Add the .Or method and Is Present, for other sources of config (and not deprecated aliases)

Author: anna-git

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/CompositeConfigurationSource.cs

@@ -58,6 +58,8 @@ public void Add(IConfigurationSource source)
         [PublicApi]
         IEnumerator IEnumerable.GetEnumerator() => _sources.GetEnumerator();
 
+        public bool IsPresent(string key) => _sources.Any(source => source.IsPresent(key));
+
         /// <inheritdoc />
         public ConfigurationResult<string> GetString(string key, IConfigurationTelemetry telemetry, Func<string, bool>? validator, bool recordValue)
         {

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/DictionaryConfigurationSource.cs

@@ -21,6 +21,8 @@ public DictionaryConfigurationSource(IReadOnlyDictionary<string, string> diction
 
     public override ConfigurationOrigins Origin => ConfigurationOrigins.Code;
 
+    public override bool IsPresent(string key) => _dictionary.ContainsKey(key);
+
     protected override string? GetString(string key)
     {
         _dictionary.TryGetValue(key, out var value);

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/DictionaryObjectConfigurationSource.cs

@@ -30,6 +30,8 @@ public DictionaryObjectConfigurationSource(IReadOnlyDictionary<string, object?>
 
     protected IReadOnlyDictionary<string, object?> Dictionary { get; }
 
+    public bool IsPresent(string key) => Dictionary.ContainsKey(key);
+
     protected virtual bool TryGetValue(string key, out object? value)
         => Dictionary.TryGetValue(key, out value);
 

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/EnvironmentConfigurationSource.cs

@@ -34,5 +34,7 @@ internal class EnvironmentConfigurationSource : StringConfigurationSource
 
             return null;
         }
+
+        public override bool IsPresent(string key) => GetString(key) is not null;
     }
 }

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/GlobalConfigurationSource.cs

@@ -97,7 +97,7 @@ internal static bool TryLoadJsonConfigurationFile(IConfigurationSource configura
 
             // if environment variable is not set, look for default file name in the current directory
             var configurationFileName = new ConfigurationBuilder(configurationSource, telemetry)
-                                       .WithKeys(ConfigurationKeys.ConfigurationFileName, "DD_DOTNET_TRACER_CONFIG_FILE")
+                                       .WithKeys(ConfigurationKeys.ConfigurationFileName)
                                        .AsString(
                                             getDefaultValue: () => Path.Combine(baseDirectory ?? GetCurrentDirectory(), "datadog.json"),
                                             validator: null);

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/HandsOffConfigurationSource.cs

@@ -24,4 +24,6 @@ internal sealed class HandsOffConfigurationSource(Dictionary<string, string> con
         _configurations.TryGetValue(key, out var value);
         return value;
     }
+
+    public override bool IsPresent(string key) => _configurations.ContainsKey(key);
 }

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/IConfigurationSource.cs

@@ -23,6 +23,11 @@ public interface IConfigurationSource
     /// </summary>
     public ConfigurationOrigins Origin { get; }
 
+    /// <summary>
+    /// Gets a value indicating whether the key is present in the configuration source.
+    /// </summary>
+    bool IsPresent(string key);
+
     /// <summary>
     /// Gets the <see cref="string"/> value of
     /// the setting with the specified key.

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/JsonConfigurationSource.cs

@@ -68,6 +68,8 @@ private protected JsonConfigurationSource(string json, ConfigurationOrigins orig
 
         internal bool TreatNullDictionaryAsEmpty { get; set; } = true;
 
+        public bool IsPresent(string key) => SelectToken(key) is not null;
+
         /// <summary>
         /// Creates a new <see cref="JsonConfigurationSource"/> instance
         /// by loading the JSON string from the specified file.

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/NameValueConfigurationSource.cs

@@ -46,5 +46,7 @@ internal NameValueConfigurationSource(NameValueCollection nameValueCollection, C
         {
             return _nameValueCollection[key];
         }
+
+        public override bool IsPresent(string key) => _nameValueCollection[key] is not null;
     }
 }

tracer/src/Datadog.Trace/Configuration/ConfigurationSources/NullConfigurationSource.cs

@@ -41,4 +41,6 @@ public ConfigurationResult<IDictionary<string, string>> GetDictionary(string key
 
     public ConfigurationResult<T> GetAs<T>(string key, IConfigurationTelemetry telemetry, Func<string, ParsingResult<T>> converter, Func<T, bool>? validator, bool recordValue)
         => ConfigurationResult<T>.NotFound();
+
+    public bool IsPresent(string key) => false;
 }