Add expand to the section block

slack-base/src/main/java/com/hubspot/slack/client/models/blocks/SectionIF.java

@@ -15,6 +15,10 @@
 import org.immutables.value.Value.Default;
 import org.immutables.value.Value.Immutable;
 
+/**
+ * Slack's section block displays text, optionally alongside fields and an accessory element.
+ * @see <a href="https://docs.slack.dev/reference/block-kit/blocks/section-block">Section block Docs</a>
+ */
 @Immutable
 @HubSpotStyle
 @JsonNaming(SnakeCaseStrategy.class)
@@ -38,6 +42,8 @@ default Text getText() {
 
   Optional<BlockElement> getAccessory();
 
+  Optional<Boolean> getExpand();
+
   @Check
   default void check() {
     boolean hasNonEmptyTextField =

slack-base/src/test/java/com/hubspot/slack/client/models/blocks/SectionBlockTest.java

@@ -0,0 +1,70 @@
+package com.hubspot.slack.client.models.blocks;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.hubspot.slack.client.jackson.ObjectMapperUtils;
+import com.hubspot.slack.client.models.blocks.objects.Text;
+import com.hubspot.slack.client.models.blocks.objects.TextType;
+import java.io.IOException;
+import org.junit.Test;
+
+public class SectionBlockTest {
+
+  private static final ObjectMapper MAPPER = ObjectMapperUtils.mapper();
+  private static final String SECTION_TEXT = "A long section that should never collapse";
+
+  @Test
+  public void itSerializesExpandWhenSet() {
+    Section section = Section
+      .builder()
+      .setText(Text.of(TextType.MARKDOWN, SECTION_TEXT))
+      .setExpand(true)
+      .build();
+
+    JsonNode json = MAPPER.valueToTree(section);
+
+    assertThat(json.get("expand").asBoolean()).isTrue();
+  }
+
+  @Test
+  public void itSerializesExpandFalseWhenSet() {
+    Section section = Section
+      .builder()
+      .setText(Text.of(TextType.MARKDOWN, SECTION_TEXT))
+      .setExpand(false)
+      .build();
+
+    JsonNode json = MAPPER.valueToTree(section);
+
+    assertThat(json.has("expand")).isTrue();
+    assertThat(json.get("expand").isBoolean()).isTrue();
+    assertThat(json.get("expand").booleanValue()).isFalse();
+  }
+
+  @Test
+  public void itOmitsExpandWhenNotSet() {
+    Section section = Section.of(Text.of(TextType.MARKDOWN, SECTION_TEXT));
+
+    JsonNode json = MAPPER.valueToTree(section);
+
+    assertThat(json.has("expand")).isFalse();
+  }
+
+  @Test
+  public void itDeserializesExpand() throws IOException {
+    String rawJson =
+      "{\"type\":\"section\",\"text\":{\"type\":\"mrkdwn\",\"text\":\"" +
+      SECTION_TEXT +
+      "\"},\"expand\":true}";
+
+    Block block = MAPPER.readValue(rawJson, Block.class);
+
+    assertThat(block)
+      .isInstanceOfSatisfying(
+        Section.class,
+        section -> assertThat(section.getExpand()).hasValue(true)
+      );
+  }
+}