Improve alignment exception error reporting (#399)

Author: pmachapman

src/SIL.Machine/Corpora/CorpusAlignmentException.cs

@@ -4,14 +4,16 @@ namespace SIL.Machine.Corpora
 {
     public class CorpusAlignmentException : Exception
     {
-        public CorpusAlignmentException(string sourceRef, string targetRef)
+        public CorpusAlignmentException(string sourceRef, string targetRef, Exception innerException = null)
             : base(
-                $"Invalid format in {sourceRef} and {targetRef}. Mismatched key formats \"{sourceRef}\" and \"{targetRef}\". There may be an extraneous tab, missing ref, or inconsistent use of user-defined refs."
+                $"Invalid format in {sourceRef} and {targetRef}. Mismatched key formats \"{sourceRef}\" and \"{targetRef}\". There may be an extraneous tab, missing ref, or inconsistent use of user-defined refs.",
+                innerException
             ) { }
 
-        public CorpusAlignmentException(string[] refs)
+        public CorpusAlignmentException(string[] refs, Exception innerException = null)
             : base(
-                $"Invalid format in {string.Join(", ", refs)}. Mismatched key formats. There may be an extraneous tab, missing ref, or inconsistent use of user-defined refs."
+                $"Invalid format in {string.Join(", ", refs)}. Mismatched key formats. There may be an extraneous tab, missing ref, or inconsistent use of user-defined refs.",
+                innerException
             ) { }
     }
 }

src/SIL.Machine/Corpora/NParallelTextCorpus.cs

@@ -140,9 +140,12 @@ private IEnumerable<NParallelTextRow> GetRows(IList<IEnumerator<TextRow>> enumer
                         )
                         .ToList();
                 }
-                catch (ArgumentException)
+                catch (ArgumentException e)
                 {
-                    throw new CorpusAlignmentException(currentRows.Select(e => e.Ref.ToString()).ToArray());
+                    throw new CorpusAlignmentException(
+                        currentRows.Where(r => r != null).Select(r => r.Ref.ToString()).ToArray(),
+                        e
+                    );
                 }
                 List<int> nonMinRefIndexes = Enumerable.Range(0, N).Except(minRefIndexes).ToList();
                 if (minRefIndexes.Count < numberOfRemainingRows || minRefIndexes.Count(i => !completed[i]) == 1)
@@ -395,9 +398,9 @@ private bool CheckSameRefRows(IList<TextRow> sameRefRows, TextRow otherRow)
                 if (sameRefRows.Count > 0 && RowRefComparer.Compare(sameRefRows[0].Ref, otherRow.Ref) != 0)
                     sameRefRows.Clear();
             }
-            catch (ArgumentException)
+            catch (ArgumentException e)
             {
-                throw new CorpusAlignmentException(sameRefRows[0].Ref.ToString(), otherRow.Ref.ToString());
+                throw new CorpusAlignmentException(sameRefRows[0].Ref.ToString(), otherRow.Ref.ToString(), e);
             }
             return sameRefRows.Count > 0;
         }

src/SIL.Machine/Corpora/ParallelTextCorpus.cs

@@ -52,9 +52,9 @@ public override IEnumerable<ParallelTextRow> GetRows(IEnumerable<string> textIds
                                     ? RowRefComparer.Compare(nRow.Ref, alignmentEnumerator.Current.Ref)
                                     : 1;
                             }
-                            catch (ArgumentException)
+                            catch (ArgumentException e)
                             {
-                                throw new CorpusAlignmentException(nRow.NRefs.Select(r => r.ToString()).ToArray());
+                                throw new CorpusAlignmentException(nRow.NRefs.Select(r => r.ToString()).ToArray(), e);
                             }
                         } while (compareAlignmentCorpus < 0);
                     }