scripts: add a XML preprocessor script

gdbus-codegen doesn't support conditions or pre-processing.

Rather than duplicating D-Bus interfaces for win32 adaptation, let's
have a preprocess step, so we can have platform-specific interfaces.

The python script is based on
https://github.com/peitaosu/XML-Preprocessor, with bug fixes, some
testing and replacing lxml dependency with the built-in xml module.

This preprocessing syntax style is not very common, but is similar to
the one provided by WiX (https://wixtoolset.org/docs/v3/overview/preprocessor/)
or wixl, that we adopted in QEMU for packaging the guest agent.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20230606115658.677673-5-marcandre.lureau@redhat.com>

MAINTAINERS

@@ -3202,6 +3202,7 @@ F: docs/interop/dbus*
 F: docs/sphinx/dbus*
 F: docs/sphinx/fakedbusdoc.py
 F: tests/qtest/dbus*
+F: scripts/xml-preprocess*
 
 Seccomp
 M: Daniel P. Berrange <berrange@redhat.com>

scripts/meson.build

@@ -1,3 +1,5 @@
 if stap.found()
   install_data('qemu-trace-stap', install_dir: get_option('bindir'))
 endif
+
+test('xml-preprocess', files('xml-preprocess-test.py'), suite: ['unit'])

scripts/xml-preprocess-test.py

@@ -0,0 +1,136 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2023 Red Hat, Inc.
+#
+# SPDX-License-Identifier: MIT
+"""Unit tests for xml-preprocess"""
+
+import contextlib
+import importlib
+import os
+import platform
+import subprocess
+import tempfile
+import unittest
+from io import StringIO
+
+xmlpp = importlib.import_module("xml-preprocess")
+
+
+class TestXmlPreprocess(unittest.TestCase):
+    """Tests for xml-preprocess.Preprocessor"""
+
+    def test_preprocess_xml(self):
+        with tempfile.NamedTemporaryFile(mode="w", delete=False) as temp_file:
+            temp_file.write("<root></root>")
+            temp_file_name = temp_file.name
+        result = xmlpp.preprocess_xml(temp_file_name)
+        self.assertEqual(result, "<root></root>")
+        os.remove(temp_file_name)
+
+    def test_save_xml(self):
+        with tempfile.NamedTemporaryFile(mode="w", delete=False) as temp_file:
+            temp_file_name = temp_file.name
+            xmlpp.save_xml("<root></root>", temp_file_name)
+        self.assertTrue(os.path.isfile(temp_file_name))
+        os.remove(temp_file_name)
+
+    def test_include(self):
+        with tempfile.NamedTemporaryFile(mode="w", delete=False) as inc_file:
+            inc_file.write("<included>Content from included file</included>")
+            inc_file_name = inc_file.name
+        xml_str = f"<?include {inc_file_name} ?>"
+        expected = "<included>Content from included file</included>"
+        xpp = xmlpp.Preprocessor()
+        result = xpp.preprocess(xml_str)
+        self.assertEqual(result, expected)
+        os.remove(inc_file_name)
+        self.assertRaises(FileNotFoundError, xpp.preprocess, xml_str)
+
+    def test_envvar(self):
+        os.environ["TEST_ENV_VAR"] = "TestValue"
+        xml_str = "<root>$(env.TEST_ENV_VAR)</root>"
+        expected = "<root>TestValue</root>"
+        xpp = xmlpp.Preprocessor()
+        result = xpp.preprocess(xml_str)
+        self.assertEqual(result, expected)
+        self.assertRaises(KeyError, xpp.preprocess, "$(env.UNKNOWN)")
+
+    def test_sys_var(self):
+        xml_str = "<root>$(sys.ARCH)</root>"
+        expected = f"<root>{platform.architecture()[0]}</root>"
+        xpp = xmlpp.Preprocessor()
+        result = xpp.preprocess(xml_str)
+        self.assertEqual(result, expected)
+        self.assertRaises(KeyError, xpp.preprocess, "$(sys.UNKNOWN)")
+
+    def test_cus_var(self):
+        xml_str = "<root>$(var.USER)</root>"
+        expected = "<root></root>"
+        xpp = xmlpp.Preprocessor()
+        result = xpp.preprocess(xml_str)
+        self.assertEqual(result, expected)
+        xml_str = "<?define USER=FOO?><root>$(var.USER)</root>"
+        expected = "<root>FOO</root>"
+        xpp = xmlpp.Preprocessor()
+        result = xpp.preprocess(xml_str)
+        self.assertEqual(result, expected)
+
+    def test_error_warning(self):
+        xml_str = "<root><?warning \"test warn\"?></root>"
+        expected = "<root></root>"
+        xpp = xmlpp.Preprocessor()
+        out = StringIO()
+        with contextlib.redirect_stdout(out):
+            result = xpp.preprocess(xml_str)
+        self.assertEqual(result, expected)
+        self.assertEqual(out.getvalue(), "[Warning]: test warn\n")
+        self.assertRaises(RuntimeError, xpp.preprocess, "<?error \"test\"?>")
+
+    def test_cmd(self):
+        xpp = xmlpp.Preprocessor()
+        result = xpp.preprocess('<root><?cmd "echo hello world"?></root>')
+        self.assertEqual(result, "<root>hello world</root>")
+        self.assertRaises(
+            subprocess.CalledProcessError,
+            xpp.preprocess, '<?cmd "test-unknown-cmd"?>'
+        )
+
+    def test_foreach(self):
+        xpp = xmlpp.Preprocessor()
+        result = xpp.preprocess(
+            '<root><?foreach x in a;b;c?>$(var.x)<?endforeach?></root>'
+        )
+        self.assertEqual(result, "<root>abc</root>")
+
+    def test_if_elseif(self):
+        xpp = xmlpp.Preprocessor()
+        result = xpp.preprocess('<root><?if True?>ok<?endif?></root>')
+        self.assertEqual(result, "<root>ok</root>")
+        result = xpp.preprocess('<root><?if False?>ok<?endif?></root>')
+        self.assertEqual(result, "<root></root>")
+        result = xpp.preprocess('<root><?if True?>ok<?else?>ko<?endif?></root>')
+        self.assertEqual(result, "<root>ok</root>")
+        result = xpp.preprocess('<root><?if False?>ok<?else?>ko<?endif?></root>')
+        self.assertEqual(result, "<root>ko</root>")
+        result = xpp.preprocess(
+            '<root><?if False?>ok<?elseif True?>ok2<?else?>ko<?endif?></root>'
+        )
+        self.assertEqual(result, "<root>ok2</root>")
+        result = xpp.preprocess(
+            '<root><?if False?>ok<?elseif False?>ok<?else?>ko<?endif?></root>'
+        )
+        self.assertEqual(result, "<root>ko</root>")
+
+    def test_ifdef(self):
+        xpp = xmlpp.Preprocessor()
+        result = xpp.preprocess('<root><?ifdef USER?>ok<?else?>ko<?endif?></root>')
+        self.assertEqual(result, "<root>ko</root>")
+        result = xpp.preprocess(
+            '<?define USER=FOO?><root><?ifdef USER?>ok<?else?>ko<?endif?></root>'
+        )
+        self.assertEqual(result, "<root>ok</root>")
+
+
+if __name__ == "__main__":
+    unittest.main()

scripts/xml-preprocess.py

@@ -0,0 +1,293 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2017-2019 Tony Su
+# Copyright (c) 2023 Red Hat, Inc.
+#
+# SPDX-License-Identifier: MIT
+#
+# Adapted from https://github.com/peitaosu/XML-Preprocessor
+#
+"""This is a XML Preprocessor which can be used to process your XML file before
+you use it, to process conditional statements, variables, iteration
+statements, error/warning, execute command, etc.
+
+## XML Schema
+
+### Include Files
+```
+<?include path/to/file ?>
+```
+
+### Variables
+```
+$(env.EnvironmentVariable)
+
+$(sys.SystemVariable)
+
+$(var.CustomVariable)
+```
+
+### Conditional Statements
+```
+<?if ?>
+
+<?ifdef ?>
+
+<?ifndef ?>
+
+<?else?>
+
+<?elseif ?>
+
+<?endif?>
+```
+
+### Iteration Statements
+```
+<?foreach VARNAME in 1;2;3?>
+    $(var.VARNAME)
+<?endforeach?>
+```
+
+### Errors and Warnings
+```
+<?error "This is error message!" ?>
+
+<?warning "This is warning message!" ?>
+```
+
+### Commands
+```
+<? cmd "echo hello world" ?>
+```
+"""
+
+import os
+import platform
+import re
+import subprocess
+import sys
+from typing import Optional
+from xml.dom import minidom
+
+
+class Preprocessor():
+    """This class holds the XML preprocessing state"""
+
+    def __init__(self):
+        self.sys_vars = {
+            "ARCH": platform.architecture()[0],
+            "SOURCE": os.path.abspath(__file__),
+            "CURRENT": os.getcwd(),
+        }
+        self.cus_vars = {}
+
+    def _pp_include(self, xml_str: str) -> str:
+        include_regex = r"(<\?include([\w\s\\/.:_-]+)\s*\?>)"
+        matches = re.findall(include_regex, xml_str)
+        for group_inc, group_xml in matches:
+            inc_file_path = group_xml.strip()
+            with open(inc_file_path, "r", encoding="utf-8") as inc_file:
+                inc_file_content = inc_file.read()
+                xml_str = xml_str.replace(group_inc, inc_file_content)
+        return xml_str
+
+    def _pp_env_var(self, xml_str: str) -> str:
+        envvar_regex = r"(\$\(env\.(\w+)\))"
+        matches = re.findall(envvar_regex, xml_str)
+        for group_env, group_var in matches:
+            xml_str = xml_str.replace(group_env, os.environ[group_var])
+        return xml_str
+
+    def _pp_sys_var(self, xml_str: str) -> str:
+        sysvar_regex = r"(\$\(sys\.(\w+)\))"
+        matches = re.findall(sysvar_regex, xml_str)
+        for group_sys, group_var in matches:
+            xml_str = xml_str.replace(group_sys, self.sys_vars[group_var])
+        return xml_str
+
+    def _pp_cus_var(self, xml_str: str) -> str:
+        define_regex = r"(<\?define\s*(\w+)\s*=\s*([\w\s\"]+)\s*\?>)"
+        matches = re.findall(define_regex, xml_str)
+        for group_def, group_name, group_var in matches:
+            group_name = group_name.strip()
+            group_var = group_var.strip().strip("\"")
+            self.cus_vars[group_name] = group_var
+            xml_str = xml_str.replace(group_def, "")
+        cusvar_regex = r"(\$\(var\.(\w+)\))"
+        matches = re.findall(cusvar_regex, xml_str)
+        for group_cus, group_var in matches:
+            xml_str = xml_str.replace(
+                group_cus,
+                self.cus_vars.get(group_var, "")
+            )
+        return xml_str
+
+    def _pp_foreach(self, xml_str: str) -> str:
+        foreach_regex = r"(<\?foreach\s+(\w+)\s+in\s+([\w;]+)\s*\?>(.*)<\?endforeach\?>)"
+        matches = re.findall(foreach_regex, xml_str)
+        for group_for, group_name, group_vars, group_text in matches:
+            group_texts = ""
+            for var in group_vars.split(";"):
+                self.cus_vars[group_name] = var
+                group_texts += self._pp_cus_var(group_text)
+            xml_str = xml_str.replace(group_for, group_texts)
+        return xml_str
+
+    def _pp_error_warning(self, xml_str: str) -> str:
+        error_regex = r"<\?error\s*\"([^\"]+)\"\s*\?>"
+        matches = re.findall(error_regex, xml_str)
+        for group_var in matches:
+            raise RuntimeError("[Error]: " + group_var)
+        warning_regex = r"(<\?warning\s*\"([^\"]+)\"\s*\?>)"
+        matches = re.findall(warning_regex, xml_str)
+        for group_wrn, group_var in matches:
+            print("[Warning]: " + group_var)
+            xml_str = xml_str.replace(group_wrn, "")
+        return xml_str
+
+    def _pp_if_eval(self, xml_str: str) -> str:
+        ifelif_regex = (
+            r"(<\?(if|elseif)\s*([^\"\s=<>!]+)\s*([!=<>]+)\s*\"*([^\"=<>!]+)\"*\s*\?>)"
+        )
+        matches = re.findall(ifelif_regex, xml_str)
+        for ifelif, tag, left, operator, right in matches:
+            if "<" in operator or ">" in operator:
+                result = eval(f"{left} {operator} {right}")
+            else:
+                result = eval(f'"{left}" {operator} "{right}"')
+            xml_str = xml_str.replace(ifelif, f"<?{tag} {result}?>")
+        return xml_str
+
+    def _pp_ifdef_ifndef(self, xml_str: str) -> str:
+        ifndef_regex = r"(<\?(ifdef|ifndef)\s*([\w]+)\s*\?>)"
+        matches = re.findall(ifndef_regex, xml_str)
+        for group_ifndef, group_tag, group_var in matches:
+            if group_tag == "ifdef":
+                result = group_var in self.cus_vars
+            else:
+                result = group_var not in self.cus_vars
+            xml_str = xml_str.replace(group_ifndef, f"<?if {result}?>")
+        return xml_str
+
+    def _pp_if_elseif(self, xml_str: str) -> str:
+        if_elif_else_regex = (
+            r"(<\?if\s(True|False)\?>"
+            r"(.*?)"
+            r"<\?elseif\s(True|False)\?>"
+            r"(.*?)"
+            r"<\?else\?>"
+            r"(.*?)"
+            r"<\?endif\?>)"
+        )
+        if_else_regex = (
+            r"(<\?if\s(True|False)\?>"
+            r"(.*?)"
+            r"<\?else\?>"
+            r"(.*?)"
+            r"<\?endif\?>)"
+        )
+        if_regex = r"(<\?if\s(True|False)\?>(.*?)<\?endif\?>)"
+        matches = re.findall(if_elif_else_regex, xml_str, re.DOTALL)
+        for (group_full, group_if, group_if_elif, group_elif,
+             group_elif_else, group_else) in matches:
+            result = ""
+            if group_if == "True":
+                result = group_if_elif
+            elif group_elif == "True":
+                result = group_elif_else
+            else:
+                result = group_else
+            xml_str = xml_str.replace(group_full, result)
+        matches = re.findall(if_else_regex, xml_str, re.DOTALL)
+        for group_full, group_if, group_if_else, group_else in matches:
+            result = ""
+            if group_if == "True":
+                result = group_if_else
+            else:
+                result = group_else
+            xml_str = xml_str.replace(group_full, result)
+        matches = re.findall(if_regex, xml_str, re.DOTALL)
+        for group_full, group_if, group_text in matches:
+            result = ""
+            if group_if == "True":
+                result = group_text
+            xml_str = xml_str.replace(group_full, result)
+        return xml_str
+
+    def _pp_command(self, xml_str: str) -> str:
+        cmd_regex = r"(<\?cmd\s*\"([^\"]+)\"\s*\?>)"
+        matches = re.findall(cmd_regex, xml_str)
+        for group_cmd, group_exec in matches:
+            output = subprocess.check_output(
+                group_exec, shell=True,
+                text=True, stderr=subprocess.STDOUT
+            )
+            xml_str = xml_str.replace(group_cmd, output)
+        return xml_str
+
+    def _pp_blanks(self, xml_str: str) -> str:
+        right_blank_regex = r">[\n\s\t\r]*"
+        left_blank_regex = r"[\n\s\t\r]*<"
+        xml_str = re.sub(right_blank_regex, ">", xml_str)
+        xml_str = re.sub(left_blank_regex, "<", xml_str)
+        return xml_str
+
+    def preprocess(self, xml_str: str) -> str:
+        fns = [
+            self._pp_blanks,
+            self._pp_include,
+            self._pp_foreach,
+            self._pp_env_var,
+            self._pp_sys_var,
+            self._pp_cus_var,
+            self._pp_if_eval,
+            self._pp_ifdef_ifndef,
+            self._pp_if_elseif,
+            self._pp_command,
+            self._pp_error_warning,
+        ]
+
+        while True:
+            changed = False
+            for func in fns:
+                out_xml = func(xml_str)
+                if not changed and out_xml != xml_str:
+                    changed = True
+                xml_str = out_xml
+            if not changed:
+                break
+
+        return xml_str
+
+
+def preprocess_xml(path: str) -> str:
+    with open(path, "r", encoding="utf-8") as original_file:
+        input_xml = original_file.read()
+
+        proc = Preprocessor()
+        return proc.preprocess(input_xml)
+
+
+def save_xml(xml_str: str, path: Optional[str]):
+    xml = minidom.parseString(xml_str)
+    with open(path, "w", encoding="utf-8") if path else sys.stdout as output_file:
+        output_file.write(xml.toprettyxml())
+
+
+def main():
+    if len(sys.argv) < 2:
+        print("Usage: xml-preprocessor input.xml [output.xml]")
+        sys.exit(1)
+
+    output_file = None
+    if len(sys.argv) == 3:
+        output_file = sys.argv[2]
+
+    input_file = sys.argv[1]
+    output_xml = preprocess_xml(input_file)
+    save_xml(output_xml, output_file)
+
+
+if __name__ == "__main__":
+    main()