Allow ech as an alias for ess

src/Elastic.Documentation/AppliesTo/ApplicableToJsonConverter.cs

@@ -131,7 +131,7 @@ public class ApplicableToJsonConverter : JsonConverter<ApplicableTo>
 				Self = deploymentProps.TryGetValue("self", out var self) ? new AppliesCollection(self.ToArray()) : null,
 				Ece = deploymentProps.TryGetValue("ece", out var ece) ? new AppliesCollection(ece.ToArray()) : null,
 				Eck = deploymentProps.TryGetValue("eck", out var eck) ? new AppliesCollection(eck.ToArray()) : null,
-				Ess = deploymentProps.TryGetValue("ess", out var ess) ? new AppliesCollection(ess.ToArray()) : null
+				Ess = deploymentProps.TryGetValue("ech", out var ess) || deploymentProps.TryGetValue("ess", out ess) ? new AppliesCollection(ess.ToArray()) : null
 			};
 		}
 

src/Elastic.Documentation/AppliesTo/ApplicableToYamlConverter.cs

@@ -15,7 +15,7 @@ public class ApplicableToYamlConverter(IReadOnlyCollection<string> productKeys)
 	private readonly string[] _knownKeys =
 	[
 		"stack", "deployment", "serverless", "product", // Applicability categories
-		"ece", "eck", "ess", "self", // Deployment options
+		"ece", "eck", "ess", "ech", "self", // Deployment options ("ech" aliasing to "ess")
 		"elasticsearch", "observability", "security", // Serverless flavors
 		.. productKeys
 	];
@@ -146,11 +146,17 @@ private static bool TryGetDeployment(Dictionary<object, object?> dictionary, Lis
 		var d = new DeploymentApplicability();
 		var assigned = false;
 
+		var hasEss = dictionary.ContainsKey("ess");
+		var hasEch = dictionary.ContainsKey("ech");
+		if (hasEss && hasEch)
+			diagnostics.Add((Severity.Warning, "Both 'ess' and 'ech' are defined. Move 'ess' content into 'ech' to avoid information loss."));
+
 		var mapping = new Dictionary<string, Action<AppliesCollection?>>
 		{
 			{ "ece", a => d.Ece = a },
 			{ "eck", a => d.Eck = a },
 			{ "ess", a => d.Ess = a },
+			{ "ech", a => d.Ess = a },
 			{ "self", a => d.Self = a }
 		};
 

tests/Elastic.Markdown.Tests/AppliesTo/ApplicableToJsonConverterRoundTripTests.cs

@@ -269,6 +269,43 @@ public void RoundTripComplexAllFieldsPopulated()
 		deserialized.ProductApplicability.ApmAgentDotnet.Should().BeEquivalentTo(original.ProductApplicability.ApmAgentDotnet);
 	}
 
+	[Fact]
+	public void RoundTripDeploymentEssRoundTripsCorrectly()
+	{
+		var original = new ApplicableTo
+		{
+			Deployment = new DeploymentApplicability
+			{
+				Ess = new AppliesCollection([new Applicability { Lifecycle = ProductLifecycle.GenerallyAvailable, Version = (VersionSpec)"9.0.0" }])
+			}
+		};
+
+		var json = JsonSerializer.Serialize(original, _options);
+		var deserialized = JsonSerializer.Deserialize<ApplicableTo>(json, _options);
+
+		deserialized.Should().NotBeNull();
+		deserialized!.Deployment.Should().NotBeNull();
+		deserialized.Deployment!.Ess.Should().BeEquivalentTo(original.Deployment!.Ess);
+	}
+
+	[Fact]
+	public void BothEssAndEchSubTypes_EchWins()
+	{
+		var json = """
+			[
+				{ "type": "deployment", "sub_type": "ess", "lifecycle": "ga", "version": "9.0.0" },
+				{ "type": "deployment", "sub_type": "ech", "lifecycle": "beta", "version": "9.1.0" }
+			]
+			""";
+
+		var deserialized = JsonSerializer.Deserialize<ApplicableTo>(json, _options);
+
+		deserialized.Should().NotBeNull();
+		deserialized!.Deployment.Should().NotBeNull();
+		deserialized.Deployment!.Ess.Should().NotBeNull();
+		deserialized.Deployment.Ess!.First().Lifecycle.Should().Be(ProductLifecycle.Beta);
+	}
+
 	[Fact]
 	public void RoundTripAllLifecycles()
 	{

tests/authoring/Applicability/AppliesToFrontMatter.fs

@@ -121,6 +121,74 @@ applies_to:
             )
         ))
 
+type ``parses ech as alias for ess`` () =
+    static let markdown = frontMatter """
+applies_to:
+   deployment:
+      ech: ga 9.0
+"""
+    [<Fact>]
+    let ``apply matches expected`` () =
+        markdown |> appliesTo (ApplicableTo(
+            Deployment=DeploymentApplicability(
+                Ess=AppliesCollection.op_Explicit "ga 9.0"
+            )
+        ))
+
+type ``parses ech with version alongside other deployment types`` () =
+    static let markdown = frontMatter """
+applies_to:
+   deployment:
+      ech: beta 9.1
+      eck: ga 9.0
+      ece: removed 9.2.0
+      self: unavailable 9.3.0
+"""
+    [<Fact>]
+    let ``apply matches expected`` () =
+        markdown |> appliesTo (ApplicableTo(
+            Deployment=DeploymentApplicability(
+                Ess=AppliesCollection.op_Explicit "beta 9.1",
+                Eck=AppliesCollection.op_Explicit "ga 9.0",
+                Ece=AppliesCollection.op_Explicit "removed 9.2.0",
+                Self=AppliesCollection.op_Explicit "unavailable 9.3.0"
+            )
+        ))
+
+type ``both ess and ech defined uses ech value and warns`` () =
+    static let markdown = frontMatter """
+applies_to:
+   deployment:
+      ess: ga 9.0
+      ech: beta 9.1
+"""
+    [<Fact>]
+    let ``ech value wins`` () =
+        markdown |> appliesTo (ApplicableTo(
+            Deployment=DeploymentApplicability(
+                Ess=AppliesCollection.op_Explicit "beta 9.1"
+            )
+        ))
+
+    [<Fact>]
+    let ``emits warning about both being defined`` () =
+        markdown |> hasWarning "Both 'ess' and 'ech' are defined"
+
+type ``parses ech at top level`` () =
+    static let markdown = frontMatter """
+applies_to:
+   ech: preview 9.1
+   stack: ga 9.1
+"""
+    [<Fact>]
+    let ``apply matches expected`` () =
+        markdown |> appliesTo (ApplicableTo(
+            Deployment=DeploymentApplicability(
+                Ess=AppliesCollection.op_Explicit "preview 9.1"
+            ),
+            Stack=AppliesCollection.op_Explicit "ga 9.1.0"
+        ))
+
 type ``parses product coming DEPRECATED`` () =
     static let markdown = frontMatter """
 applies_to:

tests/authoring/Inline/AppliesToRole.fs

@@ -53,6 +53,22 @@ This is an inline {applies_to}`ess: preview 9.1` element.
             )
         ))
 
+type ``parses nested ech moniker as ess`` () =
+    static let markdown = Setup.Markdown """
+
+This is an inline {applies_to}`ech: preview 9.1` element.
+"""
+
+    [<Fact>]
+    let ``parses to AppliesDirective`` () =
+        let directives = markdown |> converts "index.md" |> parses<AppliesToRole>
+        test <@ directives.Length = 1 @>
+        directives |> appliesToDirective (ApplicableTo(
+            Deployment=DeploymentApplicability(
+                Ess=AppliesCollection.op_Explicit "preview 9.1.0"
+            )
+        ))
+
 type ``parses {preview} shortcut`` () =
     static let markdown = Setup.Markdown """