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# Error: $compile:missingattr
Missing required attribute

    Attribute '{0}' of '{1}' is non-optional and must be set!

## Description

This error may occur only when `$compileProvider.strictComponentBindingsEnabled` is set to `true`.

If that is the case, then all component controller bindings and directive scope / controller bindings that are non-optional, must be provided when the directive is instantiated.

To make a binding optional, add '?' to the definition.

## Example:

    app.component('myTest', {
      bindings: {
        first: '=?', // optional
        second: '='
      },
      controller: function() {
        ...
      },
      template: '...'
    });

This component will throw `missingattr` for the `second` binding when used as follows:

    <my-test></my-test>