fix tests

Author: aaronburtle

src/Config/ObjectModel/RuntimeConfig.cs

@@ -380,10 +380,14 @@ public RuntimeConfig(
                             e.InnerException);
                     }
                 }
-                else
+                else if (fileSystem.File.Exists(dataSourceFile))
                 {
+                    // The file exists but failed to load (e.g. invalid JSON, deserialization error).
+                    // Throw to prevent silently skipping a broken child config.
+                    // Non-existent files are skipped gracefully to support late-configured scenarios
+                    // where data-source-files may reference files not present on the host.
                     throw new DataApiBuilderException(
-                        message: $"Failed to load datasource file: {dataSourceFile}. The file may not exist, contain invalid JSON, or have other configuration errors.",
+                        message: $"Failed to load datasource file: {dataSourceFile}. The file exists but contains invalid JSON or has other configuration errors.",
                         statusCode: HttpStatusCode.ServiceUnavailable,
                         subStatusCode: DataApiBuilderException.SubStatusCodes.ConfigValidationError);
                 }

src/Service.Tests/Configuration/RuntimeConfigLoaderTests.cs

@@ -227,42 +227,57 @@ public async Task ChildConfigWithMissingEnvVarsLoadsSuccessfully()
     }
 
     /// <summary>
-    /// Validates that when a child config file cannot be loaded (e.g. file not found, invalid JSON),
+    /// Validates that when a child config file exists but contains invalid content,
     /// the parent config loading fails instead of silently skipping the child.
+    /// Non-existent child files are intentionally skipped to support late-configured scenarios.
     /// Regression test for https://github.com/Azure/data-api-builder/issues/3271
     /// </summary>
     [TestMethod]
     public async Task ChildConfigLoadFailureHaltsParentConfigLoading()
     {
         string parentConfig = await File.ReadAllTextAsync("Multidab-config.MsSql.json");
 
-        JObject parentJson = JObject.Parse(parentConfig);
-        parentJson.Add("data-source-files", new JArray("nonexistent-child.json"));
-        string parentJsonStr = parentJson.ToString();
+        // Use a real temp file with invalid JSON so the file exists but fails to parse.
+        string invalidChildPath = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName() + ".json");
 
-        MockFileSystem fs = new(new Dictionary<string, MockFileData>()
+        try
         {
-            { "dab-config.json", new MockFileData(parentJsonStr) }
-            // nonexistent-child.json intentionally NOT added to the mock file system
-        });
+            await File.WriteAllTextAsync(invalidChildPath, "{ this is not valid json }");
 
-        FileSystemRuntimeConfigLoader loader = new(fs);
+            JObject parentJson = JObject.Parse(parentConfig);
+            parentJson.Add("data-source-files", new JArray(invalidChildPath));
+            string parentJsonStr = parentJson.ToString();
 
-        TextWriter originalError = Console.Error;
-        StringWriter sw = new();
-        Console.SetError(sw);
+            MockFileSystem fs = new(new Dictionary<string, MockFileData>()
+            {
+                { "dab-config.json", new MockFileData(parentJsonStr) }
+            });
 
-        try
-        {
-            bool loaded = loader.TryLoadConfig("dab-config.json", out RuntimeConfig _);
-            string error = sw.ToString();
+            FileSystemRuntimeConfigLoader loader = new(fs);
+
+            TextWriter originalError = Console.Error;
+            StringWriter sw = new();
+            Console.SetError(sw);
+
+            try
+            {
+                bool loaded = loader.TryLoadConfig("dab-config.json", out RuntimeConfig _);
+                string error = sw.ToString();
 
-            Assert.IsFalse(loaded, "Config loading should fail when a child config file cannot be loaded.");
-            Assert.IsTrue(error.Contains("Failed to load datasource file"), "Error message should indicate the child config file that failed to load.");
+                Assert.IsFalse(loaded, "Config loading should fail when a child config file exists but cannot be parsed.");
+                Assert.IsTrue(error.Contains("Failed to load datasource file"), "Error message should indicate the child config file that failed to load.");
+            }
+            finally
+            {
+                Console.SetError(originalError);
+            }
         }
         finally
         {
-            Console.SetError(originalError);
+            if (File.Exists(invalidChildPath))
+            {
+                File.Delete(invalidChildPath);
+            }
         }
     }
 }

src/Service.Tests/UnitTests/RuntimeConfigLoaderJsonDeserializerTests.cs

@@ -6,6 +6,7 @@
 using System.Data;
 using System.IO;
 using System.IO.Abstractions.TestingHelpers;
+using System.Linq;
 using System.Text;
 using System.Text.Json;
 using Azure.DataApiBuilder.Config;
@@ -485,10 +486,10 @@ public void TestLoadRuntimeConfigFailures(
         }
 
         /// <summary>
-        /// Method to validate that config loading fails when a sub-data source file is not found.
-        /// Previously this test asserted that the missing child was silently skipped;
-        /// after the fix for https://github.com/Azure/data-api-builder/issues/3271,
-        /// a missing child config now correctly causes the parent config to fail loading.
+        /// Method to validate that when a sub-data source file is not found, it is gracefully
+        /// skipped and the parent config loads successfully. Non-existent child files are
+        /// tolerated to support late-configured scenarios where data-source-files may reference
+        /// files not present on the host.
         /// </summary>
         [TestMethod]
         public void TestLoadRuntimeConfigSubFilesFails()
@@ -508,21 +509,8 @@ public void TestLoadRuntimeConfigSubFilesFails()
                                     ""data-source-files"":[""FileNotFound.json""],
                                     ""entities"":{ }
                                 }";
-
-            TextWriter originalError = Console.Error;
-            StringWriter sw = new();
-            Console.SetError(sw);
-
-            try
-            {
-                Assert.IsFalse(RuntimeConfigLoader.TryParseConfig(actualJson, out RuntimeConfig _), "Config loading should fail when a child config file cannot be found.");
-                string error = sw.ToString();
-                Assert.IsTrue(error.Contains("Failed to load datasource file"), "Error message should indicate the child config file that failed.");
-            }
-            finally
-            {
-                Console.SetError(originalError);
-            }
+            Assert.IsTrue(RuntimeConfigLoader.TryParseConfig(actualJson, out RuntimeConfig runtimeConfig), "Should parse the data-source-files correctly.");
+            Assert.IsTrue(runtimeConfig.ListAllDataSources().Count() == 1);
         }
 
         #endregion Negative Tests