transform pipelines accept items castable as xs:string as value fur r…

…elative URI

src/main/xslt/docbook.xsl

@@ -2,6 +2,7 @@
 <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                 xmlns:db="http://docbook.org/ns/docbook"
                 xmlns:dbe="http://docbook.org/ns/docbook/errors"
+                xmlns:err='http://www.w3.org/2005/xqt-errors'
                 xmlns:ext="http://docbook.org/extensions/xslt"
                 xmlns:f="http://docbook.org/ns/docbook/functions"
                 xmlns:fp="http://docbook.org/ns/docbook/functions/private"
@@ -101,43 +102,67 @@
     </xsl:map-entry>
   </xsl:map>
 </xsl:variable>
-
-<xsl:variable name="vp:transforms" as="map(*)*">
-  <xsl:for-each select="$transform-original">
-    <xsl:choose>
-      <xsl:when test=". instance of map(*)">
-        <xsl:sequence select="."/>
-      </xsl:when>
-      <xsl:when test=". instance of xs:string">
-        <xsl:sequence select="map {
-            'stylesheet-location': resolve-uri(., base-uri(/))
-          }"/>
-      </xsl:when>
-      <xsl:otherwise>
-        <xsl:sequence select="error($dbe:INVALID-TRANSFORM, 
-                                    'Each $transform-original must be a string or a map')"/>
-      </xsl:otherwise>
-    </xsl:choose>
+
+<xsl:template name="tp:stylesheet-locations" as="map(xs:string, xs:string)*">
+  <xsl:param name="locations" as="item()*"/>
+  <xsl:param name="purpose" as="xs:string"/>
+  <xsl:variable name="base-uri" as="xs:anyURI?">
+    <xsl:try>
+      <xsl:sequence select="base-uri(/)"/>
+      <xsl:catch/>
+    </xsl:try>
+  </xsl:variable>
+  <xsl:for-each select="$locations">
+      <xsl:choose>
+        <xsl:when test=". instance of map(xs:string, xs:string)">
+          <xsl:sequence select="."/>
+        </xsl:when>
+        <xsl:when test="not(exists($base-uri))">
+          <xsl:message
+            select="'WARNING: cannot resolve URI ' || xs:string(.) || ' in $' || $purpose || ': context item is absent.'"
+          />
+        </xsl:when>
+        <xsl:when test=". castable as xs:string">
+          <xsl:try>
+            <xsl:variable name="uri" as="xs:anyURI" select="resolve-uri(xs:string(.), $base-uri)"/>
+            <xsl:choose>
+              <xsl:when test="doc-available($uri)">
+                <xsl:sequence select="
+                    map {
+                      'stylesheet-location': xs:string($uri)
+                    }"/>
+              </xsl:when>
+              <xsl:otherwise>
+                <xsl:message
+                  select="'WARNING: cannot find resolved URI ' || $uri || ' in $' || $purpose"/>
+              </xsl:otherwise>
+            </xsl:choose>
+            <xsl:catch>
+              <xsl:message
+                select="'WARNING: cannot resolve URI ' || xs:string(.) || ' in $' || $purpose || ': ' || $err:description"
+              />
+            </xsl:catch>
+          </xsl:try>
+        </xsl:when>
+        <xsl:otherwise>
+          <xsl:sequence select="
+              error($dbe:INVALID-TRANSFORM,
+              'Each $' || $purpose || ' must be a string or a map')"/>
+        </xsl:otherwise>
+      </xsl:choose>
   </xsl:for-each>
+</xsl:template>  
 
+<xsl:variable name="vp:transforms" as="map(*)*">
+  <xsl:call-template name="tp:stylesheet-locations">
+    <xsl:with-param name="locations" select="$transform-original"/>
+    <xsl:with-param name="purpose" select="'transform-original'"/>
+  </xsl:call-template>
   <xsl:sequence select="$v:standard-transforms"/>
-
-  <xsl:for-each select="$transform-before">
-    <xsl:choose>
-      <xsl:when test=". instance of map(*)">
-        <xsl:sequence select="."/>
-      </xsl:when>
-      <xsl:when test=". instance of xs:string">
-        <xsl:sequence select="map {
-            'stylesheet-location': resolve-uri(., base-uri(/))
-          }"/>
-      </xsl:when>
-      <xsl:otherwise>
-        <xsl:sequence select="error($dbe:INVALID-TRANSFORM, 
-                                    'Each $transform-preprocessed must be a string or a map')"/>
-      </xsl:otherwise>
-    </xsl:choose>
-  </xsl:for-each>
+  <xsl:call-template name="tp:stylesheet-locations">
+    <xsl:with-param name="locations" select="$transform-before"/>
+    <xsl:with-param name="purpose" select="'transform-before'"/>
+  </xsl:call-template>
 </xsl:variable>
 
 <!-- If a document or element is being processed in the default
@@ -223,22 +248,10 @@
   </xsl:variable>
 
   <xsl:variable name="post-processing" as="map(*)*">
-    <xsl:for-each select="$transform-after">
-      <xsl:choose>
-        <xsl:when test=". instance of map(*)">
-          <xsl:sequence select="."/>
-        </xsl:when>
-        <xsl:when test=". instance of xs:string">
-          <xsl:sequence select="map {
-                                  'stylesheet-location': resolve-uri(., base-uri(/))
-                                }"/>
-        </xsl:when>
-        <xsl:otherwise>
-          <xsl:sequence select="error($dbe:INVALID-TRANSFORM, 
-                                      'Each $transform-preprocessed must be a string or a map')"/>
-        </xsl:otherwise>
-      </xsl:choose>
-    </xsl:for-each>
+    <xsl:call-template name="tp:stylesheet-locations">
+      <xsl:with-param name="locations" select="$transform-after"/>
+      <xsl:with-param name="purpose" select="'transform-after'"/>
+    </xsl:call-template>
   </xsl:variable>
 
   <xsl:variable name="result" as="document-node()">