Whole tree builds (#308)

changes SSGC’s compilation model so that it now compiles the full dependency tree for one module at a time, instead of a partial set of dependencies for the entire package

Author: tayloraswift

Package.resolved

@@ -92,7 +92,7 @@ let package:Package = .init(
         .package(url: "https://github.com/tayloraswift/swift-hash", .upToNextMinor(
             from: "0.6.0")),
         .package(url: "https://github.com/tayloraswift/swift-mongodb", .upToNextMinor(
-            from: "0.23.0")),
+            from: "0.23.1")),
         .package(url: "https://github.com/tayloraswift/swift-unixtime", .upToNextMinor(
             from: "0.1.0")),
 
@@ -103,7 +103,7 @@ let package:Package = .init(
             from: "4.4.3")),
 
         .package(url: "https://github.com/apple/swift-argument-parser", .upToNextMinor(
-            from: "1.4.0")),
+            from: "1.5.0")),
         .package(url: "https://github.com/apple/swift-atomics", .upToNextMinor(
             from: "1.2.0")),
         .package(url: "https://github.com/apple/swift-collections", .upToNextMinor(
@@ -303,11 +303,13 @@ let package:Package = .init(
         .target(name: "PackageGraphs",
             dependencies: [
                 .target(name: "SymbolGraphs"),
+                .target(name: "TopologicalSorting"),
             ]),
 
         .target(name: "PackageMetadata",
             dependencies: [
                 .target(name: "PackageGraphs"),
+                .product(name: "OrderedCollections", package: "swift-collections"),
                 .product(name: "JSON", package: "swift-json"),
             ]),
 
@@ -431,6 +433,8 @@ let package:Package = .init(
                 .product(name: "Testing_", package: "swift-grammar"),
             ]),
 
+        .target(name: "TopologicalSorting"),
+
         .target(name: "UA",
             dependencies: [
                 .product(name: "Grammar", package: "swift-grammar"),
@@ -642,8 +646,7 @@ let package:Package = .init(
 
         .executableTarget(name: "SymbolGraphCompilerTests",
             dependencies: [
-                .target(name: "SymbolGraphCompiler"),
-                .target(name: "System"),
+                .target(name: "SymbolGraphBuilder"),
                 .product(name: "Testing_", package: "swift-grammar"),
             ]),
 
@@ -684,6 +687,12 @@ let package:Package = .init(
                 "directories",
             ]),
 
+        .executableTarget(name: "TopologicalSortingTests",
+            dependencies: [
+                .target(name: "TopologicalSorting"),
+                .product(name: "Testing_", package: "swift-grammar"),
+            ]),
+
         .executableTarget(name: "UATests",
             dependencies: [
                 .target(name: "UA"),

Package.swift

@@ -44,12 +44,11 @@ extension AsyncSequence where Element:Sendable
     func iterate(concurrently width:Int,
         with body:@Sendable @escaping (Element) async -> ()) async throws
     {
+        var iterator:AsyncIterator = self.makeAsyncIterator()
         let exit:Result<Void, any Error> = await withTaskGroup(of: Void.self)
         {
             (tasks:inout TaskGroup<Void>) in
 
-            var iterator:AsyncIterator = self.makeAsyncIterator()
-
             do
             {
                 for _:Int in 0 ..< width

Sources/HTTPServer/AsyncSequence (ext).swift

@@ -1,6 +1,6 @@
 /// At least one dependency cycle exists in the relevant digraph.
 public
-struct DigraphCycleError<Node>:Error, Equatable, Sendable where Node:DigraphNode
+struct DigraphCycleError<Node>:Error, Equatable, Sendable where Node:Identifiable
 {
     public
     init()

Sources/PackageGraphs/Digraphs/DigraphCycleError.swift

@@ -45,8 +45,8 @@ extension DigraphExplorer.Nodes
 }
 extension DigraphExplorer<TargetNode>.Nodes
 {
-    public
-    init(indexing nodes:[TargetNode]) throws
+    @inlinable public
+    init(indexing nodes:some Sequence<TargetNode>) throws
     {
         self.init()
         for node:TargetNode in nodes

Sources/PackageGraphs/Digraphs/DigraphExplorer.Nodes.swift

@@ -1,6 +1,6 @@
 /// Context for a breadth-first traversal of a digraph.
 @frozen public
-struct DigraphExplorer<Node> where Node:DigraphNode, Node.ID:Sendable
+struct DigraphExplorer<Node> where Node:Identifiable, Node.ID:Sendable
 {
     @usableFromInline internal
     let nodes:Nodes

Sources/PackageGraphs/Digraphs/DigraphExplorer.swift

@@ -1,5 +1,5 @@
 public
-enum DigraphNodeError<Node>:Error, Equatable where Node:DigraphNode, Node.ID:Sendable
+enum DigraphNodeError<Node>:Error, Equatable where Node:Identifiable, Node.ID:Sendable
 {
     case duplicate(Node.ID)
     case undefined(Node.ID)

Sources/PackageGraphs/Digraphs/DigraphNode.swift

@@ -1,5 +1,6 @@
 import SymbolGraphs
 import Symbols
+import TopologicalSorting
 
 /// A package node is a flattened representation of a package manifest.
 /// Creating one involves assigning an identity to a package manifest
@@ -12,9 +13,6 @@ struct PackageNode:Identifiable
     public
     var dependencies:[any Identifiable<Symbol.Package>]
 
-    public
-    var snippets:String
-
     public
     var products:[SymbolGraph.Product]
     public
@@ -28,26 +26,19 @@ struct PackageNode:Identifiable
     @inlinable public
     init(id:Symbol.Package,
         dependencies:[any Identifiable<Symbol.Package>],
-        snippets:String = "Snippets",
         products:[SymbolGraph.Product],
         modules:[SymbolGraph.Module],
         exclude:[[String]],
         root:Symbol.FileBase)
     {
         self.id = id
         self.dependencies = dependencies
-        self.snippets = snippets
         self.products = products
         self.modules = modules
         self.exclude = exclude
         self.root = root
     }
 }
-extension PackageNode:DigraphNode
-{
-    @inlinable public
-    var predecessors:Predecessors { .init(self.dependencies) }
-}
 extension PackageNode
 {
     public consuming
@@ -98,7 +89,24 @@ extension PackageNode
             }
         }
 
-        self.dependencies = try Self.order(topologically: dependencies).compactMap
+        let directedEdges:[(Symbol.Package, Symbol.Package)] = dependencies.reduce(into: [])
+        {
+            for dependency:any Identifiable<Symbol.Package> in $1.dependencies
+            {
+                $0.append((dependency.id, $1.id))
+            }
+        }
+
+        //  FIXME: in Swift 6, it will be legal to have cyclic package dependencies!
+        guard
+        let dependenciesOrdered:[PackageNode] = dependencies.sortedTopologically(
+            by: directedEdges)
+        else
+        {
+            throw DigraphCycleError<PackageNode>.init()
+        }
+
+        self.dependencies = dependenciesOrdered.compactMap
         {
             actuallyUsed.contains($0.id)
                 ? declared[$0.id] ?? TransitiveDependency.init(id: $0.id)