Do not apply default values on data from database [2.x] #1706
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Before this change, when a property was configured with a default value at LoopBack side and the database was returned a record with a missing value for such property, then we would supply use the configured default. This behavior is problematic for reasons explained in #1692. In this commit, we are introducing a new model-level setting called `applyDefaultsOnReads`, which is enabled by default for backwards compatibility. When this setting is set to `false`, operations like `find` and `findOrCreate` will NOT apply default property values on data returned by the database (connector). Please note that most of the other CRUD methods did not apply default values on database data as long as the connector provided native implementation of the operation, that aspect is not changing. Also note that default values are applied only on properties with `undefined` values. The value `null` does not trigger application of default values. This is important because SQL connectors return `null` for properties with no value set.
3 tasks
jannyHou
approved these changes
Apr 9, 2019
| // And findOrCreate an existing record | ||
| return Player.findOrCreate({id: created.id}, {name: 'updated'}); | ||
| }) | ||
| .then(function(result) { |
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nitpick: I like the spread() function used in the original PR #1705, any reason switched back to then()?
Not a blocker for merging, just curious.
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In LB 3.x, we are using Bluebird as the promise library, therefore .spread() is available on all Promise instances.
In LB 2.x, we use the native Promise library if it's provided (Node.js 4.0 an higher), and require users to set global.Promise to any compatible Promise implementation on Node.js versions 0.10 & 0.12. The native Promise does not provide .spread() API.
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oh I see. makes sense thanks!.
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Before this change, when a property was configured with a default value at LoopBack side and the database was returned a record with a missing value for such property, then we would supply use the configured default.
This behavior is problematic for reasons explained in #1692.
In this commit, we are introducing a new model-level setting called
applyDefaultsOnReads, which is enabled by default for backwards compatibility.When this setting is set to
false, operations likefindandfindOrCreatewill NOT apply default property values on data returned by the database (connector).Please note that most of the other CRUD methods did not apply default values on database data as long as the connector provided native implementation of the operation, that aspect is not changing.
Also note that default values are applied only on properties with
undefinedvalues. The valuenulldoes not trigger application of default values. This is important because SQL connectors returnnullfor properties with no value set.Related issues
This is a back-port of #1705, which is a backport of #1704. Compared to #1704 (master/4.x), we are preserving backwards compatibility by introducing a new feature flag.
See also #1692.
/cc @sharathmuthu6 @snarjuna
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