Fix Azure roles resources always redeploying (#12901)

* Fix Azure roles resources always redeploying

Everytime we check if we need to redeploy an Azure "roles" resource in run mode, we are getting a different CheckSum. This is because we are overwriting the "known parameters" like PrincipalId and PrincipalType with 'null' values, because these values aren't available yet.

The fix is to skip setting those known parameters, like we did in previous versions.

Fix #12651

Author: eerhardt

src/Aspire.Hosting.Azure/Provisioning/BicepUtilities.cs

@@ -14,17 +14,34 @@ namespace Aspire.Hosting.Azure.Provisioning;
 /// </summary>
 internal static class BicepUtilities
 {
+    // Known values since they will be filled in by the provisioner
+    private static readonly string[] s_knownParameterNames =
+    [
+        AzureBicepResource.KnownParameters.PrincipalName,
+        AzureBicepResource.KnownParameters.PrincipalId,
+        AzureBicepResource.KnownParameters.PrincipalType,
+        AzureBicepResource.KnownParameters.UserPrincipalId,
+        AzureBicepResource.KnownParameters.Location,
+    ];
+
     /// <summary>
     /// Converts the parameters to a JSON object compatible with the ARM template.
     /// </summary>
-    public static async Task SetParametersAsync(JsonObject parameters, AzureBicepResource resource, CancellationToken cancellationToken = default)
+    public static async Task SetParametersAsync(JsonObject parameters, AzureBicepResource resource, bool skipKnownValues = false, CancellationToken cancellationToken = default)
     {
         // Convert the parameters to a JSON object
         foreach (var parameter in resource.Parameters)
         {
             // Execute parameter values which are deferred.
             var parameterValue = parameter.Value is Func<object?> f ? f() : parameter.Value;
 
+            // Skip known parameters with 'null' values, like PrincipalType and PrincipalId, since they are filled in by the provisioner
+            // and are not available at this time. If we don't do this, the "roles" resources will be re-deployed every run.
+            if (skipKnownValues && s_knownParameterNames.Contains(parameter.Key) && parameterValue is null)
+            {
+                continue;
+            }
+
             parameters[parameter.Key] = new JsonObject()
             {
                 ["value"] = parameterValue switch
@@ -109,7 +126,7 @@ public static string GetChecksum(AzureBicepResource resource, JsonObject paramet
             _ = resource.GetBicepTemplateString();
 
             // Now overwrite with live object values skipping known values.
-            await SetParametersAsync(parameters, resource, cancellationToken: cancellationToken).ConfigureAwait(false);
+            await SetParametersAsync(parameters, resource, skipKnownValues: true, cancellationToken: cancellationToken).ConfigureAwait(false);
             if (scope is not null)
             {
                 await SetScopeAsync(scope, resource, cancellationToken).ConfigureAwait(false);
@@ -130,4 +147,4 @@ public static string GetChecksum(AzureBicepResource resource, JsonObject paramet
             (resource.TryGetLastAnnotation<ExistingAzureResourceAnnotation>(out var existingResource) ?
                 existingResource.ResourceGroup :
                 null);
-}
+}

tests/Aspire.Hosting.Azure.Tests/BicepUtilitiesTests.cs

@@ -428,11 +428,49 @@ public async Task GetCurrentChecksumAsync_ReturnsValidChecksumForValidParameters
         Assert.NotEmpty(result);
     }
 
+    /// <summary>
+    /// Ensures that known parameters are not overwritten when calculating the checksum.
+    /// This is important because if these known parameters are overwritten, it means the "roles"
+    /// resources will be redeployed every time the app is run.
+    /// </summary>
+    [Fact]
+    public async Task GetCurrentChecksumAsync_DoesNotOverwriteKnownParameters()
+    {
+        // Arrange
+        using var builder = TestDistributedApplicationBuilder.Create();
+        var bicep = builder.AddBicepTemplateString("test", "param name string").Resource;
+        bicep.Parameters[AzureBicepResource.KnownParameters.PrincipalType] = null;
+        bicep.Parameters[AzureBicepResource.KnownParameters.PrincipalId] = null;
+
+        var parameters = new JsonObject
+        {
+            [AzureBicepResource.KnownParameters.PrincipalType] = new JsonObject { ["value"] = "User" },
+            [AzureBicepResource.KnownParameters.PrincipalId] = new JsonObject { ["value"] = "1234" },
+        };
+
+        var configurationBuilder = new ConfigurationBuilder();
+        configurationBuilder.AddInMemoryCollection(new Dictionary<string, string?>
+        {
+            ["Parameters"] = parameters.ToJsonString()
+        });
+        var config = configurationBuilder.Build();
+
+        // Act
+        var result = await BicepUtilities.GetCurrentChecksumAsync(bicep, config);
+
+        // Assert
+        Assert.NotNull(result);
+
+        // verify the checksum is the same as using the config parameters directly
+        var expected = BicepUtilities.GetChecksum(bicep, parameters, scope: null);
+        Assert.Equal(expected, result);
+    }
+
     private sealed class ResourceWithConnectionString(string name, string connectionString) :
         Resource(name),
         IResourceWithConnectionString
     {
         public ReferenceExpression ConnectionStringExpression =>
            ReferenceExpression.Create($"{connectionString}");
     }
-}
+}