Add tests and better user warnings

• Better warnings using (built-in)[https://docs.python.org/3/library/warnings.html] `warnings` module when `colalign` or `headersalign` is a `string`. Warnings are now directed to `stderr`.
• Added `check_warning` tool to `test/common.py`.
• Added following tests:
- `test_column_global_and_specific_alignment`
- `test_headers_global_and_specific_alignment`
- `test_colalign_or_headersalign_too_long`
- `test_warning_when_colalign_or_headersalign_is_string`

Author: eliegoudout

tabulate/__init__.py

@@ -1,5 +1,6 @@
 """Pretty-print tabular data."""
 
+import warnings
 from collections import namedtuple
 from collections.abc import Iterable, Sized
 from html import escape as htmlescape
@@ -2209,8 +2210,7 @@ def tabulate(
     if colalign is not None:
         assert isinstance(colalign, Iterable)
         if isinstance(colalign, str):
-            print(
-                f"Warning in `tabulate`: As a string, `colalign` is interpreted as {[c for c in colalign]}. Did you mean `colglobalalign = \"{colalign}\"` or `colalign = (\"{colalign}\",)`?")
+            warnings.warn(f"As a string, `colalign` is interpreted as {[c for c in colalign]}. Did you mean `colglobalalign = \"{colalign}\"` or `colalign = (\"{colalign}\",)`?", stacklevel=2)
         for idx, align in enumerate(colalign):
             if not idx < len(aligns):
                 break
@@ -2237,8 +2237,7 @@ def tabulate(
         if headersalign is not None:
             assert isinstance(headersalign, Iterable)
             if isinstance(headersalign, str):
-                print(
-                    f"Warning in `tabulate`: As a string, `headersalign` is interpreted as {[c for c in headersalign]}. Did you mean `headersglobalalign = \"{headersalign}\"` or `headersalign = (\"{headersalign}\",)`?")
+                warnings.warn(f"As a string, `headersalign` is interpreted as {[c for c in headersalign]}. Did you mean `headersglobalalign = \"{headersalign}\"` or `headersalign = (\"{headersalign}\",)`?", stacklevel=2)
             for idx, align in enumerate(headersalign):
                 hidx = headers_pad + idx
                 if not hidx < len(aligns_headers):

test/common.py

@@ -1,6 +1,6 @@
 import pytest  # noqa
 from pytest import skip, raises  # noqa
-
+import warnings
 
 def assert_equal(expected, result):
     print("Expected:\n%s\n" % expected)
@@ -27,3 +27,18 @@ def rows_to_pipe_table_str(rows):
         lines.append(line)
 
     return "\n".join(lines)
+
+def check_warnings(func_args_kwargs, *, num=None, category=None, contain=None):
+    func, args, kwargs = func_args_kwargs
+    with warnings.catch_warnings(record=True) as W:
+        # Causes all warnings to always be triggered inside here.
+        warnings.simplefilter("always")
+        func(*args, **kwargs)
+        # Checks
+        if num is not None:
+            assert len(W) == num
+        if category is not None:
+            assert all([issubclass(w.category, category) for w in W])
+        if contain is not None:
+            assert all([contain in str(w.message) for w in W])
+

test/test_output.py

@@ -1,7 +1,7 @@
 """Test output of the various forms of tabular data."""
 
 import tabulate as tabulate_module
-from common import assert_equal, raises, skip
+from common import assert_equal, raises, skip, check_warnings
 from tabulate import tabulate, simple_separated_format, SEPARATING_LINE
 
 # _test_table shows
@@ -2680,6 +2680,60 @@ def test_colalign_multi_with_sep_line():
     expected = "  one  two\n\nthree  four"
     assert_equal(expected, result)
 
+def test_column_global_and_specific_alignment():
+    """ Test `colglobalalign` and `"global"` parameter for `colalign`. """
+    table = [[1,2,3,4],[111,222,333,444]]
+    colglobalalign = 'center'
+    colalign = ('global','left', 'right')
+    result = tabulate(table, colglobalalign=colglobalalign, colalign=colalign)
+    expected = '\n'.join([
+        "---  ---  ---  ---",
+        " 1   2      3   4",
+        "111  222  333  444",
+        "---  ---  ---  ---"])
+    assert_equal(expected, result)
+
+def test_headers_global_and_specific_alignment():
+    """ Test `headersglobalalign` and `headersalign`. """
+    table = [[1,2,3,4,5,6],[111,222,333,444,555,666]]
+    colglobalalign = 'center'
+    colalign = ('left',)
+    headers = ['h', 'e', 'a', 'd', 'e', 'r']
+    headersglobalalign = 'right'
+    headersalign = ('same', 'same', 'left', 'global', 'center')
+    result = tabulate(table, headers=headers, colglobalalign=colglobalalign, colalign=colalign, headersglobalalign=headersglobalalign, headersalign=headersalign)
+    expected = '\n'.join([
+        "h     e   a      d   e     r",
+        "---  ---  ---  ---  ---  ---",
+        "1     2    3    4    5    6",
+        "111  222  333  444  555  666"])
+    assert_equal(expected, result)
+
+def test_colalign_or_headersalign_too_long():
+    """ Test `colalign` and `headersalign` too long. """
+    table = [[1,2],[111,222]]
+    colalign = ('global', 'left', 'center')
+    headers = ['h']
+    headersalign = ('center', 'right', 'same')
+    result = tabulate(table, headers=headers, colalign=colalign, headersalign=headersalign)
+    expected = '\n'.join([
+        "      h",
+        "---  ---",
+        "  1  2",
+        "111  222"])
+    assert_equal(expected, result)
+
+def test_warning_when_colalign_or_headersalign_is_string():
+    """ Test user warnings when `colalign` or `headersalign` is a string. """
+    table = [[1,"bar"]]
+    opt = {
+        'colalign': "center",
+        'headers': ['foo', '2'],
+        'headersalign': "center"}
+    check_warnings((tabulate, [table], opt),
+        num = 2,
+        category = UserWarning,
+        contain = "As a string")
 
 def test_float_conversions():
     "Output: float format parsed"