Bug 335344 - External settings lost after changing language IDs, take 2

The original fix (a733900) only fixed part of the problem: It worked for
the case where a complete CExternalSetting was removed and replaced by a
different one, but not in the case where individual entries from a
CExternalSetting were moved to a different one, but others remained
(and, in both cases, the two CExternalSettings applied to the same
ICLanguageSetting).

This commit
- adds a test for the additional condition, which would previously fail
- reverts the previous fix, which is made redundant by the new one
- fixes both cases by applying removals before additions with
ICSettingEntry granularity per ICLanguageSetting rather than for whole
CExternalSettings.

Change-Id: I1b1ee7443b83189c29e458eef12be9cad6b3965d
Signed-off-by: Christian Walther <walther@indel.ch>

2 files changed, 20 insertions, 23 deletions

diff --git a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CExternalSettingsDeltaProcessor.java b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CExternalSettingsDeltaProcessor.java
index 62a77b63470..7420d51faa9 100644
--- a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CExternalSettingsDeltaProcessor.java
+++ b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CExternalSettingsDeltaProcessor.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2007, 2010 Intel Corporation and others.
+ * Copyright (c) 2007, 2018 Intel Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -10,6 +10,7 @@
  *
  * Contributors:
  * Intel Corporation - Initial API and implementation
+ * Christian Walther (Indel AG) - [335344] changing language IDs
  *******************************************************************************/
 package org.eclipse.cdt.internal.core.settings.model;
 
@@ -147,15 +148,7 @@ public class CExternalSettingsDeltaProcessor {
 		ICLanguageSetting setting = des.getLanguageSetting();
 		if (setting == null)
 			return false;
-
-		boolean changed = false;
-		for (ExtSettingsDelta delta : deltas) {
-			if (isSettingCompatible(setting, delta.fSetting)) {
-				if (applyDelta(setting, delta, kindMask))
-					changed = true;
-			}
-		}
-		return changed;
+		return applyDelta(setting, deltas, kindMask);
 	}
 
 	static boolean applyDelta(ICFolderDescription des, ExtSettingsDelta deltas[], int kindMask) {
@@ -173,16 +166,24 @@ public class CExternalSettingsDeltaProcessor {
 
 	static boolean applyDelta(ICLanguageSetting setting, ExtSettingsDelta[] deltas, int kindMask) {
 		boolean changed = false;
+		// apply removals before additions in case several deltas apply to the same setting
+		for (ExtSettingsDelta delta : deltas) {
+			if (isSettingCompatible(setting, delta.fSetting)) {
+				if (applyDelta(setting, delta, kindMask, false, true))
+					changed = true;
+			}
+		}
 		for (ExtSettingsDelta delta : deltas) {
 			if (isSettingCompatible(setting, delta.fSetting)) {
-				if (applyDelta(setting, delta, kindMask))
+				if (applyDelta(setting, delta, kindMask, true, false))
 					changed = true;
 			}
 		}
 		return changed;
 	}
 
-	static boolean applyDelta(ICLanguageSetting setting, ExtSettingsDelta delta, int kindMask) {
+	static boolean applyDelta(ICLanguageSetting setting, ExtSettingsDelta delta, int kindMask, boolean additions,
+			boolean removals) {
 		int kinds[] = KindBasedStore.getLanguageEntryKinds();
 		ICLanguageSettingEntry entries[];
 		ICSettingEntry diff[][];
@@ -196,7 +197,8 @@ public class CExternalSettingsDeltaProcessor {
 				continue;
 
 			entries = setting.getSettingEntries(kind);
-			List<ICLanguageSettingEntry> list = calculateUpdatedEntries(entries, diff[0], diff[1]);
+			List<ICLanguageSettingEntry> list = calculateUpdatedEntries(entries, additions ? diff[0] : null,
+					removals ? diff[1] : null);
 
 			if (list != null) {
 				setting.setSettingEntries(kind, list);
diff --git a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CExternalSettinsDeltaCalculator.java b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CExternalSettinsDeltaCalculator.java
index ef4681a7ec7..9f297793f45 100644
--- a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CExternalSettinsDeltaCalculator.java
+++ b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CExternalSettinsDeltaCalculator.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2007, 2011 Intel Corporation and others.
+ * Copyright (c) 2007, 2018 Intel Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -19,7 +19,6 @@ import java.util.Arrays;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -235,7 +234,7 @@ class CExternalSettinsDeltaCalculator {
 		if (oldSettings == null || oldSettings.length == 0)
 			return createDeltas(newSettings, true);
 
-		LinkedList<ExtSettingsDelta> deltaList = new LinkedList<>();
+		List<ExtSettingsDelta> deltaList = new ArrayList<>();
 
 		Map<ExtSettingMapKey, ICExternalSetting> newMap = toSettingsKeyMap(newSettings);
 		Map<ExtSettingMapKey, ICExternalSetting> oldMap = toSettingsKeyMap(oldSettings);
@@ -243,20 +242,16 @@ class CExternalSettinsDeltaCalculator {
 			CExternalSetting newSetting = (CExternalSetting) entry.getValue();
 			CExternalSetting oldSetting = (CExternalSetting) oldMap.remove(entry.getKey());
 			if (oldSetting == null) {
-				deltaList.addLast(new ExtSettingsDelta(newSetting, true));
+				deltaList.add(new ExtSettingsDelta(newSetting, true));
 			} else {
 				ExtSettingsDelta delta = createDelta(newSetting, oldSetting);
 				if (delta != null)
-					deltaList.addLast(delta);
+					deltaList.add(delta);
 			}
 		}
 
 		for (ICExternalSetting oldSettng : oldMap.values()) {
-			// removals must be prepended to the list so that they are applied before additions,
-			// otherwise a setting that was just added might be immediately removed again in
-			// CExternalSettingsDeltaProcessor.applyDelta(ICLanguageSetting, ExtSettingsDelta[], int)
-			// if the old and new setting only differ in their language sets and these overlap
-			deltaList.addFirst(new ExtSettingsDelta((CExternalSetting) oldSettng, false));
+			deltaList.add(new ExtSettingsDelta((CExternalSetting) oldSettng, false));
 		}
 
 		if (deltaList.size() == 0)