Use codegen config in simplify

cmd/gen/simplify/main.go

@@ -5,13 +5,16 @@ import (
 	"fmt"
 	"os"
 
+	"github.com/doordash-oss/oapi-codegen-dd/v3/pkg/codegen"
 	"github.com/mockzilla/connexions/v2/internal/files"
 	"github.com/mockzilla/connexions/v2/pkg/typedef"
 	"github.com/pb33f/libopenapi"
 	"github.com/pb33f/libopenapi/datamodel"
+	"go.yaml.in/yaml/v4"
 )
 
 var (
+	flagConfig                string
 	flagOutput                string
 	flagKeepOptional          int
 	flagMinOptionalProperties int
@@ -29,14 +32,17 @@ func init() {
 		fmt.Fprintf(os.Stderr, "  - Removes optional properties with union types\n")
 		fmt.Fprintf(os.Stderr, "  - Reduces required union properties to single variant (first variant)\n")
 		fmt.Fprintf(os.Stderr, "  - Removes all extension fields (x-*) and examples\n")
-		fmt.Fprintf(os.Stderr, "  - Optionally limits number of optional properties per schema\n\n")
+		fmt.Fprintf(os.Stderr, "  - Optionally limits number of optional properties per schema\n")
+		fmt.Fprintf(os.Stderr, "  - With -config: applies oapi-codegen-dd filter+overlay+prune\n")
+		fmt.Fprintf(os.Stderr, "    BEFORE simplification (filter paths/tags/operation-ids,\n")
+		fmt.Fprintf(os.Stderr, "    apply OpenAPI Overlay 1.0 deltas, drop dangling refs)\n\n")
 		fmt.Fprintf(os.Stderr, "Options:\n")
 		flag.PrintDefaults()
 		fmt.Fprintf(os.Stderr, "\nExamples:\n")
 		fmt.Fprintf(os.Stderr, "  # Simplify unions and keep 5 optional properties per schema (default)\n")
 		fmt.Fprintf(os.Stderr, "  go run %s openapi.yml\n\n", cmdPath)
-		fmt.Fprintf(os.Stderr, "  # Simplify and save to file\n")
-		fmt.Fprintf(os.Stderr, "  go run %s -output simplified.yml openapi.yml\n\n", cmdPath)
+		fmt.Fprintf(os.Stderr, "  # Apply codegen.yml filter+overlay before simplification\n")
+		fmt.Fprintf(os.Stderr, "  go run %s -config codegen.yml -output simplified.yml openapi.yml\n\n", cmdPath)
 		fmt.Fprintf(os.Stderr, "  # Keep exactly 3 optional properties per schema\n")
 		fmt.Fprintf(os.Stderr, "  go run %s -keep-optional 3 openapi.yml\n\n", cmdPath)
 		fmt.Fprintf(os.Stderr, "  # Keep 1-3 optional properties (alphabetically first) per schema\n")
@@ -46,6 +52,7 @@ func init() {
 
 func main() {
 	flag.BoolVar(&flagPrintUsage, "help", false, "Show this help and exit.")
+	flag.StringVar(&flagConfig, "config", "", "Path to oapi-codegen-dd codegen.yml. When set, the spec is run through filter+overlay+prune (using cfg.Filter and cfg.Overlay) before simplification.")
 	flag.StringVar(&flagOutput, "output", "", "Output file path. If not specified, outputs to stdout.")
 	flag.IntVar(&flagKeepOptional, "keep-optional", 5, "Keep exactly this many optional properties per schema. (default 5)")
 	flag.IntVar(&flagMinOptionalProperties, "min-optional-properties", 0, "Minimum number of optional properties to keep (overrides -keep-optional, used with -max-optional-properties).")
@@ -74,13 +81,9 @@ func main() {
 		os.Exit(1)
 	}
 
-	// Create document with config to skip circular reference check
-	docConfig := &datamodel.DocumentConfiguration{
-		SkipCircularReferenceCheck: true,
-	}
-	doc, err := libopenapi.NewDocumentWithConfiguration(specContents, docConfig)
+	doc, err := loadDocument(specContents)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error parsing OpenAPI spec: %v\n", err)
+		fmt.Fprintf(os.Stderr, "Error loading OpenAPI spec: %v\n", err)
 		os.Exit(1)
 	}
 
@@ -127,3 +130,33 @@ func main() {
 		fmt.Print(string(rendered))
 	}
 }
+
+// loadDocument parses the OpenAPI bytes and, when -config is supplied,
+// runs them through oapi-codegen-dd's filter + overlay + prune pipeline
+// before simplification. Without -config it falls back to the historical
+// behaviour: a plain libopenapi document with circular-ref check disabled.
+func loadDocument(specContents []byte) (libopenapi.Document, error) {
+	if flagConfig == "" {
+		docConfig := &datamodel.DocumentConfiguration{
+			SkipCircularReferenceCheck: true,
+		}
+		return libopenapi.NewDocumentWithConfiguration(specContents, docConfig)
+	}
+
+	cfgBytes, err := os.ReadFile(flagConfig)
+	if err != nil {
+		return nil, fmt.Errorf("reading config %q: %w", flagConfig, err)
+	}
+
+	var cfg codegen.Configuration
+	if err := yaml.Unmarshal(cfgBytes, &cfg); err != nil {
+		return nil, fmt.Errorf("parsing config %q: %w", flagConfig, err)
+	}
+	cfg = cfg.WithDefaults()
+
+	// CreateDocument applies overlay (cfg.Overlay) -> filter (cfg.Filter)
+	// -> prune (drops dangling refs). Same pipeline used by `connexions
+	// gen-service`, so users can share one codegen.yml between codegen and
+	// simplify and get the same surface in both.
+	return codegen.CreateDocument(specContents, cfg)
+}