fix: preserve XML namespace declarations when capturing subtrees

src/adapter/etl-adapter-xml/src/Flow/ETL/Adapter/XML/XMLParserExtractor.php

@@ -5,6 +5,7 @@
 namespace Flow\ETL\Adapter\XML;
 
 use function Flow\ETL\DSL\array_to_rows;
+use function Flow\Types\DSL\type_string;
 use Flow\ETL\Exception\RuntimeException;
 use Flow\ETL\Extractor\{FileExtractor, Limitable, LimitableExtractor, PathFiltering, Signal};
 use Flow\ETL\{Extractor, FlowContext, Schema};
@@ -32,6 +33,11 @@ final class XMLParserExtractor implements Extractor, FileExtractor, LimitableExt
      */
     private array $elements = [];
 
+    /**
+     * @var list<array<string, string>>
+     */
+    private array $namespaceStack = [];
+
     private ?\XMLParser $parser = null;
 
     private ?Schema $schema = null;
@@ -79,6 +85,7 @@ public function endElementHandler(\XMLParser $parser, string $name) : void
         }
 
         array_pop($this->currentPath);
+        array_pop($this->namespaceStack);
     }
 
     public function extract(FlowContext $context) : \Generator
@@ -165,21 +172,39 @@ public function source() : Path
     public function startElementHandler(\XMLParser $parser, string $name, array $attrs) : void
     {
         $this->currentPath[] = $name;
-        $currentPathString = implode('/', $this->currentPath);
 
-        if ($currentPathString === $this->xmlNodePath || ($this->xmlNodePath === '' && \count($this->currentPath) === 1)) {
-            $this->capturing = true;
-            $this->writer()->startElement($name);
+        $namespaceDeclarations = [];
+        $otherAttributes = [];
 
-            foreach ($attrs as $key => $value) {
-                $this->writer()->writeAttribute($key, \is_scalar($value) ? (string) $value : '');
+        foreach ($attrs as $key => $value) {
+            if ($key === 'xmlns' || str_starts_with($key, 'xmlns:')) {
+                $namespaceDeclarations[$key] = \is_scalar($value) ? type_string()->cast($value) : '';
+            } else {
+                $otherAttributes[$key] = $value;
             }
+        }
+
+        $this->namespaceStack[] = $namespaceDeclarations;
+
+        $isCapturedRoot = implode('/', $this->currentPath) === $this->xmlNodePath || ($this->xmlNodePath === '' && \count($this->currentPath) === 1);
+
+        if ($isCapturedRoot) {
+            $this->capturing = true;
+            $namespacesToEmit = array_merge(...$this->namespaceStack);
         } elseif ($this->capturing) {
-            $this->writer()->startElement($name);
+            $namespacesToEmit = $namespaceDeclarations;
+        } else {
+            return;
+        }
 
-            foreach ($attrs as $key => $value) {
-                $this->writer()->writeAttribute($key, \is_scalar($value) ? (string) $value : '');
-            }
+        $this->writer()->startElement($name);
+
+        foreach ($namespacesToEmit as $nsKey => $nsValue) {
+            $this->writer()->writeAttribute($nsKey, $nsValue);
+        }
+
+        foreach ($otherAttributes as $key => $value) {
+            $this->writer()->writeAttribute($key, \is_scalar($value) ? type_string()->cast($value) : '');
         }
     }
 
@@ -221,6 +246,9 @@ private function freeParser() : void
             xml_parser_free($this->parser);
             $this->parser = null;
         }
+
+        $this->namespaceStack = [];
+        $this->currentPath = [];
     }
 
     private function parser() : \XMLParser

src/adapter/etl-adapter-xml/tests/Flow/ETL/Adapter/XML/Tests/Fixtures/namespaced_default.xml

@@ -0,0 +1,6 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<feed xmlns="http://example.com/default">
+    <entry>
+        <title>Product 1</title>
+    </entry>
+</feed>

src/adapter/etl-adapter-xml/tests/Flow/ETL/Adapter/XML/Tests/Fixtures/namespaced_feed.xml

@@ -0,0 +1,13 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<feed xmlns:g="http://base.google.com/ns/1.0" xmlns:c="http://example.com/custom">
+    <entry>
+        <g:id>1</g:id>
+        <g:title>Product 1</g:title>
+        <c:tag>alpha</c:tag>
+    </entry>
+    <entry>
+        <g:id>2</g:id>
+        <g:title>Product 2</g:title>
+        <c:tag>beta</c:tag>
+    </entry>
+</feed>

src/adapter/etl-adapter-xml/tests/Flow/ETL/Adapter/XML/Tests/Fixtures/namespaced_multi_ancestor.xml

@@ -0,0 +1,9 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<feed xmlns:a="http://example.com/a">
+    <group xmlns:b="http://example.com/b">
+        <entry>
+            <a:alpha>A</a:alpha>
+            <b:beta>B</b:beta>
+        </entry>
+    </group>
+</feed>

src/adapter/etl-adapter-xml/tests/Flow/ETL/Adapter/XML/Tests/Fixtures/namespaced_nested.xml

@@ -0,0 +1,9 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<feed xmlns:g="http://base.google.com/ns/1.0">
+    <group xmlns:g="http://example.com/override" xmlns:x="http://example.com/extra">
+        <entry>
+            <g:id>1</g:id>
+            <x:note>hello</x:note>
+        </entry>
+    </group>
+</feed>

src/adapter/etl-adapter-xml/tests/Flow/ETL/Adapter/XML/Tests/Fixtures/namespaced_on_captured_root.xml

@@ -0,0 +1,6 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<feed>
+    <entry xmlns:g="http://base.google.com/ns/1.0">
+        <g:title>Product 1</g:title>
+    </entry>
+</feed>

src/adapter/etl-adapter-xml/tests/Flow/ETL/Adapter/XML/Tests/Fixtures/namespaced_prefixed_attribute.xml

@@ -0,0 +1,6 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<feed xmlns:g="http://base.google.com/ns/1.0">
+    <entry xml:lang="en" g:priority="high">
+        <g:title>Product 1</g:title>
+    </entry>
+</feed>

src/adapter/etl-adapter-xml/tests/Flow/ETL/Adapter/XML/Tests/Fixtures/namespaced_sibling_isolation.xml

@@ -0,0 +1,9 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<feed>
+    <entry xmlns:g="http://example.com/first">
+        <g:note>first</g:note>
+    </entry>
+    <entry>
+        <plain>second</plain>
+    </entry>
+</feed>

src/adapter/etl-adapter-xml/tests/Flow/ETL/Adapter/XML/Tests/Integration/XMLParserExtractorTest.php

@@ -6,7 +6,7 @@
 
 use function Flow\ETL\Adapter\XML\from_xml;
 use function Flow\ETL\DSL\config;
-use function Flow\ETL\DSL\{df, flow_context, schema, xml_schema};
+use function Flow\ETL\DSL\{df, flow_context, ref, schema, xml_schema};
 use function Flow\Filesystem\DSL\path_real;
 use function Flow\Types\DSL\type_string;
 use Flow\ETL\Extractor\Signal;
@@ -111,6 +111,71 @@ public function test_reading_xml_from_path() : void
         );
     }
 
+    public function test_reading_xml_with_ancestor_namespace_declaration() : void
+    {
+        $rows = df()
+            ->read(from_xml(__DIR__ . '/../Fixtures/namespaced_feed.xml', 'feed/entry'))
+            ->withEntry('title', ref('node')->xpath('/entry/g:title')->domElementValue())
+            ->fetch();
+
+        self::assertSame(
+            ['Product 1', 'Product 2'],
+            [$rows[0]->valueOf('title'), $rows[1]->valueOf('title')],
+        );
+
+        $node = type_string()->cast($rows[0]->valueOf('node'));
+
+        self::assertStringContainsString('xmlns:g="http://base.google.com/ns/1.0"', $node);
+        self::assertStringContainsString('xmlns:c="http://example.com/custom"', $node);
+    }
+
+    public function test_reading_xml_with_default_namespace_declaration() : void
+    {
+        $node = type_string()->cast(df()
+            ->read(from_xml(__DIR__ . '/../Fixtures/namespaced_default.xml', 'feed/entry'))
+            ->fetch()[0]
+            ->valueOf('node'));
+
+        self::assertStringContainsString('xmlns="http://example.com/default"', $node);
+    }
+
+    public function test_reading_xml_with_multi_ancestor_namespace_merge() : void
+    {
+        $node = type_string()->cast(df()
+            ->read(from_xml(__DIR__ . '/../Fixtures/namespaced_multi_ancestor.xml', 'feed/group/entry'))
+            ->fetch()[0]
+            ->valueOf('node'));
+
+        self::assertStringContainsString('xmlns:a="http://example.com/a"', $node);
+        self::assertStringContainsString('xmlns:b="http://example.com/b"', $node);
+    }
+
+    public function test_reading_xml_with_namespace_on_captured_root() : void
+    {
+        $rows = df()
+            ->read(from_xml(__DIR__ . '/../Fixtures/namespaced_on_captured_root.xml', 'feed/entry'))
+            ->withEntry('title', ref('node')->xpath('/entry/g:title')->domElementValue())
+            ->fetch();
+
+        self::assertSame('Product 1', $rows[0]->valueOf('title'));
+        self::assertStringContainsString(
+            'xmlns:g="http://base.google.com/ns/1.0"',
+            type_string()->cast($rows[0]->valueOf('node')),
+        );
+    }
+
+    public function test_reading_xml_with_prefixed_attribute() : void
+    {
+        $node = type_string()->cast(df()
+            ->read(from_xml(__DIR__ . '/../Fixtures/namespaced_prefixed_attribute.xml', 'feed/entry'))
+            ->fetch()[0]
+            ->valueOf('node'));
+
+        self::assertStringContainsString('xmlns:g="http://base.google.com/ns/1.0"', $node);
+        self::assertStringContainsString('xml:lang="en"', $node);
+        self::assertStringContainsString('g:priority="high"', $node);
+    }
+
     public function test_reading_xml_with_schema() : void
     {
         $rows = df()
@@ -133,6 +198,50 @@ public function test_reading_xml_with_schema() : void
         }
     }
 
+    public function test_reading_xml_with_shadowed_namespace_declaration() : void
+    {
+        $node = type_string()->cast(df()
+            ->read(from_xml(__DIR__ . '/../Fixtures/namespaced_nested.xml', 'feed/group/entry'))
+            ->fetch()[0]
+            ->valueOf('node'));
+
+        self::assertStringContainsString('xmlns:g="http://example.com/override"', $node);
+        self::assertStringContainsString('xmlns:x="http://example.com/extra"', $node);
+        self::assertStringNotContainsString('http://base.google.com/ns/1.0', $node);
+    }
+
+    public function test_reading_xml_with_sibling_namespace_isolation() : void
+    {
+        $rows = df()
+            ->read(from_xml(__DIR__ . '/../Fixtures/namespaced_sibling_isolation.xml', 'feed/entry'))
+            ->fetch()
+            ->toArray();
+
+        $firstNode = type_string()->cast($rows[0]['node']);
+        $secondNode = type_string()->cast($rows[1]['node']);
+
+        self::assertStringContainsString('xmlns:g="http://example.com/first"', $firstNode);
+        self::assertStringNotContainsString('xmlns:g', $secondNode);
+        self::assertStringNotContainsString('http://example.com/first', $secondNode);
+    }
+
+    public function test_reading_xml_without_namespaces_is_unchanged() : void
+    {
+        self::assertXmlStringEqualsXmlString(
+            <<<'XML'
+<item item_attribute_01="1">
+  <id id_attribute_01="1">1</id>
+</item>
+XML,
+            type_string()->cast(
+                df()
+                    ->read(from_xml(__DIR__ . '/../Fixtures/simple_items_flat.xml', 'root/items/item'))
+                    ->fetch()[0]
+                    ->valueOf('node')
+            )
+        );
+    }
+
     public function test_signal_stop() : void
     {
         $extractor = (from_xml(path_real(__DIR__ . '/../Fixtures/flow_orders.xml')))->withXMLNodePath('root/row');