Added early exit out of recursive settings expansion. Also added addi…

…tional documentation regarding deployment pipelines and settings (statiqdev/Statiq.Web#1020).

RELEASE.md

@@ -1,3 +1,7 @@
+# 1.0.0-beta.72
+
+- Added an improved warning message and early exit out of recursive settings expansion. 
+
 # 1.0.0-beta.71
 
 - Modified the behavior of computed metadata values to cache the value for a given document when using the `=>` prefix. The previous behavior that evaluates a computed value every time it's accessed can still be used by prefixing with `->` instead. In theory this change shouldn't result in any differences in behavior since documents are immutable in the first place (so caching wouldn't be any different from re-evaluating), but if you have computed metadata values that consider state outside the document (such as something like `DateTime.Now`), you'll need to switch those to use the `->` prefix instead.

src/core/Statiq.Common/Meta/TypeHelper.cs

@@ -104,17 +104,28 @@ public static object ExpandValue(string key, object value, IMetadata metadata)
             // Perform special expansions of IMetadataValue
             if (value is IMetadataValue metadataValue)
             {
-                // Warn if this looks like a recursive call
+                // Warn if this looks like a recursive call, and exit if we get here again
                 (string, IMetadataValue, int) expanding = (key, metadataValue, Thread.CurrentThread.ManagedThreadId);
-                if (!_expandingWarned.Contains(expanding) && !_expanding.Add(expanding))
+                if (!_expanding.Add(expanding))
                 {
-                    string displayString = (metadata as IDocument)?.ToSafeDisplayString();
-                    if (displayString is object)
+                    if (!_expandingWarned.Contains(expanding))
                     {
-                        displayString = " (" + displayString + ")";
+                        // First time so log a warning and continue trying to expand
+                        string displayString = (metadata as IDocument)?.ToSafeDisplayString();
+                        if (displayString is object)
+                        {
+                            displayString = " (" + displayString + ")";
+                        }
+
+                        IExecutionContext.Current.LogWarning(
+                            $"Potential recursive metadata expansion detected for key {key}{displayString}, is an actual value for the key properly defined somewhere?");
+                        _expandingWarned.Add(expanding);
+                    }
+                    else
+                    {
+                        // Second time, so return a default value
+                        return default;
                     }
-                    IExecutionContext.Current.LogWarning("Potential recursive metadata expansion detected for key " + key + displayString);
-                    _expandingWarned.Add(expanding);
                 }
 
                 // Expand the value
@@ -290,4 +301,4 @@ private static bool TryConvertEnumerable<T>(
             return true;
         }
     }
-}
+}