Shader:hasUniform
Gets whether a uniform / extern variable exists in the Shader.

If a graphics driver's shader compiler determines that a uniform / extern variable doesn't affect the final output of the shader, it may optimize the variable out. This function will return false in that case.
hasuniform = Shader:hasUniform( name )
name string The name of the uniform variable.
hasuniform boolean Whether the uniform exists in the shader and affects its final output.