Provide ability to handle multiple custom fields with the same name.

src/WorkItemMigrator/JiraExport/IJiraProvider.cs

@@ -29,7 +29,11 @@ public interface IJiraProvider
 
         bool GetCustomFieldSerializer(string customType, out ICustomFieldValueSerializer serializer);
 
+        /// <inheritdoc cref="JiraProvider.GetCustomId"/>
         string GetCustomId(string propertyName);
+        /// <inheritdoc cref="JiraProvider.GetCustomIdList"/>
+        List<string> GetCustomIdList(string propertyName);
+
         Task<List<RevisionAction<JiraAttachment>>> DownloadAttachments(JiraRevision rev);
 
         IEnumerable<JObject> GetCommitRepositories(string issueId);

src/WorkItemMigrator/JiraExport/JiraMapper.cs

@@ -381,16 +381,19 @@ private HashSet<string> InitializeTypeMappings()
             return types;
         }
 
-        private Func<JiraRevision, (bool, object)> IfChanged<T>(string sourceField, bool isCustomField, Func<T, object> mapperFunc = null)
+        internal Func<JiraRevision, (bool, object)> IfChanged<T>(string sourceField, bool isCustomField, Func<T, object> mapperFunc = null)
         {
+            List<string> sourceFields = null;
             if (isCustomField)
             {
-                sourceField = _jiraProvider.GetCustomId(sourceField) ?? sourceField;
+                sourceFields = _jiraProvider.GetCustomIdList(sourceField);
             }
 
+            sourceFields = sourceFields ?? new List<string> { sourceField };
+
             return (r) =>
             {
-                if (r.Fields.TryGetValue(sourceField.ToLower(), out object value))
+                if (r.Fields.TryGetFirstValue(sourceFields, out object value))
                 {
                     if (mapperFunc != null)
                     {

src/WorkItemMigrator/JiraExport/JiraProvider.cs

@@ -412,9 +412,30 @@ public string GetUserEmail(string usernameOrAccountId)
             }
         }
 
+        /// <summary>
+        /// Return the custom field id corresponding to the given field/property name.
+        /// </summary>
+        /// <remarks>Blindly chooses the first matching value.  This is often right, but doesn't handle the scenario where a
+        /// Jira instance has multiple custom fields with the same name.  To handle that scenario, use <see cref="GetCustomIdList"/> instead.</remarks>
         public string GetCustomId(string propertyName)
         {
-            var customId = string.Empty;
+            var allIds = GetCustomIdList(propertyName);
+            var customId = allIds.FirstOrDefault();
+            if (allIds?.Count() > 1)
+            {
+                Logger.Log(LogLevel.Warning, $"Multiple fields found for {propertyName}. Selecting {customId}.");
+            }
+
+            return customId;
+        }
+
+        /// <summary>
+        /// Returns a list of custom field ids corresponding to the given field/property name. 
+        /// </summary>
+        /// <param name="propertyName">The property/field name of the custom field.</param>
+        /// <returns>One or more custom field ids that match the name provided.</returns>
+        public List<string> GetCustomIdList(string propertyName)
+        {
             JArray response = null;
 
             if (JiraNameFieldCache == null)
@@ -423,19 +444,24 @@ public string GetCustomId(string propertyName)
                 JiraNameFieldCache = CreateFieldCacheLookup(response, "name", "id");
             }
 
-            customId = GetItemFromFieldCache(propertyName, JiraNameFieldCache);
+            var customIds = GetItemListFromFieldCache(propertyName, JiraNameFieldCache);
 
-            if (string.IsNullOrEmpty(customId))
+            if (!customIds.Any())
             {
                 if (JiraKeyFieldCache == null)
                 {
                     response = response ?? (JArray)_jiraServiceWrapper.RestClient.ExecuteRequestAsync(Method.GET, $"{JiraApiV2}/field").Result;
                     JiraKeyFieldCache = CreateFieldCacheLookup(response, "key", "id");
                 }
-                customId = GetItemFromFieldCache(propertyName, JiraKeyFieldCache);
+                customIds = GetItemListFromFieldCache(propertyName, JiraKeyFieldCache);
+            }
+
+            if (customIds.Count == 0)
+            {
+                Logger.Log(LogLevel.Warning, $"Custom field {propertyName} could not be found.");
             }
 
-            return customId;
+            return customIds;
         }
 
         private ILookup<string, string> CreateFieldCacheLookup(JArray response, string key, string value)
@@ -446,19 +472,18 @@ private ILookup<string, string> CreateFieldCacheLookup(JArray response, string k
                 .ToLookup(l => l.key, l => l.value);
         }
 
-        private string GetItemFromFieldCache(string propertyName, ILookup<string, string> cache)
+        /// <summary>
+        /// Returns a list of cache values corresponding to the given name. 
+        /// </summary>
+        /// <param name="propertyName">The name to lookup in the cache.</param>
+        /// <param name="cache">The cache to be interrogated.</param>
+        /// <returns></returns>
+        private List<string> GetItemListFromFieldCache(string propertyName, ILookup<string, string> cache)
         {
-            string customId = null;
-            var query = cache.FirstOrDefault(x => x.Key.Equals(propertyName.ToLower()));
-            if (query != null)
-            {
-                customId = query.Any() ? query.First() : null;
-                if (query.Count() > 1)
-                {
-                    Logger.Log(LogLevel.Warning, $"Multiple fields found for {propertyName}. Selecting {customId}.");
-                }
-            }
-            return customId;
+            var fieldList = cache.FirstOrDefault(x => x.Key.Equals(propertyName.ToLower()))?.ToList() 
+                            ?? new List<string>(0);
+
+            return fieldList;
         }
 
         public IEnumerable<JObject> GetCommitRepositories(string issueId)

src/WorkItemMigrator/JiraExport/RevisionUtils/FieldMapperUtils.cs

@@ -12,8 +12,12 @@
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Text.RegularExpressions;
 
+[assembly: InternalsVisibleTo("Migration.Jira-Export.Tests")]
+
+
 namespace JiraExport
 {
     public static class FieldMapperUtils
@@ -183,6 +187,27 @@ public static object MapSprint(string iterationPathsString)
             return iterationPath;
         }
 
+        /// <summary>
+        /// Find the first custom field with the right name that has a value.
+        /// </summary>
+        /// <param name="fields"><see cref="JiraRevision.Fields">JiraRevision.Fields</see> dictionary.</param>
+        /// <param name="customFieldIds">The IDs of the Custom Fields to search - more than one custom field can have the same name.</param>
+        /// <param name="fieldValueObject">The value of the first field in the list that has a value.  Null if no values are found.</param>
+        /// <returns>True if one of the identified custom fields contains a value.</returns>
+        internal static bool TryGetFirstValue(this Dictionary<string,object> fields, List<string> customFieldIds, out object fieldValueObject)
+        {
+            foreach(var name in customFieldIds)
+            {
+                if (fields.TryGetValue(name, out fieldValueObject) && fieldValueObject != null)
+                {
+                    return true;
+                }
+            }
+
+            fieldValueObject = null;
+            return false;
+        }
+
         private static readonly Dictionary<string, decimal> CalculatedLexoRanks = new Dictionary<string, decimal>();
         private static readonly Dictionary<decimal, string> CalculatedRanks = new Dictionary<decimal, string>();
 

src/WorkItemMigrator/tests/Migration.Jira-Export.Tests/JiraMapperTests.cs

@@ -8,6 +8,7 @@
 using Newtonsoft.Json.Linq;
 using NSubstitute;
 using NUnit.Framework;
+using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
@@ -320,5 +321,107 @@ private JiraItem CreateJiraItem()
 
             return jiraItem;
         }
+
+
+        /*
+         * ******* IfChanged<T>()  ******
+         */
+
+        [Test]
+        public void IfChanged_SourceFieldExists_ReturnsTrueAndValue()
+        {
+            // Arrange
+            var jiraMapper = createJiraMapper();
+            //var revision = Substitute.For<JiraRevision>();
+            var item = _fixture.Create<JiraItem>();
+            var revision = new JiraRevision(parentItem: null);
+            revision.Fields = new Dictionary<string, object>();
+            revision.Fields.Add("sourceField", "value");
+
+            // Act
+            var (boolResult, valueResult) = jiraMapper.IfChanged<string>("sourceField", false) (revision);
+
+            // Assert
+            Assert.IsTrue(boolResult);
+            Assert.AreEqual("value", valueResult);
+        }
+
+        [Test]
+        public void IfChanged_SourceFieldDoesNotExist_ReturnsFalseAndNull()
+        {
+            // Arrange
+            var jiraMapper = createJiraMapper();
+            var item = _fixture.Create<JiraItem>();
+            var revision = new JiraRevision(parentItem: null);
+            revision.Fields = new Dictionary<string, object>();
+
+            // Act
+            var (boolResult, valueResult) = jiraMapper.IfChanged<string>("sourceField", false) (revision);
+
+            // Assert
+            Assert.IsFalse(boolResult);
+            Assert.IsNull(valueResult);
+        }
+
+        [Test]
+        public void IfChanged_CustomFieldExists_ReturnsTrueAndValue()
+        {
+            // Arrange
+            var jiraMapper = createJiraMapper();
+            var item = _fixture.Create<JiraItem>();
+            var revision = new JiraRevision(parentItem: null);
+            revision.Fields = new Dictionary<string, object>();
+            revision.Fields.Add("customField", "value");
+
+            var jiraProvider = Substitute.For<IJiraProvider>();
+            jiraProvider.GetCustomIdList("customField").Returns(new List<string> { "customField" });
+
+            // Act
+            var (boolResult, valueResult) = jiraMapper.IfChanged<string>("customField", true) (revision);
+
+            // Assert
+            Assert.IsTrue(boolResult);
+            Assert.AreEqual("value", valueResult);
+        }
+
+        [Test]
+        public void IfChanged_CustomFieldDoesNotExist_ReturnsFalseAndNull()
+        {
+            // Arrange
+            var jiraMapper = createJiraMapper();
+            var item = _fixture.Create<JiraItem>();
+            var revision = new JiraRevision(parentItem: null);
+            revision.Fields = new Dictionary<string, object>();
+
+            //_jiraProvider.GetCustomIdList("customField").Returns(new List<string> { "customField" });
+
+            // Act
+            var (boolResult, valueResult) = jiraMapper.IfChanged<string>("customField", true) (revision);
+
+            // Assert
+            Assert.IsFalse(boolResult);
+            Assert.IsNull(valueResult);
+        }
+
+        [Test]
+        public void IfChanged_SourceFieldExistsWithMapperFunc_ReturnsTrueAndMappedValue()
+        {
+            // Arrange
+            var jiraMapper = createJiraMapper();
+            var item = _fixture.Create<JiraItem>();
+            var revision = new JiraRevision(parentItem: null);
+            revision.Fields = new Dictionary<string, object>();
+            revision.Fields.Add("sourceField", 10);
+
+            // mapper takes expected 10 value and concatenates "XX" on the end.
+            Func<int, object> mapperFunc = (value) => value.ToString() + "XX";  
+
+            // Act
+            var (boolResult, valueResult) = jiraMapper.IfChanged<int>("sourceField", false, mapperFunc) (revision);
+
+            // Assert
+            Assert.IsTrue(boolResult);
+            Assert.AreEqual("10XX", valueResult);
+        }
     }
 }