0011 - Use constants for configuration variables

0011-use-constantas-for-configuration-variables.md

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+# 11. Use constants for configuration variables
+
+Date: 2020-01-05
+
+## Status
+
+In discussion
+
+## Context
+
+Configuration names in PrestaShop are used as hardcoded strings.
+For example:
+
+    PS_SSL_ENABLED
+    PS_SHOP_ENABLE
+
+It makes it harder to figure out which configurations are available, also leaves possibility for mistyping configuration name without noticing.
+
+If some Configuration is no longer used, there is no proper process to deprecated it, leading to configurations like 
+
+    PS_CONFIGURATION_AGREMENT 
+
+cluttering database, but not having any actual use.  
+
+## Decision
+
+Use constants in Configuration class to define all the configuration names and then use them in code instead of plain strings. 
+So in code we would have `Configuration::updateValue(Configuration::PS_SSL_ENABLED, 1);` instead of `Configuration::updateValue('PS_SSL_ENABLED', 1);`
+
+This would also allow for you to have a documentation of sorts for configuration names, by having them all in one place.
+
+### Why use Configuration class
+It already exists for all purposes concerning usage of configurations. Creation of the new class just to store
+constants is not worthwhile in this case.
+
+## First implementation
+
+https://github.com/PrestaShop/PrestaShop/pull/22672
+
+## Consequences
+
+What becomes easier :
+
+- You can't miss-write configuration name
+- Using constants uses less memory than plain string
+- You can change the name of constant without considering it as breaking change
+- It's easier to refactor
+- When all configuration names are in one place, it's easier to fine one you are looking for
+- Allows deprecating configurations
+- Allows to document Configurations in code
+
+What becomes harder :
+- You need to include(use or require) Configuration class everywhere, you want to use Configurations
+- Need to replace Configuration names with constants for this to be useful, which will require some work and testing