Handle 422 response

Issue gh-32

api/github/src/main/java/com/github/api/GitHubApi.java

@@ -25,6 +25,7 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
+import java.util.logging.Logger;
 
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.core.JsonProcessingException;
@@ -37,6 +38,8 @@
  */
 public class GitHubApi {
 
+	private static final Logger LOGGER = Logger.getLogger(GitHubApi.class.getName());
+
 	private final HttpClient httpClient;
 
 	private final ObjectMapper objectMapper;
@@ -110,7 +113,18 @@ public void createMilestone(Repository repository, Milestone milestone) {
 			.POST(bodyValue(milestone))
 			.build();
 		// @formatter:on
-		performRequest(httpRequest, Void.class);
+		try {
+			performRequest(httpRequest, Void.class);
+		}
+		catch (HttpClientException ex) {
+			if (ex.getStatusCode() == 422) {
+				LOGGER.warning("Unable to create milestone %s: response=%s".formatted(milestone.title(),
+						ex.getResponseBody()));
+			}
+			else {
+				throw ex;
+			}
+		}
 	}
 
 	/**

api/github/src/test/java/com/github/api/GitHubApiTests.java

@@ -132,6 +132,26 @@ public void createMilestoneWhenValidParametersThenSuccess() throws Exception {
 		json.assertThat("$.due_on", is("2022-05-04T12:00:00Z"));
 	}
 
+	@Test
+	public void createMilestoneWhenAlreadyExistsThenSuccessWithWarning() throws Exception {
+		this.server.enqueue(json("CreateMilestoneErrorResponse.json").setResponseCode(422));
+
+		var dueOn = Instant.parse("2022-05-04T12:00:00Z");
+		var milestone = new Milestone("1.0.0", null, dueOn);
+		this.githubApi.createMilestone(this.repository, milestone);
+
+		var recordedRequest = this.server.takeRequest();
+		assertThat(recordedRequest.getMethod()).isEqualTo("POST");
+		assertThat(recordedRequest.getPath()).isEqualTo("/repos/spring-projects/spring-security/milestones");
+		assertThat(recordedRequest.getHeader("Accept")).isEqualTo("application/json");
+		assertThat(recordedRequest.getHeader("Content-Type")).isEqualTo("application/json");
+		assertThat(recordedRequest.getHeader("Authorization")).isEqualTo("Bearer %s".formatted(AUTH_TOKEN));
+
+		var json = JsonAssert.with(recordedRequest.getBody().readString(Charset.defaultCharset()));
+		json.assertThat("$.title", is("1.0.0"));
+		json.assertThat("$.due_on", is("2022-05-04T12:00:00Z"));
+	}
+
 	@Test
 	public void getMilestonesWhenExistsThenSuccess() throws Exception {
 		this.server.enqueue(json("MilestonesResponse.json"));

api/github/src/test/resources/CreateMilestoneErrorResponse.json

@@ -0,0 +1 @@
+{"message":"Validation Failed","errors":[{"resource":"Milestone","code":"already_exists","field":"title"}],"documentation_url":"https://docs.github.com/rest/issues/milestones#create-a-milestone"}

api/sagan/src/test/java/io/spring/api/SaganApiTests.java

@@ -159,7 +159,8 @@ public void createReleaseWhenValidParametersThenSuccess() throws Exception {
 
 		var json = JsonAssert.with(recordedRequest.getBody().readString(Charset.defaultCharset()));
 		json.assertThat("$.version", is("6.1.0"));
-		json.assertThat("$.referenceDocUrl", is("https://docs.spring.io/spring-security/reference/{version}/index.html"));
+		json.assertThat("$.referenceDocUrl",
+				is("https://docs.spring.io/spring-security/reference/{version}/index.html"));
 		json.assertThat("$.apiDocUrl", is("https://docs.spring.io/spring-security/site/docs/{version}/api/"));
 		json.assertThat("$.status", is("GENERAL_AVAILABILITY"));
 		json.assertThat("$.current", is(true));