add "piccolo user list" command

docs/src/piccolo/authentication/baseuser.rst

@@ -44,6 +44,11 @@ script), you can pass all of the arguments in as follows:
    If you choose this approach then be careful, as the password will be in the
    shell's history.
 
+list
+~~~~
+
+List existing users.
+
 change_password
 ~~~~~~~~~~~~~~~
 

piccolo/apps/user/commands/list.py

@@ -0,0 +1,15 @@
+from piccolo.apps.user.tables import BaseUser
+from piccolo.utils.printing import print_dict_table
+
+
+def list():
+    """
+    List existing users.
+    """
+    users = (
+        BaseUser.select(BaseUser.all_columns(exclude=[BaseUser.password]))
+        .order_by(BaseUser.username)
+        .run_sync()
+    )
+
+    print_dict_table(users)

piccolo/apps/user/piccolo_app.py

@@ -5,6 +5,7 @@
 from .commands.change_password import change_password
 from .commands.change_permissions import change_permissions
 from .commands.create import create
+from .commands.list import list
 from .tables import BaseUser
 
 CURRENT_DIRECTORY = os.path.dirname(os.path.abspath(__file__))
@@ -19,6 +20,7 @@
     migration_dependencies=[],
     commands=[
         Command(callable=create, aliases=["new"]),
+        Command(callable=list, aliases=["ls"]),
         Command(callable=change_password, aliases=["password", "pass"]),
         Command(callable=change_permissions, aliases=["perm", "perms"]),
     ],

piccolo/utils/printing.py

@@ -1,3 +1,6 @@
+from typing import List
+
+
 def get_fixed_length_string(string: str, length=20) -> str:
     """
     Add spacing to the end of the string so it's a fixed length, or truncate
@@ -16,3 +19,36 @@ def print_heading(string: str, width: int = 64) -> None:
     """
     print(f"\n{string.upper():^{width}}")
     print("-" * width)
+
+
+def print_dict_table(data: List[dict], header_separator: bool = False) -> None:
+    """
+    Prints out a list of dictionaries in tabular form.
+    Uses the first list element to extract the
+    column names and their order within the row.
+    """
+
+    if len(data) < 1:
+        print("No data")
+        return
+
+    ref_order = [column for column in data[0]]
+    width = {column: len(str(column)) for column in ref_order}
+
+    for item in data:
+        for column in ref_order:
+            if len(str(item[column])) > width[column]:
+                width[column] = len(str(item[column]))
+
+    format_string = " | ".join([f"{{:<{width[w]}}}" for w in ref_order])
+
+    print(format_string.format(*[str(w) for w in ref_order]))
+
+    if header_separator:
+        format_string_sep = "-+-".join(
+            [f"{{:<{width[w]}}}" for w in ref_order]
+        )
+        print(format_string_sep.format(*["-" * width[w] for w in ref_order]))
+
+    for item in data:
+        print(format_string.format(*[str(item[w]) for w in ref_order]))