improve error handling for exclude-platform scenario

Author: savil

internal/devbox/packages.go

@@ -450,18 +450,34 @@ func (d *Devbox) installNixPackagesToStore(ctx context.Context) error {
 			fmt.Fprintf(d.stderr, "%s: ", stepMsg)
 			color.New(color.FgRed).Fprintf(d.stderr, "Fail\n")
 
-			platform := nix.System()
-			return usererr.WithUserMessage(
-				err,
-				"package %s cannot be installed on your platform %s.\n"+
-					"If you know this package is incompatible with %[2]s, then "+
-					"you could run `devbox add %[1]s --exclude-platform %[2]s` and re-try.\n"+
-					"If you think this package should be compatible with %[2]s, then "+
-					"it's possible this particular version is not available yet from the nix registry. "+
-					"You could try `devbox add` with a different version for this package.\n",
-				pkg.Raw,
-				platform,
-			)
+			// Check if the user is installing a package that cannot be installed on their platform.
+			// For example, glibcLocales on MacOS will give the following error:
+			// flake output attribute 'legacyPackages.x86_64-darwin.glibcLocales' is not a derivation or path
+			// This is because glibcLocales is only available on Linux.
+			// The user should try `devbox add` again with `--exclude-platform`
+			errMessage := strings.TrimSpace(err.Error())
+			fmt.Printf("errMessage is %s\n", errMessage)
+			maybePackageSystemCompatibilityError :=
+				strings.Contains(errMessage, "error: flake output attribute") &&
+					strings.Contains(errMessage, "is not a derivation or path")
+
+			if maybePackageSystemCompatibilityError {
+				platform := nix.System()
+				return usererr.WithUserMessage(
+					err,
+					"package %s cannot be installed on your platform %s.\n"+
+						"If you know this package is incompatible with %[2]s, then "+
+						"you could run `devbox add %[1]s --exclude-platform %[2]s` and re-try.\n"+
+						"If you think this package should be compatible with %[2]s, then "+
+						"it's possible this particular version is not available yet from the nix registry. "+
+						"You could try `devbox add` with a different version for this package.\n\n"+
+						"Underlying Error from nix is:",
+					pkg.Raw,
+					platform,
+				)
+			}
+
+			return usererr.WithUserMessage(err, "error installing package %s", pkg.Raw)
 		}
 
 		fmt.Fprintf(d.stderr, "%s: ", stepMsg)