Backward compatible development in examples. Magento unconference in Lviv by Atwix 2019

1. Backward Compatible Development In Examples
Sergii Ivashchenko | Magento Community Engineering

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Radio: Mono -> Stereo
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Mono radio station implementation
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Extended implementation reuse original
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Add new extended/improved implementation?
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Backward Incompatible Approach Backward Compatible Approach
Introduce new implementation to
compete with existing Proxy old method calls to new
introduced interfaces/classes

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Money: Cache -> Check -> Card -> Contactless
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Deprecation
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Replace existing implementation with newer and better
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Backward Incompatible Approach Backward Compatible Approach
Remove existing implementation and
refactor code to use new one
Introduce new implementation and mark
old as deprecated
(there’s a small nuance - see few slides later)

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MacBook: USB -> USB-C
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Adapter
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Introducing new interface, adapting old
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Get rid of old ugly implementation
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Backward Incompatible Approach Backward Compatible Approach
Remove existing implementation and
refactor code to use new one
Proxy old method calls to new
introduced interfaces/classes
(use deprecated tag)

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Is adding new staff backward compatible?
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Adding a new non-private method
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Even more likely…
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Adding a new non-private property
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Even more likely…
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Adding a new non-private constant
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Even more likely…
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A couple of backward incompatible changes
that is not so easy to identify:
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Adding a functionality replacement without reusing existing interfaces
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Declaring a constructor with optional parameters
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There should be no obstacles for making things better
▪ Backward compatible development guide:
▪ https://devdocs.magento.com/guides/v2.3/contributor-guide/backward-compatible-
development/
▪ Be aware of introduced backward incompatible changes:
▪ https://devdocs.magento.com/guides/v2.3/release-notes/backward-incompatible-
changes/
▪ Discuss if not sure:
▪ Slack channel: #appdesign
▪ Public Architecture Discussion meeting every Wednesday, 18:30 Lviv time
▪ https://github.com/magento/architecture/wiki
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25. @sergeivaschneko
Lviv 2019