[kotlin] Fix empty body with POST/etc in OkHttp client (#13666)

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache

@@ -343,7 +343,7 @@ import com.squareup.moshi.adapter
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -351,16 +351,16 @@ import com.squareup.moshi.adapter
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -158,7 +158,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -166,16 +166,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-array-simple-string-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -156,7 +156,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -164,16 +164,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -158,7 +158,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -166,16 +166,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -158,7 +158,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -166,16 +166,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-default-values-jvm-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -156,7 +156,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -164,16 +164,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -158,7 +158,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -166,16 +166,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -158,7 +158,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -166,16 +166,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -176,7 +176,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -184,16 +184,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -176,7 +176,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -184,16 +184,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -182,7 +182,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -190,16 +190,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -179,7 +179,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -187,16 +187,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -177,7 +177,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -185,16 +185,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -177,7 +177,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -185,16 +185,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -177,7 +177,7 @@ internal open class ApiClient(val baseUrl: String, val client: OkHttpClient = de
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -185,16 +185,16 @@ internal open class ApiClient(val baseUrl: String, val client: OkHttpClient = de
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -177,7 +177,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -185,16 +185,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-okhttp3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -175,7 +175,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -183,16 +183,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -177,7 +177,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -185,16 +185,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -177,7 +177,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -185,16 +185,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -158,7 +158,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -166,16 +166,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))

samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -177,7 +177,7 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
             }.build()
 
         // take content-type/accept from spec or set to default (application/json) if not defined
-        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+        if (requestConfig.body != null && requestConfig.headers[ContentType].isNullOrEmpty()) {
             requestConfig.headers[ContentType] = JsonMediaType
         }
         if (requestConfig.headers[Accept].isNullOrEmpty()) {
@@ -185,16 +185,16 @@ open class ApiClient(val baseUrl: String, val client: OkHttpClient = defaultClie
         }
         val headers = requestConfig.headers
 
-        if(headers[ContentType].isNullOrEmpty()) {
-            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
-        }
-
-        if(headers[Accept].isNullOrEmpty()) {
+        if (headers[Accept].isNullOrEmpty()) {
             throw kotlin.IllegalStateException("Missing Accept header. This is required.")
         }
 
-        // TODO: support multiple contentType options here.
-        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        val contentType = if (headers[ContentType] != null) {
+            // TODO: support multiple contentType options here.
+            (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+        } else {
+            null
+        }
 
         val request = when (requestConfig.method) {
             RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))