Fix types starting with numbers

Prefix type and variable names for schemas that start with
numbers with an 'N'

internal/test/schemas/schemas.yaml

@@ -37,6 +37,16 @@ paths:
         required: true
         schema:
           type: string
+  /issues/41/{1param}:
+    get:
+      operationId: Issue41
+      description: Parameter name starting with number
+      parameters:
+        - name: 1param
+          in: path
+          required: true
+          schema:
+            $ref: "#/components/schemas/5StartsWithNumber"
 components:
   schemas:
     GenericObject:
@@ -47,3 +57,6 @@ components:
     CustomStringType:
       type: string
       format: custom
+    5StartsWithNumber:
+      type: object
+      description: This schema name starts with a number

pkg/codegen/codegen.go

@@ -279,7 +279,7 @@ func GenerateTypesForSchemas(t *template.Template, schemas map[string]*openapi3.
 
 		types = append(types, TypeDefinition{
 			JsonName: schemaName,
-			TypeName: ToCamelCase(schemaName),
+			TypeName: SchemaNameToTypeName(schemaName),
 			Schema:   goSchema,
 		})
 
@@ -303,7 +303,7 @@ func GenerateTypesForParameters(t *template.Template, params map[string]*openapi
 		typeDef := TypeDefinition{
 			JsonName: paramName,
 			Schema:   goType,
-			TypeName: ToCamelCase(paramName),
+			TypeName: SchemaNameToTypeName(paramName),
 		}
 
 		if paramOrRef.Ref != "" {
@@ -312,7 +312,7 @@ func GenerateTypesForParameters(t *template.Template, params map[string]*openapi
 			if err != nil {
 				return nil, errors.Wrap(err, fmt.Sprintf("error generating Go type for (%s) in parameter %s", paramOrRef.Ref, paramName))
 			}
-			typeDef.TypeName = ToCamelCase(refType)
+			typeDef.TypeName = SchemaNameToTypeName(refType)
 		}
 
 		types = append(types, typeDef)
@@ -342,7 +342,7 @@ func GenerateTypesForResponses(t *template.Template, responses openapi3.Response
 			typeDef := TypeDefinition{
 				JsonName: responseName,
 				Schema:   goType,
-				TypeName: ToCamelCase(responseName),
+				TypeName: SchemaNameToTypeName(responseName),
 			}
 
 			if responseOrRef.Ref != "" {
@@ -351,7 +351,7 @@ func GenerateTypesForResponses(t *template.Template, responses openapi3.Response
 				if err != nil {
 					return nil, errors.Wrap(err, fmt.Sprintf("error generating Go type for (%s) in parameter %s", responseOrRef.Ref, responseName))
 				}
-				typeDef.TypeName = ToCamelCase(refType)
+				typeDef.TypeName = SchemaNameToTypeName(refType)
 			}
 			types = append(types, typeDef)
 		}
@@ -380,7 +380,7 @@ func GenerateTypesForRequestBodies(t *template.Template, bodies map[string]*open
 			typeDef := TypeDefinition{
 				JsonName: bodyName,
 				Schema:   goType,
-				TypeName: ToCamelCase(bodyName),
+				TypeName: SchemaNameToTypeName(bodyName),
 			}
 
 			if bodyOrRef.Ref != "" {
@@ -389,7 +389,7 @@ func GenerateTypesForRequestBodies(t *template.Template, bodies map[string]*open
 				if err != nil {
 					return nil, errors.Wrap(err, fmt.Sprintf("error generating Go type for (%s) in body %s", bodyOrRef.Ref, bodyName))
 				}
-				typeDef.TypeName = ToCamelCase(refType)
+				typeDef.TypeName = SchemaNameToTypeName(refType)
 			}
 			types = append(types, typeDef)
 		}

pkg/codegen/operations.go

@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"strings"
 	"text/template"
+	"unicode"
 
 	"github.com/getkin/kin-openapi/openapi3"
 	"github.com/pkg/errors"
@@ -112,6 +113,9 @@ func (pd ParameterDefinition) GoVariableName() string {
 	if IsGoKeyword(name) {
 		name = "p" + UppercaseFirstCharacter(name)
 	}
+	if unicode.IsNumber([]rune(name)[0]) {
+		name = "n" + name
+	}
 	return name
 }
 

pkg/codegen/schema.go

@@ -59,7 +59,7 @@ type Property struct {
 }
 
 func (p Property) GoFieldName() string {
-	return ToCamelCase(p.JsonFieldName)
+	return SchemaNameToTypeName(p.JsonFieldName)
 }
 
 func (p Property) GoTypeDef() string {

pkg/codegen/utils.go

@@ -201,7 +201,7 @@ func RefPathToGoType(refPath string) (string, error) {
 	if len(pathParts) != 4 {
 		return "", errors.New("Parameter nesting is deeper than supported")
 	}
-	return ToCamelCase(pathParts[3]), nil
+	return SchemaNameToTypeName(pathParts[3]), nil
 }
 
 // This function converts a swagger style path URI with parameters to a
@@ -293,12 +293,15 @@ func IsGoKeyword(str string) bool {
 	return false
 }
 
-// Prefixes a string if it's a go keyword
-func PrefixKeyword(str, prefix string) string {
-	if IsGoKeyword(str) {
-		return prefix + UppercaseFirstCharacter(str)
+// Converts a Schema name to a valid Go type name. It converts to camel case, and makes sure the name is
+// valid in Go
+func SchemaNameToTypeName(name string) string {
+	name = ToCamelCase(name)
+	// Prepend "N" to schemas starting with a number
+	if unicode.IsDigit([]rune(name)[0]) {
+		name = "N" + name
 	}
-	return str
+	return name
 }
 
 // According to the spec, additionalProperties may be true, false, or a