package api

import (
	"errors"
	"fmt"
)

var ErrAudienceTooLong = errors.New("the API only supports at most one element in the audience")

type OidcToken struct {
	Token string `json:"token"`
}

func (c *Client) OidcToken(jobId string, audience ...string) (*OidcToken, *Response, error) {
	type oidcTokenRequest struct {
		Audience string `json:"audience,omitempty"`
	}

	m := &oidcTokenRequest{}
	switch len(audience) {
	case 0:
	case 1:
		m.Audience = audience[0]
	default:
		// While the spec supports multiple audiences in an Id JWT, our API does
		// not support issuing them.
		// See: https://openid.net/specs/openid-connect-core-1_0.html#IDToken.
		return nil, nil, ErrAudienceTooLong
	}

	u := fmt.Sprintf("jobs/%s/oidc/tokens", jobId)
	req, err := c.newRequest("POST", u, m)
	if err != nil {
		return nil, nil, err
	}

	t := &OidcToken{}
	resp, err := c.doRequest(req, t)
	return t, resp, err
}

package api

import (
	"errors"
	"fmt"
)

var ErrAudienceTooLong = errors.New("the API only supports at most one element in the audience")

type OidcToken struct {
	Token string `json:"token"`
}

func (c *Client) OidcToken(jobId string, audience ...string) (*OidcToken, *Response, error) {
	type oidcTokenRequest struct {
		Audience string `json:"audience"`
	}

	var m *oidcTokenRequest
	switch len(audience) {
	case 0:
		m = nil
	case 1:
		m = &oidcTokenRequest{Audience: audience[0]}
	default:
		// While the spec supports multiple audiences in an Id JWT, our API does
		// not support issuing them.
		// See: https://openid.net/specs/openid-connect-core-1_0.html#IDToken.
		return nil, nil, ErrAudienceTooLong
	}

	u := fmt.Sprintf("jobs/%s/oidc/tokens", jobId)
	req, err := c.newRequest("POST", u, m)
	if err != nil {
		return nil, nil, err
	}

	t := &OidcToken{}
	resp, err := c.doRequest(req, t)
	return t, resp, err
}

--- 
+++ 
@@ -13,15 +13,14 @@
 
 func (c *Client) OidcToken(jobId string, audience ...string) (*OidcToken, *Response, error) {
 	type oidcTokenRequest struct {
-		Audience string `json:"audience"`
+		Audience string `json:"audience,omitempty"`
 	}
 
-	var m *oidcTokenRequest
+	m := &oidcTokenRequest{}
 	switch len(audience) {
 	case 0:
-		m = nil
 	case 1:
-		m = &oidcTokenRequest{Audience: audience[0]}
+		m.Audience = audience[0]
 	default:
 		// While the spec supports multiple audiences in an Id JWT, our API does
 		// not support issuing them.
Fix empty object instead of no body for default audience

The ticket seemed to indicate that if there is no audience specified, then
the request was to have an empty body. However, that leads to a 500 from
the API. Reading the associated plugin show that an empty object is
expected in that case.
