See https://wordpress.org/gutenberg/handbook/extensibility/theme-support/ for details.', 'gutenberg' ),
'3.2.0'
);

@Luehrsen and @jorgefilipecosta I've went ahead and applied the _doing_it_wrong on both console.warn instances.

Do I guess the usage right, that you want to create the array somewhat programatically and just pass a variable to add_theme_support?

All in all I think it is a good method of doing things.

@Luehrsen I won't speak for @webmandesign but that's what we'd like to do. Also makes it a little easier to re-use the color values in other contexts, e.g. auto-generating inline CSS for the classes, etc.

(something like…

$colors = [ /* imagine I'm an array */ ];

add_theme_support( 'editor-color-palette', $colors );

foreach ( $colors as $color ) {
 $css .= ".{$color['name']} { color: {$color['color']} }\n"
}

// echo out $css somewhere

Although I like the approach, I would probably have done that with get_theme_support(). I think that would add consistency throughout the themes and coding standards, as I would just have to search for 'editor-color-palette' to see all code that handles the theme colors.

foreach( get_theme_support( 'editor-color-palette' ) as $color ) {
     $css .= ".{$color['name'} { color: {$color['color']} }\n"
}

@Luehrsen That works as well! My code was just an example — but having a consistent input and output format makes sense I think, either way.

@Luehrsen Yes, that's correct, I want to create the array programatically and then just pass it into add_theme_support. I think that's the best approach (right now I can't think of any other add_theme_support feature being passed with multiple arguments nowadays, actually).

+1 for changing this to using _doing_it_wrong() instead of printing a JS warning. After all it's something done wrong in PHP. :)

This is a solid implementation of BC, just a minor detail I think we should improve: I don't like calling get_theme_support() twice. I think we should make the original call to set $color_palette be only the (array) get_theme_support( 'editor-color-palette' ) part.

Then the if clause could check ! empty( $color_palette ) && isset( $color_palette[0]['color'] ), and if so, trigger the notice. Then an else clause could get the first array element to account for the new way.

One thing I'm not sure about, why is there an is_string() check. I might miss something, was it possible to provide strings only at some point?

@felixarntz
From my tests, we can not use (array) get_theme_support( 'editor-color-palette' ) width ! empty( $color_palette ) check as if the theme does not claim the support, this would be returned (which is not en empty array):

array(1) {
	[0] => bool(false)
}

The is_string() check is there to accommodate the old way of setting colors as add_theme_support( 'editor-color-palette', '#fff', '#000', ... );. Then this was updated to setting colors with multiple array arguments.

This code should do the trick though:

	$color_palette           = (array) get_theme_support( 'editor-color-palette' );

	// Backcompat for Color Palette set as multiple parameters.
	if ( is_string( $color_palette[0] ) || isset( $color_palette[0]['color'] ) ) {
		_doing_it_wrong(
			'add_theme_support()',
			__( 'Setting colors using multiple parameters is deprecated. Please pass a single parameter with an array of colors. See https://wordpress.org/gutenberg/handbook/extensibility/theme-support/ for details.', 'gutenberg' ),
			'3.4.0'
		);
	} else {
		$color_palette = current( $color_palette );
	}

@felixarntz I've went ahead and created #7695 addressing your concerns. Thanks for pointing this out!