Document the os info contribution

Closes gh-45565

Author: philwebb

spring-boot-project/spring-boot-actuator-autoconfigure/src/docs/antora/modules/api/pages/rest/actuator/info.adoc

@@ -47,3 +47,12 @@ include::partial$rest/actuator/info/response-fields-beneath-git.adoc[]
 
 NOTE: This is the "simple" output.
 The contributor can also be configured to output all available data.
+
+
+[[info.retrieving.response-structure.os]]
+==== OS Response Structure
+
+The following table describes the structure of the `os` section of the response:
+
+[cols="2,1,3"]
+include::partial$rest/actuator/info/response-fields-beneath-os.adoc[]

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/info/InfoEndpointDocumentationTests.java

@@ -27,12 +27,15 @@
 import org.springframework.boot.actuate.info.GitInfoContributor;
 import org.springframework.boot.actuate.info.InfoContributor;
 import org.springframework.boot.actuate.info.InfoEndpoint;
+import org.springframework.boot.actuate.info.OsInfoContributor;
 import org.springframework.boot.info.BuildProperties;
 import org.springframework.boot.info.GitProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.restdocs.mockmvc.MockMvcRestDocumentation;
+import org.springframework.restdocs.payload.FieldDescriptor;
 import org.springframework.restdocs.payload.JsonFieldType;
+import org.springframework.restdocs.payload.ResponseFieldsSnippet;
 
 import static org.springframework.restdocs.payload.PayloadDocumentation.beneathPath;
 import static org.springframework.restdocs.payload.PayloadDocumentation.fieldWithPath;
@@ -51,23 +54,40 @@ class InfoEndpointDocumentationTests extends MockMvcEndpointDocumentationTests {
 	void info() throws Exception {
 		this.mockMvc.perform(get("/actuator/info"))
 			.andExpect(status().isOk())
-			.andDo(MockMvcRestDocumentation.document("info",
-					responseFields(beneathPath("git"),
-							fieldWithPath("branch").description("Name of the Git branch, if any."),
-							fieldWithPath("commit").description("Details of the Git commit, if any."),
-							fieldWithPath("commit.time").description("Timestamp of the commit, if any.")
-								.type(JsonFieldType.VARIES),
-							fieldWithPath("commit.id").description("ID of the commit, if any.")),
-					responseFields(beneathPath("build"),
-							fieldWithPath("artifact").description("Artifact ID of the application, if any.").optional(),
-							fieldWithPath("group").description("Group ID of the application, if any.").optional(),
-							fieldWithPath("name").description("Name of the application, if any.")
-								.type(JsonFieldType.STRING)
-								.optional(),
-							fieldWithPath("version").description("Version of the application, if any.").optional(),
-							fieldWithPath("time").description("Timestamp of when the application was built, if any.")
-								.type(JsonFieldType.VARIES)
-								.optional())));
+			.andDo(MockMvcRestDocumentation.document("info", gitInfo(), buildInfo(), osInfo()));
+	}
+
+	private ResponseFieldsSnippet gitInfo() {
+		return responseFields(beneathPath("git"),
+				fieldWithPath("branch").description("Name of the Git branch, if any."),
+				fieldWithPath("commit").description("Details of the Git commit, if any."),
+				fieldWithPath("commit.time").description("Timestamp of the commit, if any.").type(JsonFieldType.VARIES),
+				fieldWithPath("commit.id").description("ID of the commit, if any."));
+	}
+
+	private ResponseFieldsSnippet buildInfo() {
+		return responseFields(beneathPath("build"),
+				fieldWithPath("artifact").description("Artifact ID of the application, if any.").optional(),
+				fieldWithPath("group").description("Group ID of the application, if any.").optional(),
+				fieldWithPath("name").description("Name of the application, if any.")
+					.type(JsonFieldType.STRING)
+					.optional(),
+				fieldWithPath("version").description("Version of the application, if any.").optional(),
+				fieldWithPath("time").description("Timestamp of when the application was built, if any.")
+					.type(JsonFieldType.VARIES)
+					.optional());
+	}
+
+	private ResponseFieldsSnippet osInfo() {
+		return responseFields(beneathPath("os"), osInfoField("name", "Name"), osInfoField("version", "Version"),
+				osInfoField("arch", "Architecture"));
+	}
+
+	private FieldDescriptor osInfoField(String field, String desc) {
+		return fieldWithPath(field)
+			.description("Operating System " + desc + " (as obtained from the 'os." + field + "' system property).")
+			.type(JsonFieldType.STRING)
+			.optional();
 	}
 
 	@Configuration(proxyBeanMethods = false)
@@ -99,6 +119,11 @@ BuildInfoContributor buildInfoContributor() {
 			return new BuildInfoContributor(buildProperties);
 		}
 
+		@Bean
+		OsInfoContributor osInfoContributor() {
+			return new OsInfoContributor();
+		}
+
 	}
 
 }