Bug 402177: Btree.insert returns wrong value

The javadoc for BTree.insert says "don't insert if the key was already
there, in which case we return the record that matched".

However, the implementation was returning the new record even when it
was not actually inserted.

This is a fix for the problem and a test case to demonstrate the issue.

Further Changes:
----------------
I have modified the code style as described in the comments in
https://git.eclipse.org/r/#/c/10804.

However, I'm still not sure what style is expected.  I've looked through
the CDT wiki a few times, especially the 'new developer' parts, but
haven't found anything relevant.  When I asked the question a few weeks
ago, the only reply was to use the "eclipse built-in style", which I
can't find in my preferences.  The default seems to be "K&R Style" (that
is what it is set to now, and I don't think that I would have changed
it), so that is what I've used here.

If I've missed the section in the wiki then a pointer would be greatly
appreciated.  Otherwise this topic would be a great topic for someone
that knows the answers to add to the wiki.

Change-Id: If079f235871fcdfbd35f1cba3f64cc3e33edaaec
Reviewed-on: https://git.eclipse.org/r/10804
Reviewed-by: Doug Schaefer <dschaefer@qnx.com>
IP-Clean: Doug Schaefer <dschaefer@qnx.com>
Tested-by: Doug Schaefer <dschaefer@qnx.com>

core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/internal/pdom/tests/BTreeTests.java

@@ -102,6 +102,24 @@ public class BTreeTests extends BaseTestCase {
 		}
 	}
 
+	/**
+	 * Bug 402177: BTree.insert should return the matching record if the new record was not inserted.
+	 */
+	public void testEquivalentRecordInsert_Bug402177() throws Exception {
+
+		init(8);
+		try {
+			BTMockRecord value1 = new BTMockRecord(db, 42);
+			BTMockRecord value2 = new BTMockRecord(db, 42);
+
+			long insert1 = btree.insert(value1.getRecord());
+			long insert2 = btree.insert(value2.getRecord());
+			assertEquals(insert1, insert2);
+		} finally {
+			finish();
+		}
+	}
+
 	/**
 	 * Insert/Delete a random number of records into/from the B-tree
 	 * @param seed the seed for obtaining the deterministic random testing

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/pdom/db/BTree.java

@@ -176,8 +176,8 @@ public class BTree {
 				} else if (compare < 0) {
 					lower= middle + 1;
 				} else {
-					// Found it, no insert, just return the record.
+					// Found it, no insert, just return the matched record.
-					return record;
+					return checkRec;
 				}
 			}
 		}