generator: handle Style/Explode values for Query parameters.

README.md

@@ -182,10 +182,11 @@ type MyHandlerParams struct {
 You can use additional tags. Some will be interpreted by *tonic*, others will be exclusively used to enrich the *OpenAPI* specification.
 - `default`: *tonic* will bind this value if none was passed with the request. This should not be used if a field is also required. Read the [documentation](https://swagger.io/docs/specification/describing-parameters/) (section _Common Mistakes_) for more informations about this behaviour.
 - `description`: Add a description of the field in the spec.
-- `deprecated`: Indicates if the field is deprecated. accepted values are _1_, _t_, _T_, _TRUE_, _true_, _True_, _0_, _f_, _F_, _FALSE_. Invalid value are considered to be false.
+- `deprecated`: Indicates if the field is deprecated. Accepted values are _1_, _t_, _T_, _TRUE_, _true_, _True_, _0_, _f_, _F_, _FALSE_. Invalid value are considered to be false.
 - `enum`: A coma separated list of acceptable values for the parameter.
 - `format`: Override the format of the field in the specification. Read the [documentation](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#dataTypeFormat) for more informations.
 - `validate`: Field validation rules. Read the [documentation](https://godoc.org/gopkg.in/go-playground/validator.v8) for more informations.
+- `explode`: Specifies whether arrays should generate separate parameters for each array item or object property (limited to query parameters with *form* style). Accepted values are _1_, _t_, _T_, _TRUE_, _true_, _True_, _0_, _f_, _F_, _FALSE_. Invalid value are considered to be false.
 
 ### JSON/XML
 
@@ -244,7 +245,8 @@ The names of the components can be customized in two different ways.
 
 Override the name of a type globally before registering your handlers. This has the highest precedence.
 ```go
-fizz.Generator().OverrideTypeName(reflect.TypeOf(T{}), "OverridedName")
+f := fizz.New()
+f.Generator().OverrideTypeName(reflect.TypeOf(T{}), "OverridedName")
 ```
 
 ##### Interface

openapi/generator.go

@@ -22,6 +22,11 @@ const (
 	descriptionTag = "description"
 )
 
+var (
+	paramsInPathRe = regexp.MustCompile(`\{(.*?)\}`)
+	ginPathParamRe = regexp.MustCompile(`\/:([^\/]*)`)
+)
+
 // mediaTags maps media types to well-known
 // struct tags used for marshaling.
 var mediaTags = map[string]string{
@@ -281,8 +286,6 @@ func (g *Generator) AddOperation(path, method, tag string, in, out reflect.Type,
 	return nil
 }
 
-var ginPathParamRe = regexp.MustCompile(`\/:([^\/]*)`)
-
 // rewritePath converts a Gin operation path that use
 // colons and asterisks to declare path parameters, to
 // an OpenAPI representation that use curly braces.
@@ -386,8 +389,6 @@ func (g *Generator) setOperationResponse(op *Operation, t reflect.Type, code, mt
 	return nil
 }
 
-var paramsInPathRe = regexp.MustCompile(`\{(.*?)\}`)
-
 // setOperationParams adds the fields of the struct type t
 // to the given operation.
 func (g *Generator) setOperationParams(op *Operation, t, parent reflect.Type, allowBody bool, path string) error {
@@ -603,7 +604,7 @@ func (g *Generator) newParameterFromField(idx int, t reflect.Type) (*Parameter,
 	}
 	required := g.isStructFieldRequired(field)
 
-	// Path parameters are aways required.
+	// Path parameters are always required.
 	if location == g.config.PathLocationTag {
 		required = true
 	}
@@ -621,6 +622,18 @@ func (g *Generator) newParameterFromField(idx int, t reflect.Type) (*Parameter,
 	if field.Type.Kind() == reflect.Bool && location == g.config.QueryLocationTag {
 		p.AllowEmptyValue = true
 	}
+	// Style.
+	if location == g.config.QueryLocationTag {
+		if field.Type.Kind() == reflect.Slice || field.Type.Kind() == reflect.Array {
+			p.Explode = true // default
+			p.Style = "form" // default in spec, but make it obvious
+			if t := field.Tag.Get(tonic.ExplodeTag); t != "" {
+				if explode, err := strconv.ParseBool(t); err == nil && !explode { // ignore invalid values
+					p.Explode = explode
+				}
+			}
+		}
+	}
 	return p, nil
 }
 
@@ -820,8 +833,7 @@ func (g *Generator) buildSchemaRecursive(t reflect.Type) *SchemaOrRef {
 		// in additional properties field.
 		schema.Type = "object"
 
-		// JSON Schema allow only strings as
-		// object key.
+		// JSON Schema allow only strings as object key.
 		if t.Key().Kind() != reflect.String {
 			g.error(&TypeError{
 				Message: "encountered type Map with keys of unsupported type",

openapi/spec.go

@@ -99,6 +99,8 @@ type Parameter struct {
 	Deprecated      bool         `json:"deprecated,omitempty" yaml:"deprecated,omitempty"`
 	AllowEmptyValue bool         `json:"allowEmptyValue,omitempty" yaml:"allowEmptyValue,omitempty"`
 	Schema          *SchemaOrRef `json:"schema,omitempty" yaml:"schema,omitempty"`
+	Style           string       `json:"style,omitempty" yaml:"style,omitempty"`
+	Explode         bool         `json:"explode,omitempty" yaml:"explode,omitempty"`
 }
 
 // ParameterOrRef represents a Parameter that can be inlined

testdata/schemas/path-item.json

@@ -68,7 +68,9 @@
                             "ccc"
                         ]
                     }
-                }
+                },
+                "explode": true,
+                "style": "form"
             },
             {
                 "name": "xd",