[Build/PackageGraph] Sink fallback logic for macro/plugin/test products and packages identification into ModulesGraph

This is a temporary fix until we can figure out a proper way to
handle situations were all we get is a name of a product or a
target.

Resolves: rdar://129400066

Author: xedin

Sources/Build/BuildOperation.swift

@@ -526,36 +526,22 @@ public final class BuildOperation: PackageStructureDelegate, SPMBuildCore.BuildS
             // FIXME: This is super unfortunate that we might need to load the package graph.
             let graph = try getPackageGraph()
 
-            var product = graph.product(
+            let product = graph.product(
                 for: productName,
                 destination: destination == .host ? .tools : .destination
             )
 
-            var buildParameters = if destination == .host {
-                self.toolsBuildParameters
-            } else {
-                self.productsBuildParameters
-            }
-
-            // It's possible to request a build of a macro or a plugin via `swift build`
-            // which won't have the right destination set because it's impossible to indicate it.
-            //
-            // Same happens with `--test-product` - if one of the test targets directly references
-            // a macro then all if its targets and the product itself become `host`.
-            if product == nil && destination == .target {
-                if let toolsProduct = graph.product(for: productName, destination: .tools),
-                   toolsProduct.type == .macro || toolsProduct.type == .plugin || toolsProduct.type == .test
-                {
-                    product = toolsProduct
-                    buildParameters = self.toolsBuildParameters
-                }
-            }
-
             guard let product else {
                 observabilityScope.emit(error: "no product named '\(productName)'")
                 throw Diagnostics.fatalError
             }
 
+            let buildParameters = if product.buildTriple == .tools {
+                self.toolsBuildParameters
+            } else {
+                self.productsBuildParameters
+            }
+
             // If the product is automatic, we build the main target because automatic products
             // do not produce a binary right now.
             if product.type == .library(.automatic) {
@@ -570,33 +556,22 @@ public final class BuildOperation: PackageStructureDelegate, SPMBuildCore.BuildS
             // FIXME: This is super unfortunate that we might need to load the package graph.
             let graph = try getPackageGraph()
 
-            var target = graph.target(
+            let target = graph.target(
                 for: targetName,
                 destination: destination == .host ? .tools : .destination
             )
 
-            var buildParameters = if destination == .host {
-                self.toolsBuildParameters
-            } else {
-                self.productsBuildParameters
-            }
-
-            // It's possible to request a build of a macro or a plugin via `swift build`
-            // which won't have the right destination because it's impossible to indicate it.
-            if target == nil && destination == .target {
-                if let toolsTarget = graph.target(for: targetName, destination: .tools),
-                   toolsTarget.type == .macro || toolsTarget.type == .plugin
-                {
-                    target = toolsTarget
-                    buildParameters = self.toolsBuildParameters
-                }
-            }
-
             guard let target else {
                 observabilityScope.emit(error: "no target named '\(targetName)'")
                 throw Diagnostics.fatalError
             }
 
+            let buildParameters = if target.buildTriple == .tools {
+                self.toolsBuildParameters
+            } else {
+                self.productsBuildParameters
+            }
+
             return target.getLLBuildTargetName(buildParameters: buildParameters)
         }
     }

Sources/PackageGraph/ModulesGraph.swift

@@ -167,11 +167,57 @@ public struct ModulesGraph {
     }
 
     public func product(for name: String, destination: BuildTriple) -> ResolvedProduct? {
-        self.allProducts.first { $0.name == name && $0.buildTriple == destination }
+        func findProduct(name: String, destination: BuildTriple) -> ResolvedProduct? {
+            self.allProducts.first { $0.name == name && $0.buildTriple == destination }
+        }
+
+        if let product = findProduct(name: name, destination: destination) {
+            return product
+        }
+
+        // FIXME: This is a temporary workaround and needs to be handled by the callers.
+
+        // It's possible to request a build of a macro, a plugin, or a test via `swift build`
+        // which won't have the right destination set because it's impossible to indicate it.
+        //
+        // Same happens with `--test-product` - if one of the test targets directly references
+        // a macro then all if its targets and the product itself become `host`.
+        if destination == .destination {
+            if let toolsProduct = findProduct(name: name, destination: .tools),
+                toolsProduct.type == .macro || toolsProduct.type == .plugin || toolsProduct.type == .test
+            {
+                return toolsProduct
+            }
+        }
+
+        return nil
     }
 
     public func target(for name: String, destination: BuildTriple) -> ResolvedModule? {
-        self.allTargets.first { $0.name == name && $0.buildTriple == destination }
+        func findModule(name: String, destination: BuildTriple) -> ResolvedModule? {
+            self.allTargets.first { $0.name == name && $0.buildTriple == destination }
+        }
+
+        if let module = findModule(name: name, destination: destination) {
+            return module
+        }
+
+        // FIXME: This is a temporary workaround and needs to be handled by the callers.
+
+        // It's possible to request a build of a macro, a plugin or a test via `swift build`
+        // which won't have the right destination set because it's impossible to indicate it.
+        //
+        // Same happens with `--test-product` - if one of the test targets directly references
+        // a macro then all if its targets and the product itself become `host`.
+        if destination == .destination {
+            if let toolsModule = findModule(name: name, destination: .tools),
+                toolsModule.type == .macro || toolsModule.type == .plugin || toolsModule.type == .test
+            {
+                return toolsModule
+            }
+        }
+
+        return nil
     }
 
     /// All root and root dependency packages provided as input to the graph.