add yaml.tool similar to json.tool

lib/yaml/tool.py

@@ -0,0 +1,109 @@
+r"""Command-line tool to validate and pretty-print YAML
+
+Usage::
+
+    $ echo '{"json":"obj"}' | python -m yaml.tool
+    ---
+    json: obj
+    $ echo '{ 1.2:3.4' | python -m yaml.tool
+    while parsing a flow mapping
+      in "<stdin>", line 1, column 1
+    expected ',' or '}', but got '<stream end>'
+      in "<stdin>", line 2, column 1
+
+
+"""
+
+import argparse
+
+import yaml
+
+try:
+    from yaml import CSafeDumper as SafeDumper
+    from yaml import CSafeLoader as SafeLoader
+except ImportError:
+    from yaml import SafeDumper, SafeLoader
+import sys
+from pathlib import Path
+
+
+def main():
+    prog = "python -m yaml.tool"
+    description = (
+        "A simple command line interface for PyYAML module "
+        "to validate and pretty-print YAML objects."
+    )
+    parser = argparse.ArgumentParser(prog=prog, description=description)
+    parser.add_argument(
+        "infile",
+        nargs="?",
+        type=argparse.FileType(encoding="utf-8"),
+        help="a YAML file to be validated or pretty-printed",
+        default=sys.stdin,
+    )
+    parser.add_argument(
+        "outfile",
+        nargs="?",
+        type=Path,
+        help="write the output of infile to outfile",
+        default=None,
+    )
+    parser.add_argument(
+        "--sort-keys",
+        action="store_true",
+        default=False,
+        help="sort the output of dictionaries alphabetically by key",
+    )
+    parser.add_argument(
+        "--json-lines",
+        "--yaml-lines",
+        action="store_true",
+        default=False,
+        help="parse input using the JSON Lines format. ",
+    )
+    group = parser.add_mutually_exclusive_group()
+    group.add_argument(
+        "--indent",
+        default=2,
+        type=int,
+        help="separate items with newlines and use this number "
+        "of spaces for indentation",
+    )
+    group.add_argument(
+        "--compact", action="store_true", help="suppress most whitespace separation",
+    )
+
+    options = parser.parse_args()
+
+    dump_args = {
+        "explicit_start": True,
+        "sort_keys": options.sort_keys,
+        "indent": options.indent,
+        "Dumper": SafeDumper,
+    }
+    if options.compact:
+        dump_args["explicit_start"] = False
+        dump_args["default_flow_style"] = True
+
+    with options.infile as infile:
+        try:
+            if options.json_lines:
+                objs = (yaml.load(line, Loader=SafeLoader) for line in infile)
+            else:
+                objs = yaml.load_all(infile, Loader=SafeLoader)
+
+            if options.outfile is None:
+                out = sys.stdout
+            else:
+                out = options.outfile.open("w", encoding="utf-8")
+            with out as outfile:
+                yaml.dump_all(objs, outfile, **dump_args)
+        except yaml.error.YAMLError as e:
+            raise SystemExit(e)
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except BrokenPipeError as exc:
+        sys.exit(exc.errno)