minor #20510 [Yaml] feature #59315 Add compact nested mapping support…

… to Dumper (gr8b)

This PR was squashed before being merged into the 7.3 branch.

Discussion
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[Yaml] feature #59315  Add compact nested mapping support to Dumper

Documentation update for YAML Dumper feature `Yaml::DUMP_COMPACT_NESTED_MAPPING`.

Commits
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12bb604 [Yaml] feature #59315  Add compact nested mapping support to Dumper

components/yaml.rst

@@ -450,6 +450,34 @@ By default, digit-only array keys are dumped as integers. You can use the
     $dumped = Yaml::dump([200 => 'foo'], 2, 4, Yaml::DUMP_NUMERIC_KEY_AS_STRING);
     // '200': foo
 
+Dumping Collection of Maps
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+By default, the collection of maps uses a hyphen on a separate line as a delimiter.
+To use the delimiter line as part of the map dump, use the ``Yaml::DUMP_COMPACT_NESTED_MAPPING`` flag.
+
+Dump without flag set:
+
+.. code-block:: yaml
+
+    planets:
+      -
+        name: Mercury
+        distance: 57910000
+      -
+        name: Jupiter
+        distance: 778500000
+
+Dump with ``Yaml::DUMP_COMPACT_NESTED_MAPPING`` flag set:
+
+.. code-block:: yaml
+
+    planets:
+      - name: Mercury
+        distance: 57910000
+      - name: Jupiter
+        distance: 778500000
+
 Syntax Validation
 ~~~~~~~~~~~~~~~~~