Add React performance warnings #239
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Note: This PR is currently a draft and untested, because of a build issue that currently prevents tests from running in the repo. @jerzy-mankowski has said they will address it when they have time. I will revise this PR afterward with a set of passing E2E tests at that time.
This PR includes a draft of 2 new performance warnings for the React AdvancedImage element. Please see the accompanying issue for a full description of the rationale for these two warnings.
The warnings are:
warnOnOversizedImage: Logs a warning when an image is loaded, and the intrinsic size is greater than the rendered size by a substantial margin. That margin is defined inOVERSIZE_IMAGE_TOLERANCEand initially set to 500.warnOnLazyLCP: Logs a warning when the PerformanceObserver API detects an image is a candidate for the LCP image but has been loaded withloading=“lazy”.Both warnings only fire if the NODE_ENV variable is present (true in most React apps) and set to “development”. Both warnings can be silenced if the AdvancedImage element is given an attribute called “silence-warnings”.