Fix issue #65: Check source directories exist before writing to requirements

When using mxdev -n (no-fetch) or in offline mode, source directories may
not exist yet. Previously, mxdev would write references like '-e ./sources/package'
to requirements-mxdev.txt regardless, causing pip install to fail later.

This fix checks if source directories exist before writing them:
- If directory exists: Write normally (existing behavior)
- If directory doesn't exist: Write as comment with contextual warning

The warning message adapts based on context:
- In offline mode: Mentions offline mode and suggests removing -n and --offline flags
- Normal mode: Suggests removing -n flag to fetch sources

This fixes the mxmake two-stage installation workflow where mxdev -n runs
before sources are checked out.

Changes:
- Update write_dev_sources() to accept State parameter and check path existence
- Add contextual warning messages for missing directories
- Add tests for missing directories and offline mode warnings
- Update existing tests to pass State parameter

Fixes #65

Author: jensens

.claude/settings.local.json

@@ -9,7 +9,13 @@
       "Bash(git push:*)",
       "Bash(uvx:*)",
       "Bash(gh run view:*)",
-      "Bash(gh pr ready:*)"
+      "Bash(gh pr ready:*)",
+      "Bash(pip index:*)",
+      "Bash(python -m venv:*)",
+      "Bash(/tmp/test-mxdev-pypi/bin/pip install:*)",
+      "Read(//tmp/test-mxdev-50/sources/**)",
+      "Read(//tmp/test-mxdev-failing/sources/**)",
+      "Read(//tmp/test-mxdev-failing/**)"
     ],
     "deny": [],
     "ask": []

CHANGES.md

@@ -11,6 +11,8 @@
   [jensens]
 - Feature: #54: Add `fixed` install mode for non-editable installations to support production and Docker deployments. The new `editable` mode replaces `direct` as the default (same behavior, clearer naming). The `direct` mode is now deprecated but still works with a warning. Install modes: `editable` (with `-e`, for development), `fixed` (without `-e`, for production/Docker), `skip` (clone only).
   [jensens]
+- Fix #65: When generating requirements-mxdev.txt, check if source directories actually exist before writing package references. If a source directory doesn't exist (e.g., when using `mxdev -n` without prior fetch, or in offline mode), write it as a comment with a contextual warning instead of causing pip install to fail later. This fixes the mxmake two-stage installation workflow where `mxdev -n` runs before sources are checked out. Warning messages include context about offline mode when applicable.
+  [jensens]
 - Fix #35: Add `smart-threading` configuration option to prevent overlapping credential prompts when using HTTPS URLs. When enabled (default), HTTPS packages are processed serially first to ensure clean credential prompts, then other packages are processed in parallel for speed. Can be disabled with `smart-threading = false` if you have credential helpers configured.
   [jensens]
 - Fix #34: The `offline` configuration setting and `--offline` CLI flag are now properly respected to prevent VCS fetch/update operations. Previously, setting `offline = true` in mx.ini or using the `--offline` CLI flag was ignored, and VCS operations still occurred.

src/mxdev/processing.py

@@ -207,24 +207,53 @@ def fetch(state: State) -> None:
     )
 
 
-def write_dev_sources(fio, packages: dict[str, dict[str, typing.Any]]):
+def write_dev_sources(fio, packages: dict[str, dict[str, typing.Any]], state: State):
     """Create requirements configuration for fetched source packages."""
     if not packages:
         return
+
+    # Check if we're in offline mode or no-fetch mode
+    from .config import to_bool
+
+    offline_mode = to_bool(state.configuration.settings.get("offline", False))
+
     fio.write("#" * 79 + "\n")
     fio.write("# mxdev development sources\n")
+
     for name, package in packages.items():
         if package["install-mode"] == "skip":
             continue
+
+        # Check if source directory exists
+        source_path = Path(package["path"])
+
         extras = f"[{package['extras']}]" if package["extras"] else ""
         subdir = f"/{package['subdirectory']}" if package["subdirectory"] else ""
 
         # Add -e prefix only for 'editable' mode (not for 'fixed')
         prefix = "-e " if package["install-mode"] == "editable" else ""
-        install_line = f"""{prefix}./{package['target']}/{name}{subdir}{extras}\n"""
+        install_line = f"""{prefix}./{package['target']}/{name}{subdir}{extras}"""
+
+        if not source_path.exists():
+            # Source not checked out yet - write as comment with warning
+            if offline_mode:
+                reason = (
+                    f"Source directory does not exist: {source_path} (package: {name}). "
+                    f"This is expected in offline mode. Run mxdev without -n and --offline flags to fetch sources."
+                )
+            else:
+                reason = (
+                    f"Source directory does not exist: {source_path} (package: {name}). "
+                    f"This could be because -n (no-fetch) flag was used or sources haven't been checked out yet. "
+                    f"Run mxdev without -n flag to fetch sources."
+                )
+            logger.warning(reason)
+            fio.write(f"# {install_line}  # mxdev: source not checked out\n")
+        else:
+            # Source exists - write normally
+            logger.debug(f"-> {install_line}")
+            fio.write(f"{install_line}\n")
 
-        logger.debug(f"-> {install_line.strip()}")
-        fio.write(install_line)
     fio.write("\n\n")
 
 
@@ -289,6 +318,6 @@ def write(state: State) -> None:
             fio.write("#" * 79 + "\n")
             fio.write("# mxdev combined constraints\n")
             fio.write(f"-c {constraints_ref}\n\n")
-        write_dev_sources(fio, cfg.packages)
+        write_dev_sources(fio, cfg.packages, state)
         fio.writelines(requirements)
         write_main_package(fio, cfg.settings)