fix(minor): Make CI fail for invalid arguments or failed benchmark bu…

…ilds (#210)

Currently a failed build would silently return 0, so CI would be unable to detect such errors.

This PR makes sure that the command plugin will throw errors on any invalid input or for failed builds.

Plugins/BenchmarkCommandPlugin/BenchmarkCommandPlugin.swift

@@ -73,7 +73,7 @@ import PackagePlugin
             print("")
             print("Please visit https://github.com/ordo-one/package-benchmark for more in-depth documentation")
             print("")
-            return
+            throw MyError.invalidArgument
         }
 
         if pathSpecified.count > 0 {
@@ -88,7 +88,7 @@ import PackagePlugin
                 outputFormat = format
             } else {
                 print("Unknown output format '\(outputFormats.first!)'")
-                return
+                throw MyError.invalidArgument
             }
             if outputFormats.count > 1 {
                 print("Only a single output format may be specified, will use the first one specified '\(outputFormat)'")
@@ -100,7 +100,7 @@ import PackagePlugin
                 grouping = group.rawValue
             } else {
                 print("Unknown grouping '\(groupingToUse.first!)', valid groupings are 'metric' and 'benchmark'")
-                return
+                throw MyError.invalidArgument
             }
             if groupingToUse.count > 1 {
                 print("Only a single grouping may be specified, will use the first one specified '\(grouping)'")
@@ -113,14 +113,14 @@ import PackagePlugin
             guard positionalArguments.count == 1 else {
                 print("Must specify exactly one benchmark target name to create, e.g.:")
                 print("swift package --allow-writing-to-package-directory benchmark init MyBenchmarkName")
-                return
+                throw MyError.invalidArgument
             }
             targetName = positionalArguments.removeFirst()
             do {
                 let targets = try context.package.targets(named: [targetName])
                 if targets.isEmpty == false {
                     print("Can't create benchmark executable target named \(targetName), a target with that name already exists.")
-                    return
+                    throw MyError.invalidArgument
                 }
             } catch { // We will throw if we can use the target name (it's unused!)
             }
@@ -158,7 +158,7 @@ import PackagePlugin
         if checkAbsoluteThresholds > 0 {
             if checkAbsoluteThresholdsPath.count > 1 {
                 print("Only a single path for thresholds can be specified, got \(checkAbsoluteThresholdsPath.count).")
-                return
+                throw MyError.invalidArgument
             }
             args.append(contentsOf: ["--check-absolute"])
             if let path = checkAbsoluteThresholdsPath.first {
@@ -189,7 +189,7 @@ import PackagePlugin
 
         if commandToPerform == .run, positionalArguments.count > 0 {
             print("Can't specify baselines for normal run operation, superfluous arguments [\(positionalArguments)]")
-            return
+            throw MyError.invalidArgument
         }
 
         if commandToPerform == .baseline {
@@ -202,7 +202,7 @@ import PackagePlugin
                 print("")
                 print("Please visit https://github.com/ordo-one/package-benchmark for more in-depth documentation")
                 print("")
-                return
+                throw MyError.invalidArgument
             }
 
             args.append(contentsOf: ["--baseline-operation", baselineOperation.rawValue])
@@ -212,7 +212,7 @@ import PackagePlugin
             case .update:
                 guard positionalArguments.count == 1 else {
                     print("A single baseline must be specified for update operations, got: \(positionalArguments)")
-                    return
+                    throw MyError.invalidArgument
                 }
             case .compare:
                 fallthrough
@@ -295,7 +295,7 @@ import PackagePlugin
                 guard buildResult.succeeded else {
                     print(buildResult.logText)
                     print("Benchmark failed to run due to build error.")
-                    return
+                    throw MyError.buildFailed
                 }
 
                 // Filter out all executable products which are Benchmarks we should run
@@ -378,5 +378,6 @@ import PackagePlugin
         case benchmarkUnexpectedReturnCode
         case baselineNotFound
         case invalidArgument
+        case buildFailed
     }
 }