[GitHub] [daffodil] stevedlawrence commented on a change in pull request #748: Update alignment to improve correctness and prevent deadlocks

[GitBox <gi...@apache.org>]

stevedlawrence commented on a change in pull request #748:
URL: https://github.com/apache/daffodil/pull/748#discussion_r801985256



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File path: daffodil-core/src/main/scala/org/apache/daffodil/dsom/SchemaComponent.scala
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@@ -141,6 +141,17 @@ trait SchemaComponent
     res.distinct
   }
 
+  /**
+   * The lexically enclosing term, if one exists
+   */
+  final lazy val optEnclosingLexicalTerm: Option[Term] = {
+    optLexicalParent match {
+      case Some(t: Term) => Some(t)
+      case Some(sc: SchemaComponent) => sc.optEnclosingLexicalTerm
+      case _ => None

Review comment:
       Schemas are represented in memory by the DSOM, which has what I believe is a pretty up to date UML diagram:
   
   https://cwiki.apache.org/confluence/display/DAFFODIL/DFDL+Schema+Object+Model+%28DSOM%29+with+UML
   
   It's not super easy to follow, but if you follow the lines enough you can see the relationships. It's definitely helpful to see what is a Term and what isn't.
   
   For example, a local `<xs:complex>` is modeled by a `LocalComplexTypeDef`. This is not a `Term`, but has a lexical parent that could be, depending if the parent is a `LocalElementDecl` (a `Term) or a `GlobalElementDecl` (not a `Term`).
   
   Another example, a local `<xs:sequence>` is modeled by a `LocalSequence` (a Term), which may have a lexical parent that is a `LocalComplexTypeDef` (not a `Term`), which may have a lexical parent that is a `LocalElementDef` (a `Term`), etc.
   
   So this `optEnclsoingLexicalTerm` essentially skips over lexical parents like `LocalComplexTypeDef` since they really don't provide any information--you can't put any DFDL properties on them. `Term`s are usually the more interesting things, and what the alignment stuff cares about.
   




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