Add functionality to watch a directory and rebuild targets on file changes

.gitignore

@@ -76,3 +76,4 @@ __pycache__/
 
 *ipynb_checkpoints*
 hello_looper-master*
+venv/

markmeld/_version.py

@@ -1 +1,2 @@
-__version__ = "0.2.1-dev"
+__version__ = "0.3.0-dev"
+

markmeld/cli.py

@@ -8,6 +8,7 @@
 
 from .exceptions import *
 from .melder import MarkdownMelder
+from .watcher import MarkmeldWatchDog
 from .utilities import load_config_file, get_file_open_cmd
 from ._version import __version__
 
@@ -64,6 +65,14 @@ def build_argparser():
     # position 1
     parser.add_argument(dest="target", metavar="T", help="Target", nargs="?")
 
+    parser.add_argument(
+        "-w",
+        "--watch",
+        dest="watch",
+        help="Watch file for changes and autocompile",
+        action="store_true",
+    )
+
     parser.add_argument(
         "-l",
         "--list",
@@ -168,6 +177,22 @@ def main(test_args=None):
             _LOGGER.error(f"  {k}: {v}")
         sys.exit(0)
 
+    # meld it and watch
+    if args.watch:
+        watcher = MarkmeldWatchDog(
+            ".", cfg, args.target, print_only=args.print, vardump=args.dump
+        )
+        watcher.start()
+        try:
+            while watcher.is_alive():
+                watcher.join(1)
+        except KeyboardInterrupt:
+            _LOGGER.info("Stopping...")
+        finally:
+            watcher.stop()
+            watcher.join()
+            return
+
     _LOGGER.debug("Melding...")  # Meld it!
     mm = MarkdownMelder(cfg)
 

markmeld/watcher.py

@@ -0,0 +1,61 @@
+import logging
+from pathlib import Path
+from typing import Union
+from watchdog.observers import Observer
+from watchdog.events import LoggingEventHandler, DirModifiedEvent, FileModifiedEvent
+
+from .melder import Target
+from .melder import MarkdownMelder
+
+_LOGGER = logging.getLogger(__name__)
+
+
+class MarkmeldWatchDog(Observer):
+    """
+    Watchdog observer to watch for file changes.
+    """
+
+    def __init__(
+        self,
+        path: str,
+        cfg: dict,
+        target: str,
+        print_only: bool = False,
+        vardump: bool = False,
+    ):
+        super().__init__()
+        _LOGGER.info(f"Watching {path} for changes...")
+        self._mm = MarkdownMelder(cfg)
+        self.target = Target(cfg, target)
+        self.path = path
+        self.print_only = print_only
+        self.vardump = vardump
+
+        # init the ignore files list (just the output files)
+        if "output_file" in self.target.root_cfg["targets"][target]:
+            ignore_file_name = Path(
+                self.target.root_cfg["targets"][target]["output_file"]
+            ).name
+            self.ignore_files = [ignore_file_name]
+        else:
+            self.ignore_files = []
+
+        self.event_handler = LoggingEventHandler()
+        self.event_handler.on_modified = self.on_modified
+        self.schedule(self.event_handler, path, recursive=True)
+
+    def on_modified(self, event: Union[DirModifiedEvent, FileModifiedEvent]):
+        """
+        Check for file or directory modification and then rerun the melder.
+        """
+        p = Path(event.src_path)
+
+        # dont rebuild if the modified file or directory is the output file
+        # otherwise this causes an infinite loop
+        if p.name in self.ignore_files:
+            return
+
+        _LOGGER.info(f"File modified: {event.src_path}")
+        self._mm.build_target(
+            self.target.target_name, print_only=self.print_only, vardump=self.vardump
+        )

requirements/requirements-all.txt

@@ -4,3 +4,4 @@ logmuse
 pyyaml
 requests
 ubiquerg
+watchdog