mirror of
https://github.com/JohnEstropia/CoreStore.git
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264 lines
8.8 KiB
Swift
264 lines
8.8 KiB
Swift
//
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// MigrationChain.swift
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// CoreStore
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//
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// Copyright © 2015 John Rommel Estropia
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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//
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import Foundation
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import CoreData
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// MARK: - MigrationChain
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/**
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A `MigrationChain` indicates the sequence of model versions to be used as the order for progressive migrations. This is typically passed to the `DataStack` initializer and will be applied to all stores added to the `DataStack` with `addSQLiteStore(...)` and its variants.
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Initializing with empty values (either `nil`, `[]`, or `[:]`) instructs the `DataStack` to use the .xcdatamodel's current version as the final version, and to disable progressive migrations:
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```
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let dataStack = DataStack(migrationChain: nil)
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```
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This means that the mapping model will be computed from the store's version straight to the `DataStack`'s model version.
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To support progressive migrations, specify the linear order of versions:
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```
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let dataStack = DataStack(migrationChain:
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["MyAppModel", "MyAppModelV2", "MyAppModelV3", "MyAppModelV4"])
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```
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or for more complex migration paths, a version tree that maps the key-values to the source-destination versions:
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```
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let dataStack = DataStack(migrationChain: [
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"MyAppModel": "MyAppModelV3",
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"MyAppModelV2": "MyAppModelV4",
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"MyAppModelV3": "MyAppModelV4"
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])
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```
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This allows for different migration paths depending on the starting version. The example above resolves to the following paths:
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- MyAppModel-MyAppModelV3-MyAppModelV4
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- MyAppModelV2-MyAppModelV4
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- MyAppModelV3-MyAppModelV4
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The `MigrationChain` is validated when passed to the `DataStack` and unless it is empty, will raise an assertion if any of the following conditions are met:
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- a version appears twice in an array
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- a version appears twice as a key in a dictionary literal
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- a loop is found in any of the paths
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*/
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public struct MigrationChain: NilLiteralConvertible, StringLiteralConvertible, DictionaryLiteralConvertible, ArrayLiteralConvertible, Equatable {
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/**
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Initializes the `MigrationChain` with empty values, which instructs the `DataStack` to use the .xcdatamodel's current version as the final version, and to disable progressive migrations.
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*/
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public init() {
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self.versionTree = [:]
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self.rootVersions = []
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self.leafVersions = []
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self.valid = true
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}
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/**
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Initializes the `MigrationChain` with a single model version, which instructs the `DataStack` to use the the specified version as the final version, and to disable progressive migrations.
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*/
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public init(_ value: String) {
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self.versionTree = [:]
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self.rootVersions = [value]
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self.leafVersions = [value]
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self.valid = true
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}
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/**
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Initializes the `MigrationChain` with a linear order of versions, which becomes the order of the `DataStack`'s progressive migrations.
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*/
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public init<T: CollectionType where T.Generator.Element == String, T.Index: BidirectionalIndexType>(_ elements: T) {
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CoreStore.assert(Set(elements).count == Array(elements).count, "\(cs_typeName(MigrationChain))'s migration chain could not be created due to duplicate version strings.")
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var lastVersion: String?
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var versionTree = [String: String]()
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var valid = true
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for version in elements {
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if let lastVersion = lastVersion,
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let _ = versionTree.updateValue(version, forKey: lastVersion) {
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valid = false
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}
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lastVersion = version
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}
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self.versionTree = versionTree
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self.rootVersions = Set([elements.first].flatMap { $0 == nil ? [] : [$0!] })
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self.leafVersions = Set([elements.last].flatMap { $0 == nil ? [] : [$0!] })
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self.valid = valid
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}
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/**
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Initializes the `MigrationChain` with a version tree, which becomes the order of the `DataStack`'s progressive migrations.
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*/
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public init(_ elements: [(String, String)]) {
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var valid = true
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var versionTree = [String: String]()
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elements.forEach { (sourceVersion, destinationVersion) in
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guard let _ = versionTree.updateValue(destinationVersion, forKey: sourceVersion) else {
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return
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}
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CoreStore.assert(false, "\(cs_typeName(MigrationChain))'s migration chain could not be created due to ambiguous version paths.")
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valid = false
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}
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let leafVersions = Set(
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elements
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.filter { versionTree[$1] == nil }
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.map { $1 }
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)
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let isVersionAmbiguous = { (start: String) -> Bool in
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var checklist: Set<String> = [start]
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var version = start
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while let nextVersion = versionTree[version] where nextVersion != version {
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if checklist.contains(nextVersion) {
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CoreStore.assert(false, "\(cs_typeName(MigrationChain))'s migration chain could not be created due to looping version paths.")
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return true
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}
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checklist.insert(nextVersion)
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version = nextVersion
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}
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return false
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}
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self.versionTree = versionTree
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self.rootVersions = Set(versionTree.keys).subtract(versionTree.values)
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self.leafVersions = leafVersions
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self.valid = valid && Set(versionTree.keys).union(versionTree.values).filter { isVersionAmbiguous($0) }.count <= 0
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}
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/**
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Initializes the `MigrationChain` with a version tree, which becomes the order of the `DataStack`'s progressive migrations.
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*/
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public init(_ dictionary: [String: String]) {
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self.init(dictionary.map { $0 })
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}
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// MARK: NilLiteralConvertible
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public init(nilLiteral: ()) {
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self.init()
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}
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// MARK: StringLiteralConvertible
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public init(stringLiteral value: String) {
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self.init(value)
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}
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// MARK: ExtendedGraphemeClusterLiteralConvertible
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public init(extendedGraphemeClusterLiteral value: String) {
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self.init(value)
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}
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// MARK: UnicodeScalarLiteralConvertible
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public init(unicodeScalarLiteral value: String) {
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self.init(value)
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}
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// MARK: DictionaryLiteralConvertible
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public init(dictionaryLiteral elements: (String, String)...) {
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self.init(elements)
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}
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// MARK: ArrayLiteralConvertible
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public init(arrayLiteral elements: String...) {
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self.init(elements)
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}
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// MARK: Internal
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internal let rootVersions: Set<String>
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internal let leafVersions: Set<String>
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internal let valid: Bool
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internal var empty: Bool {
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return self.versionTree.count <= 0
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}
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internal func contains(version: String) -> Bool {
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return self.rootVersions.contains(version)
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|| self.leafVersions.contains(version)
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|| self.versionTree[version] != nil
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}
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internal func nextVersionFrom(version: String) -> String? {
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guard let nextVersion = self.versionTree[version] where nextVersion != version else {
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return nil
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}
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return nextVersion
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}
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// MARK: Private
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private let versionTree: [String: String]
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}
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// MARK: - MigrationChain: Equatable
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@warn_unused_result
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public func == (lhs: MigrationChain, rhs: MigrationChain) -> Bool {
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return lhs.versionTree == rhs.versionTree
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&& lhs.rootVersions == rhs.rootVersions
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&& lhs.leafVersions == rhs.leafVersions
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&& lhs.valid == rhs.valid
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}
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