Merge branch 'development'

Author: groue

.gitignore

@@ -112,3 +112,6 @@ Tests/SPM/Packages
 
 # Ruby
 .ruby-version
+
+# Test products
+Tests/products

CHANGELOG.md

@@ -7,6 +7,7 @@ GRDB adheres to [Semantic Versioning](https://semver.org/), with one exception:
 
 #### 5.x Releases
 
+- `5.13.x` Releases - [5.13.0](#5130)
 - `5.12.x` Releases - [5.12.0](#5120)
 - `5.11.x` Releases - [5.11.0](#5110)
 - `5.10.x` Releases - [5.10.0](#5100)
@@ -79,6 +80,24 @@ GRDB adheres to [Semantic Versioning](https://semver.org/), with one exception:
 
 ---
 
+## 5.13.0
+
+Released November 7, 2021 • [diff](https://github.com/groue/GRDB.swift/compare/v5.12.0...v5.13.0)
+
+- **Breaking Change**: [#1076](https://github.com/groue/GRDB.swift/pull/1076) by [@groue](https://github.com/groue): Require Swift 5.3 and Xcode 12
+- **New**: :star: [#1088](https://github.com/groue/GRDB.swift/pull/1088) by [@groue](https://github.com/groue): Shared ValueObservation
+- **New**: :star: [#1095](https://github.com/groue/GRDB.swift/pull/1095) by [@groue](https://github.com/groue): Precise foreign key checks for migrations
+- **New**: [#1078](https://github.com/groue/GRDB.swift/pull/1078) by [@groue](https://github.com/groue): Non-mutating persistence methods `saved` and `inserted`, and existence-checking methods `isEmpty` and `exists`
+- **New**: `DatabasePool.erase()` prevents concurrent reads until it has completed.
+- **New**: The `close()` method allows precise closing of database connections.
+- **New**: Filtering records by single-column primary key now properly encodes dates and uuids according to the customized strategies (`filter(id:)`, `deleteAll(_:keys:)`, etc.)
+- **New**: `DatabaseUUIDEncodingStrategy.lowercaseString` can encode UUID as a lowercased string. For clarity, the `string` strategy has been deprecated and renamed `uppercaseString`.
+- **Documentation Update**: :star: The [Concurrency Guide](Documentation/Concurrency.md) got a major overhaul.
+- **Documentation Update**: :star: A new [ValueObservation Sharing](README.md#valueobservation-sharing) chapter describes how to share database observations and spare database resources.
+- **Documentation Update**: :star: The [Migrations](Documentation/Migrations.md) guide tells how you can mitigate slow foreign key checks during schema changes.
+- **Documentation Update**: The [Date and UUID Coding Strategies](README.md#date-and-uuid-coding-strategies) chapter describes the new support for date and uuid primary key coding in requests by single-column primary key.
+- **Documentation Update**: A new [Testing for Record Existence](README.md#testing-for-record-existence) chapter describes the new `request.isEmpty(_:)`, `Record.exists(_:id:)` and `Record.exists(_:key:)` methods.
+
 ## 5.12.0
 
 Released September 25, 2021 • [diff](https://github.com/groue/GRDB.swift/compare/v5.11.0...v5.12.0)

CONTRIBUTING.md

@@ -118,7 +118,7 @@ Starting points:
 
 GRDB has a strong focus on safe concurrency. Not only safe as "does not crash", but safe as "actively protects your application data". The topic is discussed in (too) many places:
 
-- [Concurrency Guide](README.md#concurrency)
+- [Concurrency Guide](Documentation/Concurrency.md)
 - [Why Adopt GRDB?](https://github.com/groue/GRDB.swift/blob/master/Documentation/WhyAdoptGRDB.md#strong-and-clear-multi-threading-guarantees)
 - [Four different ways to handle SQLite concurrency](https://medium.com/@gwendal.roue/four-different-ways-to-handle-sqlite-concurrency-db3bcc74d00e)
 - [Good Practices for Designing Record Types](https://github.com/groue/GRDB.swift/blob/master/Documentation/GoodPracticesForDesigningRecordTypes.md#fetch-in-time)
@@ -313,7 +313,7 @@ Features that blur this focus are non-goals:
 [Non-Goals]: #non-goals
 [Report Bugs]: #report-bugs
 [RxGRDB]: http://github.com/RxSwiftCommunity/RxGRDB
-[Concurrency]: #concurrency
+[Concurrency]: Documentation/Concurrency.md
 [Sponsoring and Professional Support]: #sponsoring-and-professional-support
 [SQL Console in the Debugger]: #sql-console-in-the-debugger
 [SQLCipher in a Shared App Container]: #sqlcipher-in-a-shared-app-container

Documentation/Combine.md

@@ -191,7 +191,7 @@ let newPlayerCount = dbQueue.writePublisher { db -> Int in
 
 The difference is that the last fetches are performed in the `thenRead` function. This function accepts two arguments: a readonly database connection, and the result of the `updates` function. This allows you to pass information from a function to the other (it is ignored in the sample code above).
 
-When you use a [database pool], this method applies a scheduling optimization: the `thenRead` function sees the database in the state left by the `updates` function, and yet does not block any concurrent writes. This can reduce database write contention. See [Advanced DatabasePool](../README.md#advanced-databasepool) for more information.
+When you use a [database pool], this method applies a scheduling optimization: the `thenRead` function sees the database in the state left by the `updates` function, and yet does not block any concurrent writes. This can reduce database write contention. See [Advanced DatabasePool](Concurrency.md#advanced-databasepool) for more information.
 
 When you use a [database queue], the results are guaranteed to be identical, but no scheduling optimization is applied.
 
@@ -205,6 +205,7 @@ It completes on the main queue, unless you provide a specific [scheduler] to the
 Database Observation publishers are based on [ValueObservation] and [DatabaseRegionObservation]. Please refer to their documentation for more information. If your application needs change notifications that are not built as Combine publishers, check the general [Database Changes Observation] chapter.
 
 - [`ValueObservation.publisher(in:scheduling:)`]
+- [`SharedValueObservation.publisher()`]
 - [`DatabaseRegionObservation.publisher(in:)`]
 
 
@@ -250,6 +251,22 @@ This publisher has the same behavior as ValueObservation:
 See [ValueObservation Scheduling](../README.md#valueobservation-scheduling) for more information.
 
 
+#### `SharedValueObservation.publisher()`
+
+[SharedValueObservation] tracks changes in database values. You can turn it into a Combine publisher:
+
+```swift
+let sharedObservation = ValueObservation
+    .tracking { db in try Player.fetchAll(db) }
+    .shared(in: dbQueue)
+
+// A publisher with output [Player] and failure Error
+let publisher = sharedObservation.publisher()
+```
+
+This publisher has the same behavior as SharedValueObservation.
+
+
 #### `DatabaseRegionObservation.publisher(in:)`
 
 [DatabaseRegionObservation] notifies all transactions that impact a tracked database region. You can turn it into a Combine publisher:
@@ -374,14 +391,16 @@ let cancellable = hallOfFamePublisher.sink(
 [Demo Application]: DemoApps/GRDBCombineDemo/README.md
 [SQLite]: http://sqlite.org
 [ValueObservation]: ../README.md#valueobservation
+[SharedValueObservation]: ../README.md#valueobservation-sharing
 [`DatabaseRegionObservation.publisher(in:)`]: #databaseregionobservationpublisherin
 [`ValueObservation.publisher(in:scheduling:)`]: #valueobservationpublisherinscheduling
+[`SharedValueObservation.publisher()`]: #sharedvalueobservationpublisher
 [`readPublisher(receiveOn:value:)`]: #databasereaderreadpublisherreceiveonvalue
 [`writePublisher(receiveOn:updates:)`]: #databasewriterwritepublisherreceiveonupdates
 [`writePublisher(receiveOn:updates:thenRead:)`]: #databasewriterwritepublisherreceiveonupdatesthenread
 [`migratePublisher(_:receiveOn:)`]: Migrations.md#asynchronous-migrations
 [configured]: ../README.md#databasepool-configuration
 [database pool]: ../README.md#database-pools
 [database queue]: ../README.md#database-queues
-[database snapshot]: ../README.md#database-snapshots
+[database snapshot]: Concurrency.md#database-snapshots
 [scheduler]: https://developer.apple.com/documentation/combine/scheduler