Polymer 2.0 in 2.0 seconds: Upgrading Projects Large and Small
summary
Polymer 2 introduces hybrid mode so elements run unchanged on Polymer 1 or 2 at runtime, using compatibility shims for renamed APIs (attached → connected, content → slot) and incremental syntax support in 1.7. A code rewrite tool, Polymer upgrader, automates mechanical fixes in place, while an updated linter flags nonhybrid patterns and Web Component Tester runs tests against both versions with one command. Migration is minimally breaking and designed to roll across large codebases.
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