Improve jsonpointer CLI: support positional pointer argument

bin/jsonpointer

@@ -10,17 +10,21 @@ import jsonpointer
 parser = argparse.ArgumentParser(
     description='Resolve a JSON pointer on JSON files')
 
-# Accept pointer as argument or as file
-ptr_group = parser.add_mutually_exclusive_group(required=True)
+# Accept pointer as option, as file or as first positional argument
+ptr_group = parser.add_mutually_exclusive_group()
 
 ptr_group.add_argument('-f', '--pointer-file', type=argparse.FileType('r'),
                        nargs='?',
                        help='File containing a JSON pointer expression')
 
-ptr_group.add_argument('POINTER', type=str, nargs='?',
+ptr_group.add_argument('-p', '--pointer', type=str,
                        help='A JSON pointer expression')
 
-parser.add_argument('FILE', type=argparse.FileType('r'), nargs='+',
+parser.add_argument('POINTER', type=str, nargs='?',
+                    help='A JSON pointer expression (if neither -f nor -p '
+                         'is given)')
+
+parser.add_argument('FILE', type=str, nargs='+',
                     help='Files for which the pointer should be resolved')
 parser.add_argument('--indent', type=int, default=None,
                     help='Indent output by n spaces')
@@ -36,24 +40,49 @@ def main():
 
 
 def parse_pointer(args):
-    if args.POINTER:
+    """ Return the pointer and the list of files to resolve it on
+
+    If the pointer is given via -f or -p, a POINTER positional argument is
+    actually the first file. """
+    files = args.FILE
+
+    if args.pointer is not None or args.pointer_file is not None:
+        if args.POINTER is not None:
+            files = [args.POINTER] + files
+
+        if args.pointer is not None:
+            ptr = args.pointer
+        else:
+            ptr = args.pointer_file.read().strip()
+
+    elif args.POINTER is not None:
         ptr = args.POINTER
-    elif args.pointer_file:
-        ptr = args.pointer_file.read().strip()
+
     else:
-        parser.print_usage()
-        sys.exit(1)
+        parser.error('a JSON pointer is required (POINTER, -p or -f)')
+
+    # Catches e.g. `jsonpointer a.json b.json`, where the pointer was omitted
+    # and the first file would otherwise be used as the pointer
+    try:
+        jsonpointer.JsonPointer(ptr)
+    except jsonpointer.JsonPointerException as e:
+        parser.error('invalid JSON pointer %r: %s' % (ptr, e))
 
-    return ptr
+    return ptr, files
 
 
 def resolve_files():
     """ Resolve a JSON pointer on JSON files """
     args = parser.parse_args()
 
-    ptr = parse_pointer(args)
+    ptr, files = parse_pointer(args)
+
+    for name in files:
+        try:
+            f = argparse.FileType('r')(name)
+        except argparse.ArgumentTypeError as e:
+            parser.error(str(e))
 
-    for f in args.FILE:
         doc = json.load(f)
         try:
             result = jsonpointer.resolve_pointer(doc, ptr)

doc/commandline.rst

@@ -6,19 +6,28 @@ that can be used to resolve a JSON pointers on JSON files.
 
 The program has the following usage ::
 
-    usage: jsonpointer [-h] [--indent INDENT] [-v] POINTER FILE [FILE ...]
+    usage: jsonpointer [-h] [-f [POINTER_FILE] | -p POINTER] [--indent INDENT]
+                       [-v]
+                       [POINTER] FILE [FILE ...]
 
     Resolve a JSON pointer on JSON files
 
     positional arguments:
-      POINTER          File containing a JSON pointer expression
-      FILE             Files for which the pointer should be resolved
-
-    optional arguments:
-      -h, --help       show this help message and exit
-      --indent INDENT  Indent output by n spaces
-      -v, --version    show program's version number and exit
-
+      POINTER               A JSON pointer expression (if neither -f nor -p is
+                            given)
+      FILE                  Files for which the pointer should be resolved
+
+    options:
+      -h, --help            show this help message and exit
+      -f [POINTER_FILE], --pointer-file [POINTER_FILE]
+                            File containing a JSON pointer expression
+      -p POINTER, --pointer POINTER
+                            A JSON pointer expression
+      --indent INDENT       Indent output by n spaces
+      -v, --version         show program's version number and exit
+
+The pointer can be passed as the first positional argument, with ``-p``, or
+read from a file with ``-f``.
 
 Example
 ^^^^^^^
@@ -32,11 +41,20 @@ Example
     $ cat b.json
     { "a": {"b": [1, 3, 4]}, "b": 1 }
 
-    # inspect JSON pointer
-    $ cat ptr.json
-    "/a"
-
     # resolve JSON pointer
-    $ jsonpointer ptr.json a.json b.json
+    $ jsonpointer /a a.json b.json
+    [1, 2, 3]
+    {"b": [1, 3, 4]}
+
+    # same, using the -p option
+    $ jsonpointer -p /a a.json b.json
+    [1, 2, 3]
+    {"b": [1, 3, 4]}
+
+    # same, reading the pointer from a file
+    $ cat ptr.txt
+    /a
+
+    $ jsonpointer -f ptr.txt a.json b.json
     [1, 2, 3]
     {"b": [1, 3, 4]}

tests.py

@@ -2,7 +2,10 @@
 
 import copy
 import doctest
+import os
+import subprocess
 import sys
+import tempfile
 import unittest
 
 import jsonpointer
@@ -468,6 +471,87 @@ def test_mock_dict_raises_key_error(self):
         self.assertRaises(JsonPointerException, resolve_pointer, doc, '/root/1/2/3/4')
 
 
+class CommandLineTests(unittest.TestCase):
+    """ Tests the jsonpointer command line utility """
+
+    ROOT = os.path.dirname(os.path.abspath(__file__))
+    SCRIPT = os.path.join(ROOT, 'bin', 'jsonpointer')
+
+    A_OUT = '[1, 2, 3]\n'
+    B_OUT = '{"b": [1, 3, 4]}\n'
+
+    def setUp(self):
+        tmpdir = tempfile.TemporaryDirectory()
+        self.addCleanup(tmpdir.cleanup)
+        self.dir = tmpdir.name
+
+        self._write('a.json', '{ "a": [1, 2, 3] }')
+        self._write('b.json', '{ "a": {"b": [1, 3, 4]}, "b": 1 }')
+        self._write('ptr.txt', '/a\n')
+
+    def _write(self, name, content):
+        with open(os.path.join(self.dir, name), 'w') as f:
+            f.write(content)
+
+    def _run(self, *args):
+        env = dict(os.environ, PYTHONPATH=self.ROOT)
+        return subprocess.run([sys.executable, self.SCRIPT] + list(args),
+                              cwd=self.dir, env=env, capture_output=True,
+                              text=True)
+
+    def test_positional_pointer(self):
+        proc = self._run('/a', 'a.json', 'b.json')
+        self.assertEqual(proc.returncode, 0, proc.stderr)
+        self.assertEqual(proc.stdout, self.A_OUT + self.B_OUT)
+
+    def test_positional_pointer_single_file(self):
+        proc = self._run('/a', 'a.json')
+        self.assertEqual(proc.returncode, 0, proc.stderr)
+        self.assertEqual(proc.stdout, self.A_OUT)
+
+    def test_pointer_file(self):
+        proc = self._run('-f', 'ptr.txt', 'a.json', 'b.json')
+        self.assertEqual(proc.returncode, 0, proc.stderr)
+        self.assertEqual(proc.stdout, self.A_OUT + self.B_OUT)
+
+    def test_pointer_file_single_file(self):
+        proc = self._run('-f', 'ptr.txt', 'a.json')
+        self.assertEqual(proc.returncode, 0, proc.stderr)
+        self.assertEqual(proc.stdout, self.A_OUT)
+
+    def test_pointer_option(self):
+        proc = self._run('-p', '/a', 'a.json', 'b.json')
+        self.assertEqual(proc.returncode, 0, proc.stderr)
+        self.assertEqual(proc.stdout, self.A_OUT + self.B_OUT)
+
+    def test_no_pointer(self):
+        proc = self._run('a.json')
+        self.assertEqual(proc.returncode, 2)
+        self.assertIn('a JSON pointer is required', proc.stderr)
+
+    def test_missing_pointer_multiple_files(self):
+        proc = self._run('a.json', 'b.json')
+        self.assertEqual(proc.returncode, 2)
+        self.assertIn("invalid JSON pointer 'a.json'", proc.stderr)
+        self.assertEqual(proc.stdout, '')
+
+    def test_invalid_pointer_file(self):
+        self._write('bad.txt', 'a\n')
+        proc = self._run('-f', 'bad.txt', 'a.json')
+        self.assertEqual(proc.returncode, 2)
+        self.assertIn("invalid JSON pointer 'a'", proc.stderr)
+
+    def test_empty_pointer(self):
+        proc = self._run('', 'a.json')
+        self.assertEqual(proc.returncode, 0, proc.stderr)
+        self.assertEqual(proc.stdout, '{"a": [1, 2, 3]}\n')
+
+    def test_pointer_and_pointer_file_exclusive(self):
+        proc = self._run('-p', '/a', '-f', 'ptr.txt', 'a.json')
+        self.assertEqual(proc.returncode, 2)
+        self.assertIn('not allowed with', proc.stderr)
+
+
 class VerboseExceptionsTests(unittest.TestCase):
 
     def setUp(self):