Fix #354: a header that fits in maxcolwidths must not widen the column

tabulate/__init__.py

@@ -2386,6 +2386,14 @@ def tabulate(
             elif align != "global":
                 aligns[idx] = align
     minwidths = [width_fn(h) + min_padding for h in headers] if headers else [0] * len(cols)
+    # A header that fits inside an explicit maxcolwidths must not push the column
+    # past that limit: the extra header padding would be rendered as unwanted
+    # whitespace (#354). Headers that are wider than the limit keep the previous
+    # behaviour, so the table stays aligned; `maxheadercolwidths` wraps those.
+    if headers and maxcolwidths and len(headers) == len(cols):
+        for i, cap in enumerate(maxcolwidths[: len(minwidths)]):
+            if cap and width_fn(headers[i]) <= cap:
+                minwidths[i] = min(minwidths[i], cap)
     aligns_copy = aligns.copy()
     # Reset alignments in copy of alignments list to "left" for 'colon_grid' format,
     # which enforces left alignment in the text output of the data.

test/test_output.py

@@ -149,6 +149,13 @@ def test_plain_maxcolwidth_autowraps_wide_chars():
     assert_equal(expected, result)
 
 
+def test_maxcolwidth_header_does_not_add_padding():
+    "Output: a header that fits inside maxcolwidths does not widen the column (#354)"
+    expected = "\n".join(["+-----+", "| foo |", "+=====+", "| bar |", "+-----+"])
+    result = tabulate([["foo"], ["bar"]], headers="firstrow", tablefmt="grid", maxcolwidths=3)
+    assert_equal(expected, result)
+
+
 def test_maxcolwidth_single_value():
     "Output: maxcolwidth can be specified as a single number that works for each column"
     table = [
@@ -157,11 +164,11 @@ def test_maxcolwidth_single_value():
     ]
     expected = "\n".join(
         [
-            "hdr    fold1    fold2",
-            "mini   this     this",
-            "       is       is a",
-            "       short    bit",
-            "                longer",
+            "hdr    fold1   fold2",
+            "mini   this    this",
+            "       is      is a",
+            "       short   bit",
+            "               longer",
         ]
     )
     result = tabulate(table, headers="firstrow", tablefmt="plain", maxcolwidths=6)
@@ -176,8 +183,8 @@ def test_maxcolwidth_pad_tailing_widths():
     ]
     expected = "\n".join(
         [
-            "hdr    fold1    fold2",
-            "mini   this     this is a bit longer",
+            "hdr    fold1   fold2",
+            "mini   this    this is a bit longer",
             "       is",
             "       short",
         ]
@@ -3325,13 +3332,14 @@ def test_break_long_words():
     table_headers = ["h1", "h2", "h3"]
     test_table = [["  foo1", " bar2   ", "foo3"]]
 
-    # Table is not wrapped on 3 letters due to long word
+    # Long words are not broken, so the column keeps the width of the word itself
     expected = "h1    h2    h3\n----  ----  ----\nfoo1  bar2  foo3"
     result = tabulate(test_table, table_headers, maxcolwidths=3, break_long_words=False)
     assert_equal(expected, result)
 
-    # Table max width is 3 letters
-    expected = "h1    h2    h3\n----  ----  ----\nf     ba    foo\noo1   r2    3"
+    # Table max width is 3 letters; the header is shorter than the limit, so it
+    # must not add its 2 spaces of padding on top of the limit (#354)
+    expected = "h1   h2   h3\n---  ---  ---\nf    ba   foo\noo1  r2   3"
     result = tabulate(test_table, table_headers, maxcolwidths=3, break_long_words=True)
     assert_equal(expected, result)
 

test/test_textwrapper.py

@@ -240,19 +240,19 @@ def test_wrap_datetime():
     result = tabulate(data, headers=headers, tablefmt="grid", maxcolwidths=[7, 5])
 
     expected = [
-        "+---------+--------+",
-        "| Title   | When   |",
-        "+=========+========+",
-        "| First   | 2020-  |",
-        "| Entry   | 01-01  |",
-        "|         | 05:06  |",
-        "|         | :07    |",
-        "+---------+--------+",
-        "| Second  | 2021-  |",
-        "| Entry   | 02-02  |",
-        "|         | 00:00  |",
-        "|         | :00    |",
-        "+---------+--------+",
+        "+---------+-------+",
+        "| Title   | When  |",
+        "+=========+=======+",
+        "| First   | 2020- |",
+        "| Entry   | 01-01 |",
+        "|         | 05:06 |",
+        "|         | :07   |",
+        "+---------+-------+",
+        "| Second  | 2021- |",
+        "| Entry   | 02-02 |",
+        "|         | 00:00 |",
+        "|         | :00   |",
+        "+---------+-------+",
     ]
     expected = "\n".join(expected)
     assert_equal(expected, result)
@@ -265,15 +265,15 @@ def test_wrap_none_value():
     result = tabulate(data, headers=headers, tablefmt="grid", maxcolwidths=[7, 5])
 
     expected = [
-        "+---------+---------+",
-        "| Title   | Value   |",
-        "+=========+=========+",
-        "| First   |         |",
-        "| Entry   |         |",
-        "+---------+---------+",
-        "| Second  |         |",
-        "| Entry   |         |",
-        "+---------+---------+",
+        "+---------+-------+",
+        "| Title   | Value |",
+        "+=========+=======+",
+        "| First   |       |",
+        "| Entry   |       |",
+        "+---------+-------+",
+        "| Second  |       |",
+        "| Entry   |       |",
+        "+---------+-------+",
     ]
     expected = "\n".join(expected)
     assert_equal(expected, result)
@@ -288,15 +288,15 @@ def test_wrap_none_value_with_missingval():
     )
 
     expected = [
-        "+---------+---------+",
-        "| Title   | Value   |",
-        "+=========+=========+",
-        "| First   | ???     |",
-        "| Entry   |         |",
-        "+---------+---------+",
-        "| Second  | ???     |",
-        "| Entry   |         |",
-        "+---------+---------+",
+        "+---------+-------+",
+        "| Title   | Value |",
+        "+=========+=======+",
+        "| First   | ???   |",
+        "| Entry   |       |",
+        "+---------+-------+",
+        "| Second  | ???   |",
+        "| Entry   |       |",
+        "+---------+-------+",
     ]
     expected = "\n".join(expected)
     assert_equal(expected, result)
@@ -312,15 +312,15 @@ def test_wrap_optional_bool_strs():
     result = tabulate(data, headers=headers, tablefmt="grid", maxcolwidths=[7, 5])
 
     expected = [
-        "+---------+--------+",
-        "| Title   | When   |",
-        "+=========+========+",
-        "| First   | True   |",
-        "| Entry   |        |",
-        "+---------+--------+",
-        "| Second  |        |",
-        "| Entry   |        |",
-        "+---------+--------+",
+        "+---------+-------+",
+        "| Title   | When  |",
+        "+=========+=======+",
+        "| First   | True  |",
+        "| Entry   |       |",
+        "+---------+-------+",
+        "| Second  |       |",
+        "| Entry   |       |",
+        "+---------+-------+",
     ]
     expected = "\n".join(expected)
     assert_equal(expected, result)

test_354_acceptance.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python3
+"""python-tabulate #354 的验收（可执行断言，不是形容词）。
+
+用法：在 python-tabulate 的 clone 根目录跑
+    PYTHONPATH=. python3 test_354_acceptance.py
+全部 PASS 退出码 0；有 FAIL 退出码 1。改前应当看见 A 是红的。
+"""
+import sys
+
+from tabulate import _wrap_text_to_colwidths, tabulate
+
+CELL = "The files were concatenated and archived for posterity."
+
+
+def cell_width(header, w):
+    """渲染出来那一格的内容宽（去掉 fancy_grid 两侧各一个空格）。"""
+    t = tabulate([[CELL]], headers=[header], tablefmt="fancy_grid", maxcolwidths=[w])
+    lines = [l for l in t.splitlines() if l.startswith("\u2502")]
+    cell = lines[1].split("\u2502")[1]
+    return len(cell) - 2
+
+
+def check(name, got, want):
+    ok = got == want
+    print(("PASS " if ok else "FAIL ") + "{}: 实测={} 期望={}".format(name, got, want))
+    return ok
+
+
+def main():
+    results = []
+
+    # A：表头 8 字、上限 8 → 内容宽必须是 8。
+    #    改前实测 10（单元格宽 12），这就是 #354 的偏差本身。
+    results.append(check("A 表头 Header#3 + maxcolwidths=8", cell_width("Header#3", 8), 8))
+
+    # B：表头比上限短时本来就对。用来证明缺陷跟表头长度有关，不是折行。
+    results.append(check("B 表头 h1 + maxcolwidths=8", cell_width("h1", 8), 8))
+
+    # C：数据格的折行不许被改动（上限就是上限，最长行必须等于 8）。
+    #    它是护栏：谁去“修” TextWrapper，这条就会红。
+    wrapped = _wrap_text_to_colwidths([[CELL]], [8])[0][0]
+    longest = max(len(line) for line in wrapped.split("\n"))
+    results.append(check("C 折行最长行 <= 上限", longest, 8))
+
+    print("---")
+    print("结论：{}".format("全部通过" if all(results) else "有 FAIL，别提交补丁"))
+    return 0 if all(results) else 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())