feat: validation specific usage gen error message (#1091)

internal/usagegen/usagegen.go

@@ -4,14 +4,15 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"github.com/speakeasy-api/sdk-gen-config/workflow"
-	"github.com/speakeasy-api/speakeasy-core/openapi"
 	"io/fs"
 	"os"
 	"regexp"
 	"sort"
 	"strings"
 
+	"github.com/speakeasy-api/sdk-gen-config/workflow"
+	"github.com/speakeasy-api/speakeasy-core/openapi"
+
 	"github.com/speakeasy-api/speakeasy/internal/utils"
 
 	"github.com/pkg/errors"
@@ -69,10 +70,18 @@ func Generate(ctx context.Context, customerID, lang, schemaPath, header, token,
 	}
 
 	if errs := g.Generate(ctx, schema, schemaPath, lang, configPath, isRemote, false); len(errs) > 0 {
+		isValidationError := false
 		for _, err := range errs {
+			if strings.Contains(err.Error(), "validation error:") {
+				isValidationError = true
+			}
 			l.Error("", zap.Error(err))
 		}
 
+		if isValidationError {
+			return fmt.Errorf("failed to generate usage snippets: the provided openapi spec is not valid for sdk generation")
+		}
+
 		return fmt.Errorf("failed to generate usage snippets for %s ✖", lang)
 	}