add fallback body to paginator to handle empty responses

ExpediaGroup · Jan 29, 2025 · 24c82e3 · 24c82e3
1 parent 173a5cb
commit 24c82e3
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Showing 4 changed files with 38 additions and 19 deletions.
diff --git a/core/src/main/kotlin/com/expediagroup/sdk/core/model/paging/Paginator.kt b/core/src/main/kotlin/com/expediagroup/sdk/core/model/paging/Paginator.kt
@@ -24,6 +24,7 @@ import io.ktor.client.statement.HttpResponse
 sealed class BasePaginator<R, T>(
     private val client: Client,
     firstResponse: Response<T>,
+    private val fallbackBody: T,
     private val getBody: suspend (HttpResponse) -> T
 ) : Iterator<R> {
     private var state: ResponseState<T> = DefaultResponseState(firstResponse)
@@ -41,7 +42,7 @@ sealed class BasePaginator<R, T>(
 
     protected fun nextResponse(): Response<T> {
         val response = state.getNextResponse()
-        state = ResponseStateFactory.getState(extractLink(response.headers), client, getBody)
+        state = ResponseStateFactory.getState(extractLink(response.headers), client, fallbackBody, getBody)
         return response
     }
 }
@@ -56,8 +57,9 @@ sealed class BasePaginator<R, T>(
 class Paginator<T>(
     client: Client,
     firstResponse: Response<T>,
+    fallbackBody: T,
     getBody: suspend (HttpResponse) -> T
-) : BasePaginator<T, T>(client, firstResponse, getBody) {
+) : BasePaginator<T, T>(client, firstResponse, fallbackBody, getBody) {
     /**
      * Returns the body of the next response.
      *
@@ -76,8 +78,9 @@ class Paginator<T>(
 class ResponsePaginator<T>(
     client: Client,
     firstResponse: Response<T>,
+    fallbackBody: T,
     getBody: suspend (HttpResponse) -> T
-) : BasePaginator<Response<T>, T>(client, firstResponse, getBody) {
+) : BasePaginator<Response<T>, T>(client, firstResponse, fallbackBody, getBody) {
     /**
      * Returns the next response.
      *

diff --git a/core/src/main/kotlin/com/expediagroup/sdk/core/model/paging/ResponseState.kt b/core/src/main/kotlin/com/expediagroup/sdk/core/model/paging/ResponseState.kt
@@ -18,6 +18,7 @@ package com.expediagroup.sdk.core.model.paging
 import com.expediagroup.sdk.core.client.Client
 import com.expediagroup.sdk.core.model.Response
 import io.ktor.client.statement.HttpResponse
+import io.ktor.client.statement.bodyAsBytes
 import kotlinx.coroutines.runBlocking
 
 internal interface ResponseState<T> {
@@ -51,6 +52,7 @@ internal class LastResponseState<T> : ResponseState<T> {
 internal class FetchLinkState<T>(
     private val link: String,
     private val client: Client,
+    private val fallbackBody: T,
     private val getBody: suspend (HttpResponse) -> T
 ) : ResponseState<T> {
     override fun getNextResponse(): Response<T> {
@@ -66,7 +68,9 @@ internal class FetchLinkState<T>(
     }
 
     private suspend fun parseBody(response: HttpResponse): T {
-        return getBody(response)
+        // response.bodyAsBytes() applies all plugins
+        // if content-length header is set, response.contentLength could be used instead
+        return if (response.bodyAsBytes().isEmpty()) fallbackBody else getBody(response)
     }
 }
 
@@ -75,9 +79,10 @@ internal class ResponseStateFactory {
         fun <T> getState(
             link: String?,
             client: Client,
+            fallbackBody: T,
             getBody: suspend (HttpResponse) -> T
         ): ResponseState<T> {
-            return link?.let { FetchLinkState(it, client, getBody) } ?: LastResponseState()
+            return link?.let { FetchLinkState(it, client, fallbackBody, getBody) } ?: LastResponseState()
         }
     }
 }
diff --git a/core/src/test/kotlin/com/expediagroup/sdk/core/model/paging/PaginatorTest.kt b/core/src/test/kotlin/com/expediagroup/sdk/core/model/paging/PaginatorTest.kt
@@ -44,7 +44,7 @@ class PaginatorTest {
         fun `test paginator with one response`() {
             val firstResponse = Response(200, "first", emptyMap())
 
-            val paginator = Paginator(client, firstResponse, getBody)
+            val paginator = Paginator(client, firstResponse, EMPTY_STRING, getBody)
             assertTrue(paginator.hasNext())
             assertEquals("first", paginator.next())
             assertFalse(paginator.hasNext())
@@ -54,7 +54,7 @@ class PaginatorTest {
         fun `test paginator with multiple responses`() {
             val firstResponse = Response(200, "first", mapOf("link" to listOf("<second>; rel=\"next\"")))
 
-            val paginator = Paginator(client, firstResponse, getBody)
+            val paginator = Paginator(client, firstResponse, EMPTY_STRING, getBody)
             assertTrue(paginator.hasNext())
             assertEquals("first", paginator.next())
             assertTrue(paginator.hasNext())
@@ -66,7 +66,7 @@ class PaginatorTest {
         fun `test paginator with multiple responses and total results`() {
             val firstResponse = Response(200, "first", mapOf("link" to listOf("<second>; rel=\"next\""), "pagination-total-results" to listOf("2")))
 
-            val paginator = Paginator(client, firstResponse, getBody)
+            val paginator = Paginator(client, firstResponse, EMPTY_STRING, getBody)
             assertTrue(paginator.hasNext())
             assertEquals("first", paginator.next())
             assertTrue(paginator.hasNext())
@@ -79,7 +79,7 @@ class PaginatorTest {
         fun `test paginator as list`() {
             val firstResponse = Response(200, "first", mapOf("link" to listOf("<second>; rel=\"next\""), "pagination-total-results" to listOf("2")))
 
-            val paginator = Paginator(client, firstResponse, getBody)
+            val paginator = Paginator(client, firstResponse, EMPTY_STRING, getBody)
             val list = paginator.asSequence().toList()
             assertEquals(2, list.size)
             assertEquals("first", list[0])
@@ -93,7 +93,7 @@ class PaginatorTest {
         fun `test response paginator with one response`() {
             val firstResponse = Response(200, "first", emptyMap())
 
-            val paginator = ResponsePaginator(client, firstResponse, getBody)
+            val paginator = ResponsePaginator(client, firstResponse, EMPTY_STRING, getBody)
             assertTrue(paginator.hasNext())
             assertEquals("first", paginator.next().data)
             assertFalse(paginator.hasNext())
@@ -103,7 +103,7 @@ class PaginatorTest {
         fun `test response paginator with multiple responses`() {
             val firstResponse = Response(200, "first", mapOf("link" to listOf("<second>; rel=\"next\"")))
 
-            val paginator = ResponsePaginator(client, firstResponse, getBody)
+            val paginator = ResponsePaginator(client, firstResponse, EMPTY_STRING, getBody)
             assertTrue(paginator.hasNext())
             assertEquals("first", paginator.next().data)
             assertTrue(paginator.hasNext())
@@ -115,7 +115,7 @@ class PaginatorTest {
         fun `test response paginator with multiple responses and total results`() {
             val firstResponse = Response(200, "first", mapOf("link" to listOf("<second>; rel=\"next\""), "pagination-total-results" to listOf("2")))
 
-            val paginator = ResponsePaginator(client, firstResponse, getBody)
+            val paginator = ResponsePaginator(client, firstResponse, EMPTY_STRING, getBody)
             assertTrue(paginator.hasNext())
             assertEquals("first", paginator.next().data)
             assertTrue(paginator.hasNext())
@@ -124,25 +124,27 @@ class PaginatorTest {
             assertEquals(2, paginator.paginationTotalResults)
         }
 
-        @Test
-        fun `should return empty value when next response body is empty`() {
+        @ParameterizedTest
+        @ValueSource(strings = [EMPTY_STRING, "second", "some_value"])
+        fun `should return fallback value when next response body is empty`(fallbackBody: String) {
             val client = createRapidClient(createEmptyResponseEngine())
             val firstResponse = Response(200, "first", mapOf("link" to listOf("<second>; rel=\"next\""), "pagination-total-results" to listOf("2")))
 
-            val paginator = ResponsePaginator(client, firstResponse, getBody)
+            val paginator = ResponsePaginator(client, firstResponse, EMPTY_STRING, getBody)
             assertTrue(paginator.hasNext())
             assertEquals("first", paginator.next().data)
             assertTrue(paginator.hasNext())
             assertEquals(EMPTY_STRING, paginator.next().data)
             assertFalse(paginator.hasNext())
         }
 
-        @Test
-        fun `should return empty value when next response body is empty and gzip encoded`() {
+        @ParameterizedTest
+        @ValueSource(strings = [EMPTY_STRING, "second", "some_value"])
+        fun `should return fallback value when next response body is empty and gzip encoded`(fallbackBody: String) {
             val client = createRapidClient(createGzipEncodedEmptyResponseEngine())
             val firstResponse = Response(200, "first", mapOf("link" to listOf("<second>; rel=\"next\""), "pagination-total-results" to listOf("2")))
 
-            val paginator = ResponsePaginator(client, firstResponse, getBody)
+            val paginator = ResponsePaginator(client, firstResponse, EMPTY_STRING, getBody)
             assertTrue(paginator.hasNext())
             assertEquals("first", paginator.next().data)
             assertTrue(paginator.hasNext())

diff --git a/generator/openapi/src/main/kotlin/com/expediagroup/sdk/generators/openapi/MustacheHelpers.kt b/generator/openapi/src/main/kotlin/com/expediagroup/sdk/generators/openapi/MustacheHelpers.kt
@@ -31,7 +31,16 @@ val mustacheHelpers =
                 val paginationHeaders = listOf("Pagination-Total-Results", "Link")
                 val availableHeaders = operation.responses.find { it.code == "200" }?.headers?.filter { it.baseName in paginationHeaders }
                 if (availableHeaders?.size == paginationHeaders.size) {
-                    fragment.execute(writer)
+                    val fallbackBody =
+                        when {
+                            operation.returnType.startsWith("kotlin.collections.List") -> "emptyList()"
+                            operation.returnType.startsWith("kotlin.collections.Map") -> "emptyMap()"
+                            operation.returnType.startsWith("kotlin.collections.Set") -> "emptySet()"
+                            else -> ""
+                        }
+
+                    val context = mapOf("fallbackBody" to fallbackBody)
+                    fragment.execute(context, writer)
                 }
             }
         },