Reflect metadata polyfill is no longer automatically provided in JIT mode Reflect metadata support is not required by Angular in JIT applications compiled by the CLI. Applications built in AOT mode did not and will continue to not provide the polyfill. For the majority of applications, the reflect metadata polyfill removal should have no effect. However, if an application uses JIT mode and also uses the previously polyfilled reflect metadata JavaScript APIs, the polyfill will need to be manually added to the application after updating. To replicate the previous behavior, the core-js package should be manually installed and the import 'core-js/proposals/reflect-metadata'; statement should be added to the application's polyfills.ts file. ## Deprecations ### @angular/cli
The defaultCollection workspace option has been deprecated in favor of schematicCollections.

Before json "defaultCollection": "@angular/material"

After json "schematicCollections": ["@angular/material"]

The defaultProject workspace option has been deprecated. The project to use will be determined from the current working directory. ### @angular-devkit/core
- ContentHasMutatedException, InvalidUpdateRecordException, UnimplementedException and MergeConflictException symbol from @angular-devkit/core have been deprecated in favor of the symbol from @angular-devkit/schematics.
- UnsupportedPlatformException - A custom error exception should be created instead. ### @schematics/angular | Commit | Description | | -- | -- | | | add migration to remove defaultProject in workspace config | | | Consolidated setup with a single beforeEach() | | | fix extra comma added when use --change-detection=onPush and --style=none to generate a component | ### @angular/cli | Commit | Description | | -- | -- | | | add ng cache command | | | add support for multiple schematics collections | | | deprecated defaultProject option | | | ng g show descrption from collection.json if not present in schema.json | | | display package manager during ng update | | | hide private schematics from ng g help output | | | print entire config when no positional args are provided to ng config | | | remove analytics prompt postinstall script | ### @angular-devkit/build-angular | Commit | Description | | -- | -- | | | add node_modules prefix to excludes RegExp | | | allow Workers in Stackblitz | | | don't override asset info when updating assets | | | remove unneeded JIT reflect metadata polyfill | ### @angular-devkit/core | Commit | Description | | -- | -- | | | add Angular CLI major version as analytics dimension | | | deprecate unused exception classes | ### @angular-devkit/schematics | Commit | Description | | -- | -- | | | add parameter to listSchematicNames to allow returning hidden schematics. | ### @ngtools/webpack | Commit | Description | | -- | -- | | | update peer dependency to reflect TS 4.6 support | ## Special Thanks Adrien Crivelli, Alan Agius, Charles Lyding, Doug Parker, Paul Gschwendtner, Tobias Speicher, alkavats1 and gauravsoni119