Set default PDF variant values in options before generating PDF

We then have the PDF identifier and version set to the variant defaults during
generation.

tests/test_api.py

@@ -464,6 +464,12 @@ def test_pdfa_compressed(version, pdf_version):
     _run(f'--pdf-variant=pdf/a-{version}b - -', b'test')
 
 
+def test_pdfa1b_cidset():
+    stdout = _run('--pdf-variant=pdf/a-1b --uncompressed-pdf - -', b'test')
+    assert b'PDF-1.4' in stdout
+    assert b'CIDSet' in stdout
+
+
 def test_pdfua():
     stdout = _run('--pdf-variant=pdf/ua-1 --uncompressed-pdf - -', b'test')
     assert b'part="1"' in stdout

weasyprint/document.py

@@ -388,24 +388,24 @@ def write_pdf(self, target=None, zoom=1, finisher=None, **options):
         new_options = DEFAULT_OPTIONS.copy()
         new_options.update(options)
         options = new_options
-        pdf = generate_pdf(self, target, zoom, **options)
-
-        identifier = options['pdf_identifier']
-        compress = not options['uncompressed_pdf']
-        version = options['pdf_version']
-        variant = options['pdf_variant']
 
         # Set default PDF version for PDF variants.
-        if version is None and variant:
+        if variant := options['pdf_variant']:
             _, properties = VARIANTS[variant]
-            if 'version' in properties:
-                version = properties['version']
-            if 'identifier' in properties and not identifier:
-                identifier = properties['identifier']
+            if 'version' in properties and not options['pdf_version']:
+                options['pdf_version'] = properties['version']
+            if 'identifier' in properties and not options['pdf_identifier']:
+                options['pdf_identifier'] = properties['identifier']
+
+        pdf = generate_pdf(self, target, zoom, **options)
 
         if finisher:
             finisher(self, pdf)
 
+        identifier = options['pdf_identifier']
+        compress = not options['uncompressed_pdf']
+        version = options['pdf_version']
+
         if target is None:
             output = io.BytesIO()
             pdf.write(output, version, identifier, compress)