Add fallback for old configuration style

As a means to avoid the breaking changes we introduced in v1.11.0, where
the new-style configuration was made the default, we can tweak our
heuristic for how we work out what configuration is in use by only using
the new-style config if the new `--config` flag is used.

This change in itself is non-breaking, and makes it possible to continue
using the old configuration arguments, as long as you don't provide the
new `--config` flag.

Similar to thoughts in oapi-codegen#629, but does not require a revert.

Closes oapi-codegen#629.

README.md

@@ -695,6 +695,12 @@ output-options:
 Have a look at [`cmd/oapi-codegen/oapi-codegen.go`](https://github.com/deepmap/oapi-codegen/blob/master/cmd/oapi-codegen/oapi-codegen.go#L48) 
 to see all the fields on the configuration structure.
 
+**Note:** the old configuration options, present in pre-1.11.0 releases will work again:
+
+```sh
+oapi-codegen --package=petshop --generate="types,client,server,spec" -alias-types petshop-expanded.yaml
+```
+
 ### Import Mappings
 
 OpenAPI specifications may contain references to other OpenAPI specifications,

cmd/oapi-codegen/oapi-codegen.go

@@ -34,12 +34,13 @@ func errExit(format string, args ...interface{}) {
 }
 
 var (
-	flagOutputFile     string
-	flagConfigFile     string
-	flagOldConfigStyle bool
-	flagOutputConfig   bool
-	flagPrintVersion   bool
-	flagPackageName    string
+	isOldConfigStyle bool
+
+	flagOutputFile   string
+	flagConfigFile   string
+	flagOutputConfig bool
+	flagPrintVersion bool
+	flagPackageName  string
 
 	// The options below are deprecated, and they will be removed in a future
 	// release. Please use the new config file format.
@@ -77,7 +78,6 @@ type oldConfiguration struct {
 
 func main() {
 	flag.StringVar(&flagOutputFile, "o", "", "Where to output generated code, stdout is default")
-	flag.BoolVar(&flagOldConfigStyle, "old-config-style", false, "whether to use the older style config file format")
 	flag.BoolVar(&flagOutputConfig, "output-config", false, "when true, outputs a configuration file for oapi-codegen using current settings")
 	flag.StringVar(&flagConfigFile, "config", "", "a YAML config file that controls oapi-codegen behavior")
 	flag.BoolVar(&flagPrintVersion, "version", false, "when specified, print version and exit")
@@ -113,8 +113,13 @@ func main() {
 		os.Exit(1)
 	}
 
+	// fallback to the old config style if we don't receive the new `--config` flag
+	if flagConfigFile == "" {
+		isOldConfigStyle = true
+	}
+
 	var opts configuration
-	if !flagOldConfigStyle {
+	if !isOldConfigStyle {
 		// We simply read the configuration from disk.
 		if flagConfigFile != "" {
 			buf, err := ioutil.ReadFile(flagConfigFile)
@@ -258,7 +263,7 @@ func updateConfigFromFlags(cfg configuration) (configuration, error) {
 
 	if len(unsupportedFlags) > 0 {
 		return configuration{}, fmt.Errorf("flags %s aren't supported in "+
-			"new config style, please use  -old-config-style or update your configuration ",
+			"new config style, please remove the --config flag or update your configuration ",
 			strings.Join(unsupportedFlags, ", "))
 	}
 

internal/test/client/doc.go

@@ -1,3 +1,3 @@
 package client
 
-//go:generate go run github.com/deepmap/oapi-codegen/cmd/oapi-codegen --old-config-style --package=client -o client.gen.go client.yaml
+//go:generate go run github.com/deepmap/oapi-codegen/cmd/oapi-codegen --package=client -o client.gen.go client.yaml

internal/test/issues/issue-579/gen.go

@@ -1,3 +1,3 @@
 package issue_579
 
-//go:generate go run github.com/deepmap/oapi-codegen/cmd/oapi-codegen --old-config-style --package=issue_579 --generate=types,skip-prune --alias-types -o issue.gen.go spec.yaml
+//go:generate go run github.com/deepmap/oapi-codegen/cmd/oapi-codegen --package=issue_579 --generate=types,skip-prune --alias-types -o issue.gen.go spec.yaml