| source | A string that contains a shader written in ShaderLab code. |
| compileInitialShaderVariants | Set to true to compile the ShaderLab code contained in the source string; otherwise false. |
| shader | The Shader to update. |
Replaces the existing source code in the specified shader with the source code in the supplied string. The override provides a boolean that specifies whether the shader should be recompiled.