adds traits to dependency output in show-dependencies --json and --text (swiftlang#9034)

Adds traits to the output of the show-dependencies command for `--text`
and `--json` output.

### Motivation:

Exposes the default traits, if any, that are enabled by the dependencies
a package.

Resolves: swiftlang#9033 

### Modifications:

Extended the logic in show-dependencies to add in the `enabledTraits`
for a resolved package.

### Result:

The output of show-dependencies includes output akin to `(traits:
FirstTrait, SecondTrait)` is the resolved package has traits and
includes the traits that it has. If the package doesn't offer traits, no
additional/new content is displayed in `--text`.
The JSON provided from `show-dependencies --json` includes a `traits`
property, empty if there aren't any traits enabled.

Author: heckj

Sources/Commands/Utilities/DependenciesSerializer.swift

@@ -34,7 +34,14 @@ final class PlainTextDumper: DependenciesDumper {
 
                 let pkgVersion = package.manifest.version?.description ?? "unspecified"
 
-                stream.send("\(hanger)\(package.identity.description)<\(package.manifest.packageLocation)@\(pkgVersion)>\n")
+                let traitsEnabled: String
+                if let enabled = package.enabledTraits, !enabled.isEmpty {
+                    traitsEnabled = "(traits: \(package.enabledTraits?.joined(separator: ", ") ?? ""))"
+                } else {
+                    traitsEnabled = ""
+                }
+
+                stream.send("\(hanger)\(package.identity.description)<\(package.manifest.packageLocation)@\(pkgVersion)>\(traitsEnabled)\n")
 
                 if !package.dependencies.isEmpty {
                     let replacement = (index == packages.count - 1) ?  "    " : "│   "
@@ -130,6 +137,7 @@ final class JSONDumper: DependenciesDumper {
                 "url": .string(package.manifest.packageLocation),
                 "version": .string(package.manifest.version?.description ?? "unspecified"),
                 "path": .string(package.path.pathString),
+                "traits": .array(package.enabledTraits?.map { .string($0) } ?? []),
                 "dependencies": .array(package.dependencies.compactMap { graph.packages[$0] }.map(convert)),
             ])
         }

Tests/CommandsTests/PackageCommandTests.swift

@@ -1315,6 +1315,55 @@ struct PackageCommandTests {
             }
         }
 
+        @Test(
+            .tags(
+                .Feature.Command.Package.ShowDependencies,
+            ),
+            arguments: getBuildData(for: SupportedBuildSystemOnAllPlatforms),
+        )
+        func showDependenciesWithTraits(
+            data: BuildData,
+        ) async throws {
+            try await fixture(name: "Traits") { fixturePath in
+                let packageRoot = fixturePath.appending("Example")
+                let (textOutput, _) = try await execute(
+                    ["show-dependencies", "--format=text"],
+                    packagePath: packageRoot,
+                    configuration: data.config,
+                    buildSystem: data.buildSystem,
+                )
+                #expect(textOutput.contains("(traits: Package3Trait3)"))
+
+                let (jsonOutput, _) = try await execute(
+                    ["show-dependencies", "--format=json"],
+                    packagePath: packageRoot,
+                    configuration: data.config,
+                    buildSystem: data.buildSystem,
+                )
+                let json = try JSON(bytes: ByteString(encodingAsUTF8: jsonOutput))
+                guard case .dictionary(let contents) = json else {
+                    Issue.record("unexpected result")
+                    return
+                }
+                guard case .string(let name)? = contents["name"] else {
+                    Issue.record("unexpected result")
+                    return
+                }
+                #expect(name == "TraitsExample")
+
+                // verify the traits JSON entry lists each of the traits in the fixture
+                guard case .array(let traitsProperty)? = contents["traits"] else {
+                    Issue.record("unexpected result")
+                    return
+                }
+                #expect(traitsProperty.contains(.string("Package1")))
+                #expect(traitsProperty.contains(.string("Package2")))
+                #expect(traitsProperty.contains(.string("Package3")))
+                #expect(traitsProperty.contains(.string("Package4")))
+                #expect(traitsProperty.contains(.string("BuildCondition1")))
+            }
+        }
+
         @Test(
             arguments: getBuildData(for: SupportedBuildSystemOnAllPlatforms),
         )