Refactor: extract shared regeneration logic into regenerate-common.ts (#3340)

* Refactor: extract shared regeneration logic into regenerate-common.ts

Extract shared constants, interfaces, and utility functions from
regenerate.ts into a new regenerate-common.ts module to enable
code reuse across repos.

Extracted:
- SKIP_SPECS, SpecialFlags, BASE_AZURE_EMITTER_OPTIONS, BASE_EMITTER_OPTIONS
- TspCommand, RegenerateFlagsInput, RegenerateFlags, ProcessedEmitterOption,
  RegenerateConfig interfaces
- toPosix, getEmitterOption, getSubdirectories, defaultPackageName,
  buildOptions, runTaskPool, regenerate utility functions

regenerate.ts now imports from regenerate-common.ts and only contains
repo-specific configuration and overrides.

* Add changelog entry

* fix lint

* Organize requirements.txt with shared section markers and sorting

* Add test files and minor test fixes

- Add test_model_base_flatten_compatibility.py for flatten model tests
- Add test_typetest_union_discriminated.py for discriminated union tests
- Fix 'cadl-ranch' -> 'spector' in flatten test comments
- Add cspell ignore directives for property test files
- Fix import ordering and blank lines in test files

* Make generation-subdir test assertions conditional

generation-subdir is autorest-only, so guard its assertions with
existence checks to avoid failures in shared test runs.

* Add sync_from_typespec.py script for syncing shared files

Script syncs regenerate-common.ts, requirements.txt marker sections,
and test files from the typespec repo into autorest.python.

Author: msyyc

.chronus/changes/refactor-extract-regenerate-common-2026-2-13-0-0-0.md

@@ -0,0 +1,7 @@
+---
+changeKind: internal
+packages:
+  - "@azure-tools/typespec-python"
+---
+
+Extract shared regeneration logic into `regenerate-common.ts` for code reuse across repos

eng/scripts/sync_from_typespec.py

@@ -0,0 +1,258 @@
+#!/usr/bin/env python
+
+# --------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+# --------------------------------------------------------------------------------------------
+
+"""Sync shared files from the typespec repo (http-client-python) into this repo.
+
+The typespec repo is the source of truth for:
+  1. regenerate-common.ts — shared regeneration logic
+  2. requirements.txt — common test dependencies (delimited by marker comments)
+  3. Test files — mock API tests and test data
+
+Marker convention in requirements.txt:
+  # === common azure dependencies across repos ===
+  ...
+  # === end common azure dependencies across repos ===
+  # === common test dependencies across repos ===
+  ...
+  # === end common test dependencies across repos ===
+
+Usage:
+    python sync_from_typespec.py <local-typespec-repo-path>
+"""
+
+import argparse
+import os
+import re
+import shutil
+import subprocess
+import sys
+from pathlib import Path
+from typing import Dict, List, Set
+
+# --- Path configuration (relative to each repo root) ---
+
+TYPESPEC_COMMON_TS = Path("packages/http-client-python/eng/scripts/ci/regenerate-common.ts")
+AUTOREST_COMMON_TS = Path("packages/typespec-python/scripts/eng/regenerate-common.ts")
+
+TYPESPEC_TEST_DIR = Path("packages/http-client-python/generator/test")
+AUTOREST_TEST_DIR = Path("packages/typespec-python/test")
+
+# --- Marker patterns for requirements.txt sync ---
+
+_MARKER_PATTERN = re.compile(r"^# === (common .+ across repos) ===$")
+_END_MARKER_PATTERN = re.compile(r"^# === end (common .+ across repos) ===$")
+
+# --- Test file sync configuration ---
+
+_SKIP_DIRS: Set[str] = {"__pycache__", "generated", ".venv", "node_modules", ".tox"}
+
+_TEST_SUBDIRS = [
+    "generic_mock_api_tests",
+    os.path.join("azure", "mock_api_tests"),
+    os.path.join("unbranded", "mock_api_tests"),
+]
+
+# Files that remain repo-specific (different relative paths between repo layouts)
+_SKIP_FILES: Set[str] = {
+    os.path.join("generic_mock_api_tests", "conftest.py"),
+    os.path.join("azure", "mock_api_tests", "conftest.py"),
+    os.path.join("unbranded", "mock_api_tests", "conftest.py"),
+}
+
+_SKIP_EXTENSIONS: Set[str] = {".pyc"}
+_SKIP_FILENAMES: Set[str] = {"tox.ini", "requirements.txt", "dev_requirements.txt"}
+
+
+# ---------------------------------------------------------------------------
+# Requirements.txt marker-based sync
+# ---------------------------------------------------------------------------
+
+
+def _extract_marker_sections(filepath: Path) -> Dict[str, List[str]]:
+    """Extract content between marker comment pairs from a file.
+
+    Returns a dict mapping marker name to the lines between begin/end markers
+    (inclusive of both marker lines).
+    """
+    sections: Dict[str, List[str]] = {}
+    lines = filepath.read_text(encoding="utf-8").splitlines()
+
+    current_marker = None
+    current_lines: List[str] = []
+    for line in lines:
+        begin_match = _MARKER_PATTERN.match(line.strip())
+        end_match = _END_MARKER_PATTERN.match(line.strip())
+        if begin_match and current_marker is None:
+            current_marker = begin_match.group(1)
+            current_lines = [line]
+        elif end_match and current_marker is not None:
+            current_lines.append(line)
+            sections[current_marker] = current_lines
+            current_marker = None
+            current_lines = []
+        elif current_marker is not None:
+            current_lines.append(line)
+
+    return sections
+
+
+def _replace_marker_sections(filepath: Path, source_sections: Dict[str, List[str]]) -> None:
+    """Replace marker sections in a file with content from source_sections."""
+    lines = filepath.read_text(encoding="utf-8").splitlines()
+
+    result: List[str] = []
+    current_marker = None
+    for line in lines:
+        begin_match = _MARKER_PATTERN.match(line.strip())
+        end_match = _END_MARKER_PATTERN.match(line.strip())
+        if begin_match and current_marker is None:
+            current_marker = begin_match.group(1)
+            if current_marker in source_sections:
+                result.extend(source_sections[current_marker])
+            else:
+                result.append(line)
+        elif end_match and current_marker is not None:
+            if current_marker not in source_sections:
+                result.append(line)
+            current_marker = None
+        elif current_marker is None:
+            result.append(line)
+
+    filepath.write_text("\n".join(result) + "\n", encoding="utf-8", newline="\n")
+
+
+def sync_requirements(source: Path, target: Path) -> None:
+    """Sync common marker sections from source to target requirements.txt."""
+    source_sections = _extract_marker_sections(source)
+    if not source_sections:
+        print(f"  WARNING: no marker sections found in {source}, skipping")
+        return
+    _replace_marker_sections(target, source_sections)
+    print(f"  Synced requirements: {source.name} ({source.parent.name}/)")
+
+
+# ---------------------------------------------------------------------------
+# Test file sync
+# ---------------------------------------------------------------------------
+
+
+def _should_skip_file(rel_path: str, filename: str) -> bool:
+    """Return True if a file should not be synced."""
+    if filename in _SKIP_FILENAMES:
+        return True
+    if os.path.splitext(filename)[1] in _SKIP_EXTENSIONS:
+        return True
+    return rel_path in _SKIP_FILES
+
+
+def sync_test_files(source_root: Path, target_root: Path) -> None:
+    """Copy test files from typespec to autorest, skipping repo-specific files.
+
+    Only overwrites files that actually differ. Never deletes target-only files.
+    """
+    copied = 0
+    skipped = 0
+
+    for subdir in _TEST_SUBDIRS:
+        src_dir = source_root / subdir
+        if not src_dir.is_dir():
+            print(f"  WARNING: {src_dir} not found, skipping")
+            continue
+
+        for dirpath, dirnames, filenames in os.walk(src_dir):
+            dirnames[:] = [d for d in dirnames if d not in _SKIP_DIRS]
+
+            for filename in filenames:
+                src_file = Path(dirpath) / filename
+                rel_from_root = src_file.relative_to(source_root).as_posix()
+                rel_native = str(src_file.relative_to(source_root))
+
+                if _should_skip_file(rel_native, filename):
+                    skipped += 1
+                    continue
+
+                dst_file = target_root / rel_from_root
+                dst_file.parent.mkdir(parents=True, exist_ok=True)
+
+                if dst_file.is_file() and src_file.read_bytes() == dst_file.read_bytes():
+                    continue
+
+                shutil.copy2(src_file, dst_file)
+                copied += 1
+                print(f"  Copied: {rel_from_root}")
+
+    print(f"  Test files: {copied} copied, {skipped} skipped")
+
+
+# ---------------------------------------------------------------------------
+# Main
+# ---------------------------------------------------------------------------
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(
+        description="Sync shared files from the typespec repo (http-client-python) into autorest.python.",
+    )
+    parser.add_argument(
+        "typespec_repo",
+        type=Path,
+        help="Path to the local typespec repo root (e.g. C:/dev/typespec)",
+    )
+    args = parser.parse_args()
+
+    typespec_repo: Path = args.typespec_repo.resolve()
+    autorest_repo: Path = Path(__file__).resolve().parents[2]  # eng/scripts/.. -> repo root
+
+    if not typespec_repo.is_dir():
+        print(f"ERROR: typespec repo not found: {typespec_repo}", file=sys.stderr)
+        return 1
+
+    # 1. Sync regenerate-common.ts
+    src_ts = typespec_repo / TYPESPEC_COMMON_TS
+    dst_ts = autorest_repo / AUTOREST_COMMON_TS
+    if not src_ts.is_file():
+        print(f"ERROR: {src_ts} not found", file=sys.stderr)
+        return 1
+    shutil.copy2(src_ts, dst_ts)
+    print(f"Synced regenerate-common.ts")
+
+    # 2. Sync requirements.txt marker sections
+    for flavor in ("azure", "unbranded"):
+        src_req = typespec_repo / TYPESPEC_TEST_DIR / flavor / "requirements.txt"
+        dst_req = autorest_repo / AUTOREST_TEST_DIR / flavor / "requirements.txt"
+        if src_req.is_file() and dst_req.is_file():
+            sync_requirements(src_req, dst_req)
+        else:
+            print(f"  WARNING: requirements.txt not found for {flavor}, skipping")
+
+    # 3. Sync test files
+    print("Syncing test files...")
+    sync_test_files(
+        typespec_repo / TYPESPEC_TEST_DIR,
+        autorest_repo / AUTOREST_TEST_DIR,
+    )
+
+    # 4. Format TypeScript files
+    ts_python_dir = autorest_repo / "packages" / "typespec-python"
+    print("Running pnpm format...")
+    result = subprocess.run(
+        ["pnpm", "format"],
+        cwd=ts_python_dir,
+        capture_output=True,
+        text=True,
+        shell=(os.name == "nt"),
+    )
+    if result.returncode != 0:
+        print(f"WARNING: pnpm format failed:\n{result.stderr}", file=sys.stderr)
+    else:
+        print("pnpm format succeeded.")
+
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())