Create consistent data sync IDs for applicability switch (#2223)

* Create consistent data sync IDs for applicability switch

* Simplify

* Check against hardcoded id

Author: reakaleek

src/Elastic.Markdown/Myst/Directives/AppliesSwitch/AppliesSwitchBlock.cs

@@ -4,6 +4,7 @@
 
 using Elastic.Documentation.AppliesTo;
 using Elastic.Documentation.Configuration.Products;
+using Elastic.Documentation.Extensions;
 using Elastic.Markdown.Diagnostics;
 using Elastic.Markdown.Helpers;
 
@@ -67,23 +68,10 @@ public override void FinalizeAndValidate(ParserContext context)
 
 	public static string GenerateSyncKey(string appliesToDefinition, ProductsConfiguration productsConfiguration)
 	{
-		// Parse the YAML to get the ApplicableTo object, then use its hash
-		// This ensures both simple syntax and YAML objects produce consistent sync keys
-		try
-		{
-			var applicableTo = YamlSerialization.Deserialize<ApplicableTo>(appliesToDefinition, productsConfiguration);
-			if (applicableTo != null)
-			{
-				// Use the object's hash for a consistent, unique identifier
-				return $"applies-{System.Math.Abs(applicableTo.GetHashCode())}";
-			}
-		}
-		catch
-		{
-			// If parsing fails, fall back to the original definition
-		}
-
-		// Fallback to original definition if parsing fails
-		return appliesToDefinition.Slugify().Replace(".", "-");
+		var applicableTo = YamlSerialization.Deserialize<ApplicableTo>(appliesToDefinition, productsConfiguration);
+		// Use ShortId.Create for a stable, deterministic hash based on the normalized ToString()
+		// ToString() normalizes different YAML representations into a canonical form,
+		// ensuring semantically equivalent definitions get the same sync key
+		return $"applies-{ShortId.Create(applicableTo.ToString())}";
 	}
 }

tests/Elastic.Markdown.Tests/Directives/ApplicabilitySwitchTests.cs

@@ -170,10 +170,7 @@ public void ParsesSyncKey()
 
 		// Verify all sync keys have the expected hash-based format
 		foreach (var item in items)
-		{
 			item.SyncKey.Should().StartWith("applies-", "Sync key should start with 'applies-' prefix");
-			item.SyncKey.Should().MatchRegex(@"^applies-\d+$", "Sync key should be in format 'applies-{hash}'");
-		}
 
 		// Verify that different applies_to definitions produce different sync keys
 		items[0].SyncKey.Should().NotBe(items[1].SyncKey, "Different applies_to definitions should produce different sync keys");
@@ -220,7 +217,43 @@ public void GeneratesConsistentSyncKeysForYamlObjects()
 
 			// Also verify the key has the expected format
 			key1.Should().StartWith("applies-", "Sync key should start with 'applies-' prefix");
-			key1.Should().MatchRegex(@"^applies-\d+$", "Sync key should be in format 'applies-{hash}'");
+			key1.Should().MatchRegex(@"^applies-[0-9A-F]{8}$", "Sync key should be in format 'applies-{8 hex digits}'");
 		}
 	}
+
+	[Fact]
+	public void GeneratesDeterministicSyncKeysAcrossMultipleRuns()
+	{
+		var expectedKeys = new Dictionary<string, string>
+		{
+			// These are the actual SHA256-based hashes that should never change
+			{ "stack: ga 9.1", "applies-031B7112" },
+			{ "stack: preview 9.0", "applies-361F73DC" },
+			{ "ess: ga 8.11", "applies-32E204F7" },
+			{ "deployment: { ece: ga 9.0, ess: ga 9.1 }", "applies-D099CDEF" },
+			{ "serverless: all", "applies-A34B17C6" },
+		};
+
+		foreach (var (definition, expectedKey) in expectedKeys)
+		{
+			var actualKey = AppliesItemBlock.GenerateSyncKey(definition, Block!.Build.ProductsConfiguration);
+
+			actualKey.Should().Be(expectedKey,
+				$"The sync key for '{definition}' must match the expected value. " +
+				$"If this fails, the hash algorithm has changed and will break sync IDs across builds!");
+
+			// Also verify multiple invocations in this run produce the same key
+			var keys = Enumerable.Range(0, 5)
+				.Select(_ => AppliesItemBlock.GenerateSyncKey(definition, Block!.Build.ProductsConfiguration))
+				.ToList();
+
+			keys.Distinct().Should().HaveCount(1,
+				$"All invocations for '{definition}' should produce identical keys");
+		}
+
+		// Verify that different definitions produce different keys
+		var allKeys = expectedKeys.Values.ToList();
+		allKeys.Distinct().Should().HaveCount(expectedKeys.Count,
+			"Different applies_to definitions must produce different sync keys");
+	}
 }