Partially implementing <xsl:import>.

DesignLiquido · Sep 21, 2024 · 7ad8343 · 7ad8343
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diff --git a/TODO.md b/TODO.md
@@ -6,5 +6,6 @@ XSLT-processor TODO
 * XSL:number
 * `attribute-set`, `decimal-format`, etc. (check `src/xslt.ts`)
 * `/html/body//ul/li|html/body//ol/li` has `/html/body//ul/li` evaluated by this XPath implementation as "absolute", and `/html/body//ol/li` as "relative". Both should be evaluated as "absolute".
+* Implement `<xsl:import>` with correct template precedence.
 
 Help is much appreciated. It seems to currently work for most of our purposes, but fixes and additions are always welcome!
diff --git a/src/xslt/xslt.ts b/src/xslt/xslt.ts
@@ -78,6 +78,7 @@ export class Xslt {
     outputMethod: 'xml' | 'html' | 'text' | 'name';
     outputOmitXmlDeclaration: string;
     version: string;
+    firstTemplateRan: boolean;
 
     constructor(
         options: Partial<XsltOptions> = {
@@ -110,6 +111,7 @@ export class Xslt {
             digit: '#',
             patternSeparator: ';'
         };
+        this.firstTemplateRan = false;
     }
 
     /**
@@ -210,7 +212,8 @@ export class Xslt {
                     await this.xsltIf(context, template, output);
                     break;
                 case 'import':
-                    throw new Error(`not implemented: ${template.localName}`);
+                    await this.xsltImport(context, template, output);
+                    break;
                 case 'include':
                     await this.xsltInclude(context, template, output);
                     break;
@@ -636,6 +639,40 @@ export class Xslt {
         }
     }
 
+    /**
+     * Implements `<xsl:import>`. For now the code is nearly identical to `<xsl:include>`, but there's
+     * no precedence evaluation implemented yet.
+     * @param context The Expression Context.
+     * @param template The template.
+     * @param output The output.
+     */
+    protected async xsltImport(context: ExprContext, template: XNode, output?: XNode) {
+        if (this.firstTemplateRan) {
+            throw new Error('<xsl:import> should be the first child node of <xsl:stylesheet> or <xsl:transform>.');
+        }
+
+        // We need to test here whether `window.fetch` is available or not.
+        // If it is a browser environemnt, it should be.
+        // Otherwise, we will need to import an equivalent library, like 'node-fetch'.
+        if (!global.globalThis.fetch) {
+            global.globalThis.fetch = fetch as any;
+            global.globalThis.Headers = Headers as any;
+            global.globalThis.Request = Request as any;
+            global.globalThis.Response = Response as any;
+        }
+
+        const hrefAttributeFind = template.childNodes.filter(n => n.nodeName === 'href');
+        if (hrefAttributeFind.length <= 0) {
+            throw new Error('<xsl:import> with no href attribute defined.');
+        }
+        const hrefAttribute = hrefAttributeFind[0];
+
+        const fetchTest = await global.globalThis.fetch(hrefAttribute.nodeValue);
+        const fetchResponse = await fetchTest.text();
+        const includedXslt = this.xmlParser.xmlParse(fetchResponse);
+        await this.xsltChildNodes(context, includedXslt.childNodes[0], output);
+    }
+
     /**
      * Implements `xsl:include`.
      * @param context The Expression Context.
@@ -765,6 +802,7 @@ export class Xslt {
         // in relative path, we force a 'self-and-siblings' axis.
         const nodes = this.xsltMatch(match, context, 'self-and-siblings');
         if (nodes.length > 0) {
+            this.firstTemplateRan = true;
             if (!context.inApplyTemplates) {
                 context.baseTemplateMatched = true;
             }

diff --git a/tests/xslt/import.test.tsx b/tests/xslt/import.test.tsx
@@ -0,0 +1,39 @@
+import assert from 'assert';
+
+import { XmlParser } from "../../src/dom";
+import { Xslt } from "../../src/xslt";
+
+describe('xsl:import', () => {
+    it('Trivial', async () => {
+        const xmlSource = `<html></html>`;
+
+        const xsltSource = `<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:fo="http://www.w3.org/1999/XSL/Format">
+            <xsl:output method="html" indent="yes"/>
+            <xsl:import href="https://raw.githubusercontent.com/DesignLiquido/xslt-processor/main/examples/head.xsl"/>
+        </xsl:stylesheet>`;
+
+        const xsltClass = new Xslt();
+        const xmlParser = new XmlParser();
+        const xml = xmlParser.xmlParse(xmlSource);
+        const xslt = xmlParser.xmlParse(xsltSource);
+        const resultingXml = await xsltClass.xsltProcess(xml, xslt);
+        assert.equal(resultingXml, '<html><head><link rel="stylesheet" type="text/css" href="style.css"><title/></head><body><div id="container"><div id="header"><div id="menu"><ul><li><a href="#" class="active">Home</a></li><li><a href="#">about</a></li></ul></div></div></div></body></html>');
+    });
+
+    it('Not the first child of `<xsl:stylesheet>` or `<xsl:transform>`', async () => {
+        const xmlSource = `<html></html>`;
+
+        const xsltSource = `<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:fo="http://www.w3.org/1999/XSL/Format">
+            <xsl:template match="/">
+                Anything
+            </xsl:template>
+            <xsl:import href="https://raw.githubusercontent.com/DesignLiquido/xslt-processor/main/examples/head.xsl"/>
+        </xsl:stylesheet>`;
+
+        const xsltClass = new Xslt();
+        const xmlParser = new XmlParser();
+        const xml = xmlParser.xmlParse(xmlSource);
+        const xslt = xmlParser.xmlParse(xsltSource);
+        assert.rejects(async () => await xsltClass.xsltProcess(xml, xslt));
+    });
+});