Duplicate error message on package resolved (#3258)

motivation: fix a bug where in some cases a duplicate error message is printed

changes: only try to load the graph if the previous operation succeeded

Author: tomerd

Sources/Commands/SwiftPackageTool.swift

@@ -133,17 +133,19 @@ extension SwiftPackageTool {
                 dryRun: dryRun
             )
 
-            if let pinsStore = swiftTool.diagnostics.wrap({ try workspace.pinsStore.load() }), let changes = changes, dryRun {
-                logPackageChanges(changes: changes, pins: pinsStore)
-            }
-
-            if !dryRun {
-                // try to load the graph which will emit any errors
+            // try to load the graph which will emit any errors
+            if !swiftTool.diagnostics.hasErrors {
                 _ = try workspace.loadPackageGraph(
                     rootInput: swiftTool.getWorkspaceRoot(),
                     diagnostics: swiftTool.diagnostics
                 )
+            }
 
+            if let pinsStore = swiftTool.diagnostics.wrap({ try workspace.pinsStore.load() }), let changes = changes, dryRun {
+                logPackageChanges(changes: changes, pins: pinsStore)
+            }
+
+            if !dryRun {
                 // Throw if there were errors when loading the graph.
                 // The actual errors will be printed before exiting.
                 guard !swiftTool.diagnostics.hasErrors else {