Add diagnostics to use module aliasing when duplicate targets found (#5607)

Resolves rdar://93218209

Author: elsh

Sources/PackageLoading/PackageBuilder.swift

@@ -83,7 +83,7 @@ extension ModuleError: CustomStringConvertible {
         switch self {
         case .duplicateModule(let name, let packages):
             let packages = packages.joined(separator: "', '")
-            return "multiple targets named '\(name)' in: '\(packages)'"
+            return "multiple targets named '\(name)' in: '\(packages)'; consider using the `moduleAliases` parameter in manifest to provide unique names"
         case .moduleNotFound(let target, let type):
             let folderName = (type == .test) ? "Tests" : (type == .plugin) ? "Plugins" : "Sources"
             return "Source files for target \(target) should be located under '\(folderName)/\(target)', or a custom sources path can be set with the 'path' property in Package.swift"

Tests/PackageGraphTests/PackageGraphTests.swift

@@ -291,7 +291,7 @@ class PackageGraphTests: XCTestCase {
         )
 
         testDiagnostics(observability.diagnostics) { result in
-            result.check(diagnostic: "multiple targets named 'Bar' in: 'bar', 'foo'", severity: .error)
+            result.check(diagnostic: "multiple targets named 'Bar' in: 'bar', 'foo'; consider using the `moduleAliases` parameter in manifest to provide unique names", severity: .error)
         }
     }
 
@@ -350,7 +350,7 @@ class PackageGraphTests: XCTestCase {
         )
 
         testDiagnostics(observability.diagnostics) { result in
-            result.check(diagnostic: "multiple targets named 'First' in: 'first', 'fourth', 'second', 'third'", severity: .error)
+            result.check(diagnostic: "multiple targets named 'First' in: 'first', 'fourth', 'second', 'third'; consider using the `moduleAliases` parameter in manifest to provide unique names", severity: .error)
         }
     }
 
@@ -409,8 +409,8 @@ class PackageGraphTests: XCTestCase {
         )
 
         testDiagnostics(observability.diagnostics) { result in
-            result.check(diagnostic: "multiple targets named 'Bar' in: 'fourth', 'third'", severity: .error)
-            result.check(diagnostic: "multiple targets named 'Foo' in: 'first', 'second'", severity: .error)
+            result.check(diagnostic: "multiple targets named 'Bar' in: 'fourth', 'third'; consider using the `moduleAliases` parameter in manifest to provide unique names", severity: .error)
+            result.check(diagnostic: "multiple targets named 'Foo' in: 'first', 'second'; consider using the `moduleAliases` parameter in manifest to provide unique names", severity: .error)
         }
     }
 
@@ -476,7 +476,7 @@ class PackageGraphTests: XCTestCase {
         )
 
         testDiagnostics(observability.diagnostics) { result in
-            result.check(diagnostic: "multiple targets named 'First' in: 'first', 'fourth'", severity: .error)
+            result.check(diagnostic: "multiple targets named 'First' in: 'first', 'fourth'; consider using the `moduleAliases` parameter in manifest to provide unique names", severity: .error)
         }
     }
 
@@ -950,7 +950,7 @@ class PackageGraphTests: XCTestCase {
         )
 
         testDiagnostics(observability.diagnostics) { result in
-            result.check(diagnostic: "multiple targets named 'Foo' in: 'dep2', 'start'", severity: .error)
+            result.check(diagnostic: "multiple targets named 'Foo' in: 'dep2', 'start'; consider using the `moduleAliases` parameter in manifest to provide unique names", severity: .error)
         }
     }