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Fix duplicate default layer with a custom layer filter - #427
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LayerContents::load decided whether to synthesize an empty default layer by checking LayerFilter::includes_default_layer(), which only knows about the all/load_default flags. A custom filter_layers closure that admitted the real default layer got the placeholder pushed anyway, so the layer set ended up with two entries pointing at glyphs/, and saving would nondeterministically clobber the real layer's contents.plist with the empty one's. Push the placeholder only when no loaded layer already has the default glyphs directory, and still fall through to MissingDefaultLayer when all/load_default was requested but the UFO genuinely has no default layer.
anthrotype
reviewed
Oct 7, 2026
| fn test_filter_admits_default_layer_no_duplicate() { | ||
| let ufo_path = "testdata/MutatorSansLightWide.ufo"; | ||
| let request = DataRequest::none() | ||
| .filter_layers(|name, _path| name == "public.default" || name == "foreground"); |
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the docstring says the filter admits the default layer "by name or by path", but the test only goes by name (and "public.default" doesn't match anything in this fixture, the default layer is called "foreground"). Maybe you can add a second request with |_, p| p == Path::new("glyphs"), since a path-only filter hits the same duplicate on main
anthrotype
approved these changes
Oct 7, 2026
A path-only filter hit the same duplicate layer bug. Also drop the public.default check, which never matched in this UFO.
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another funny little bug I found in the course of some other work:
LayerContents::load decided whether to synthesize an empty default layer by checking LayerFilter::includes_default_layer(), which only knows about the all/load_default flags. A custom filter_layers closure that admitted the real default layer got the placeholder pushed anyway, so the layer set ended up with two entries pointing at glyphs/, and saving would nondeterministically clobber the real layer's contents.plist with the empty one's.
Push the placeholder only when no loaded layer already has the default glyphs directory, and still fall through to MissingDefaultLayer when all/load_default was requested but the UFO genuinely has no default layer.