From 4130b6cf4b77b0366a5742665cc6e7441a6584c2 Mon Sep 17 00:00:00 2001
From: Mike Gerwitz <gerwitzm@lovullo.com>
Date: Thu, 20 Nov 2014 23:39:23 -0500
Subject: [PATCH] apply-gen now ignores nullary functions

---
 src/transform/apply-gen.xsl    | 33 +++++++++++++++++++++++++++++++--
 test/transform/apply-gen.xspec | 17 +++++++++++++++++
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/src/transform/apply-gen.xsl b/src/transform/apply-gen.xsl
index 64af923..126a9e8 100644
--- a/src/transform/apply-gen.xsl
+++ b/src/transform/apply-gen.xsl
@@ -73,12 +73,41 @@
 </template>
 
 
+<!--
+  Skip nullary functions
+
+  Nullary functions (functions that accept no arguments) are either
+  thunks or are used purely for their side-effects.  We cannot
+  generate a definition for them of the same name, because our
+  definitions are nullary;  instead, we expect the caller to take
+  caution.
+
+  If a thunk, then the function will always return the same value and
+  it does not matter when processing occurs.
+
+  If used for side-effects, then order of processing may matter, but
+  this is a dangerous assumption in itself, since some implementations
+  may not evaluate the function until its return value is actually used.
+
+  Either way, handle it yourself.
+-->
+<template mode="fgen:create"
+          match="xsl:function[ not( xsl:param ) ]"
+          priority="5">
+  <comment>
+    <text>No definition generated for nullary function `</text>
+    <value-of select="@name" />
+    <text>'</text>
+  </comment>
+</template>
+
+
 <!--
   Process function definition
 -->
 <template mode="fgen:create"
-          match="xsl:function"
-          priority="5">
+          match="xsl:function[ xsl:param ]"
+          priority="4">
   <!-- we need to take care with namespacing; let's remove context
        dependencies and simply specify the full namespace URI -->
   <variable name="name-resolv"
diff --git a/test/transform/apply-gen.xspec b/test/transform/apply-gen.xspec
index e253a02..421e6ab 100644
--- a/test/transform/apply-gen.xspec
+++ b/test/transform/apply-gen.xspec
@@ -52,6 +52,23 @@
             context="xsl:stylesheet/xsl:function/*">
       <foo:bar />
     </expect>
+
+
+  <!-- if a function is nullary, then it is either a thunk or used for
+       its side-effects; we expect the user to take appropriate
+       caution -->
+  <scenario label="given a nullary function">
+    <context>
+      <xsl:stylesheet>
+        <xsl:function name="foo:bar">
+          <foo:thunk />
+        </xsl:function>
+      </xsl:stylesheet>
+    </context>
+
+    <!-- generating one would conflict, of couse -->
+    <expect label="does not generate a function"
+            test="not( xsl:stylesheet/xsl:function )" />
   </scenario>