fix(TranslatePipe): handle non string input

[jrolheiser]

I didn't see a contributing guideline and I wasn't sure if I sure file a bug for this/wanted to start more of a discussion about how TranslatePipe should handle non-string input.

Preface

I write shared components for other teams to use (think asset kit), and don't have strict control over inputs. We can put in arg validation as needed but I did run into a case that IMO the TranslatePipe should handle on its own.

Problem

TranslatePipe throws a Parameter "key" required error for number type input. IMO this could just return back the number that was passed in, curious on others' opinions?

Example

We have a shared filtering/searching component that displays a list of filter labels the user can select from such as:

The basic replication code boils down to:

<span>{{ 2018 | translate }}</span>

Which throws the Parameter "key" required error.

Solution

Return back the original query arg if it is falsey or the .length call is falesy.

Discussion

Curious if others agree if this should be the functionality or if I have to resort to coercing all inputs to strings in my components.

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@ocombe