[xml] Error on including and importing schemas already parsed

[Oblivian <oblivian users sourceforge net>]

In looking for an answer some problems I've had importing and including schema in the same namespace I ran across these two messages and have not found any additional information.  I think the issue I ran into and the ones in the below links are caused by the same code.  Basically xmlschemas.c should allow imports/includes and redefinitions from the same schemaLocation.  I've attached a test case and the proposed patch to fix.

http://mail.gnome.org/archives/xml/2007-January/msg00042.html
http://mail.gnome.org/archives/xml/2007-January/msg00077.html

Since the svn code is the same as shown in msg00077 and I have found no further discourse on the subject, I'm assuming this was never addressed, but it would be useful for more complex schemas.

Attachment: test-cases.tar.bz2
Description: BZip2 compressed data

--- libxml2-svn-20090302.orig/xmlschemas.c	2009-03-02 19:29:01.000000000 -0500
+++ libxml2-svn-20090302/xmlschemas.c	2009-03-03 19:39:46.000000000 -0500
@@ -10343,27 +10343,39 @@
 
     /* Did we already fetch the doc? */
     if (bkt != NULL) {
-	/* TODO: The following nasty cases will produce an error. */
 	if ((WXS_IS_BUCKET_IMPMAIN(type)) && (! bkt->imported)) {
-	    /* We included/redefined and then try to import a schema. */
+	    /* 
+	    * We included/redefined and then try to import a schema,
+	    * but the new location provided for import was different.
+	    */
 	    if (schemaLocation == NULL)
 		schemaLocation = BAD_CAST "in_memory_buffer";
-	    xmlSchemaCustomErr(ACTXT_CAST pctxt, err,
-		invokingNode, NULL,
-		"The schema document '%s' cannot be imported, since "
-		"it was already included or redefined",
-		schemaLocation, NULL);
-	    goto exit;
+	    if (!xmlStrEqual(schemaLocation,
+		bkt->schemaLocation)) {
+		xmlSchemaCustomErr(ACTXT_CAST pctxt, err,
+		    invokingNode, NULL,
+		    "The schema document '%s' cannot be imported, since "
+		    "it was already included or redefined",
+		    schemaLocation, NULL);
+		goto exit;
+	    }
 	} else if ((! WXS_IS_BUCKET_IMPMAIN(type)) && (bkt->imported)) {
-	    /* We imported and then try to include/redefine a schema. */
+	    /*
+	    * We imported and then try to include/redefine a schema,
+	    * but the new location provided for the include/redefine
+	    * was different.
+	    */
 	    if (schemaLocation == NULL)
 		schemaLocation = BAD_CAST "in_memory_buffer";
-	    xmlSchemaCustomErr(ACTXT_CAST pctxt, err,
-		invokingNode, NULL,
-		"The schema document '%s' cannot be included or "
-		"redefined, since it was already imported",
-		schemaLocation, NULL);
-	    goto exit;
+	    if (!xmlStrEqual(schemaLocation,
+		bkt->schemaLocation)) {
+		xmlSchemaCustomErr(ACTXT_CAST pctxt, err,
+		    invokingNode, NULL,
+		    "The schema document '%s' cannot be included or "
+		    "redefined, since it was already imported",
+		    schemaLocation, NULL);
+		goto exit;
+	    }
 	}
     }