Inactive branches of code isn't highlighted with custom theme

Problem

When using a bundled theme, Rider or CLion Nova correctly highlights code in inactive code branches, for e.g.: Theme: Islands Dark; Colorscheme: Rider Islands Dark:

However, once installing a custom theme from the marketplace, this highlighting stops working, and only a limited number of keywords are highlighted, for e.g.:

Explanation

The inactive code branch highlighting is implemented in Rider that way that the theme itself should specify how to render the inactive code. If a theme doesn't specify it, the result is as shown above.

Solution

As a user of a theme with such an issue

• Open Settings | Editor | Color Scheme;

• Export the necessary colorscheme as a .icls:

• Open the .icls for edit and add the following option as a child element under <attributes>: (! option is different for CLion, see below)

      <option name="ReSharper.C_PREPROCESSOR_INACTIVE_BRANCH_V2">
        <value>
          <option name="EFFECT_COLOR" value="FF00FF" />
          <option name="EFFECT_TYPE" value="6" />
        </value>
      </option>
  

• So that the resulting file looks like:

  <scheme name="ThemeName" version="142" parent_scheme="Darcula">
    <metaInfo>...</metaInfo>
    <colors>...</colors>
    <attributes>
      ...
      <option name="ReSharper.C_PREPROCESSOR_INACTIVE_BRANCH_V2">
        <value>
          <option name="EFFECT_COLOR" value="FF00FF" />
          <option name="EFFECT_TYPE" value="6" />
        </value>
      </option>
      ...
    </attributes>
  </scheme>
  

• Save the changes and import the updated colorscheme from Rider (Settings | Editor | Color Scheme | Cog | Import Scheme):

• Once it is done, the highlighting in inactive code branches should start working for that particular color scheme;

As a theme developer

When one bundles a colorscheme together with a theme, one has ThemeName.json and ThemeName.xml . For the inactive code highlighting to work with a colorscheme, it is necessary to specify it in the .xml file of a colorscheme, for e.g: (! option is different for CLion, see below):

<scheme name="ThemeName" version="142" parent_scheme="Darcula">
  <metaInfo>...</metaInfo>
  <colors>...</colors>
  <attributes>
    ...
    <option name="ReSharper.C_PREPROCESSOR_INACTIVE_BRANCH_V2">
      <value>
        <option name="EFFECT_COLOR" value="FF00FF" />
        <option name="EFFECT_TYPE" value="6" />
      </value>
    </option>
    ...
  </attributes>
</scheme>

Additional notes:

• The option for CLion is:

    <option name="OC.CONDITIONALLY_NOT_COMPILED_V2">
      <value>
        <option name="EFFECT_TYPE" value="6"/>
        <option name="EFFECT_COLOR" value="616161"/>
      </value>
    </option>
  

• EFFECT_TYPE=6 is a transparent effect. The value of EFFECT_COLOR is in fact ignored by IDE, but it still necessary to specify it.