test: also test with preexisting

Author: ice1000

Diff for: cli-impl/src/main/java/org/aya/cli/utils/LiterateData.java

@@ -121,7 +121,10 @@ public record InjectedFrontMatter(
       var frontMatter = literate.findFrontMatter();
       var label = new Literate.Raw(Doc.plain(injected.datetimeKey + ": " + injected.datetimeValue));
       if (frontMatter != null) {
-        frontMatter.children().append(label);
+        // They must be non-empty because the front matter starts with a ---
+        var secondLast = frontMatter.children().size() - 2;
+        frontMatter.children().insert(secondLast, label);
+        frontMatter.children().insert(secondLast, Literate.EOL);
       } else {
         var delimiter = new Literate.Raw(Doc.plain("---"));
         frontMatter = new Literate.FrontMatter(MutableList.of(

Diff for: cli-impl/src/test/java/org/aya/test/literate/AyaMdParserTest.java

@@ -11,6 +11,7 @@
 import org.aya.cli.utils.LiterateData;
 import org.aya.generic.Constants;
 import org.aya.prettier.AyaPrettierOptions;
+import org.aya.pretty.doc.Doc;
 import org.aya.primitive.PrimFactory;
 import org.aya.producer.AyaParserImpl;
 import org.aya.resolve.context.EmptyContext;
@@ -144,12 +145,18 @@ public void testHighlight(String caseName) throws IOException {
   }
 
   @Test public void testTime() throws IOException {
-    var oneCase = new Case("heading");
+    var doc = lastUpdatedTest("heading");
+    assertTrue(doc.renderToMd().startsWith("---\nlastUpdated: "));
+    doc = lastUpdatedTest("frontmatter");
+    assertTrue(doc.renderToMd().startsWith("---\ntitle: Twitter\nlastUpdated: "));
+  }
+
+  private static @NotNull Doc lastUpdatedTest(String caseName) throws IOException {
+    var oneCase = new Case(caseName);
     var data = initLiterateTestCase(oneCase);
     var defaultFM = new LiterateData.InjectedFrontMatter("lastUpdated", StringUtil.timeInGitFormat());
-    var doc = data.literate().toDoc(data.stmts(), data.reporter().problems().toImmutableSeq(),
+    return data.literate().toDoc(data.stmts(), data.reporter().problems().toImmutableSeq(),
       defaultFM, AyaPrettierOptions.pretty()).toDoc();
-    assertTrue(doc.renderToMd().startsWith("---\nlastUpdated: "));
   }
 
   private @NotNull String trim(@NotNull String input) {

Diff for: cli-impl/src/test/resources/literate/frontmatter.aya.md

@@ -0,0 +1,4 @@
+---
+title: Twitter
+---
+# Hello, world!