Format custom help message with configured column width #413

amirsojoodi · 2023-12-03T21:58:09Z

Wrap the custom help message according to the column width.

This change is

jarro2783 · 2023-12-05T20:38:58Z

Can you write a unit test for this?

lazysegtree · 2025-12-27T05:20:09Z

@amirsojoodi Are you still working on this?

amirsojoodi · 2025-12-28T00:27:23Z

@lazysegtree I've forgotten about this. Give me some time, and I'll update

lazysegtree · 2025-12-29T18:40:41Z

test/options.cpp

+        "Custom message width A very very long description that \n  should "
+        "be wrapped according to the specified width for \n  help messages. "
+        "This is to ensure that lines are not very \n  long and remain "
+        "readable. Just to make sure we have \n  enough text here to trigger "
+        "the wrapping functionality \n  properly. Let's add a bit more text "
+        "to be certain!") != std::string::npos);


(0) Suggestion - Defining it like this will make the tests more readable and clear
Same for below

Suggested change

"Custom message width A very very long description that \n should "

"be wrapped according to the specified width for \n help messages. "

"This is to ensure that lines are not very \n long and remain "

"readable. Just to make sure we have \n enough text here to trigger "

"the wrapping functionality \n properly. Let's add a bit more text "

"to be certain!") != std::string::npos);

"Custom message width A very very long description that \n"

" should be wrapped according to the specified width for \n"

" help messages. This is to ensure that lines are not very \n"

" long and remain readable. Just to make sure we have \n"

" enough text here to trigger the wrapping functionality \n"

" properly. Let's add a bit more text "

"to be certain!") != std::string::npos);

I'll merge it with the formatting changes.

lazysegtree · 2025-12-30T03:08:58Z

While testing this I observed crash when there is a word that is bigger than the parameter passed to set_width.

I am gonna do a more thorough review and testing.

lazysegtree · 2025-12-30T06:56:57Z

include/cxxopts.hpp

    result += " " + toLocalString(m_custom_help);
+    result = format_custom_help(result, OPTION_DESC_GAP, m_width);


(1) @amirsojoodi This will fail in compilation for CXXOPTS_USE_UNICODE flag
For that we flag, we have using String = icu::UnicodeString;, and hence result here, will be of type icu::UnicodeString

format_custom_help only accepts std::string and wont allow icu::UnicodeString

Please fix that and ensure that we compile with that flag.

@jarro2783 We would need to fix the github CI, or we might cause regressions in the current code.
I hope we do test the compilation with CXXOPTS_USE_UNICODE in our CI

I am gonna give it a shot this weekend.

lazysegtree · 2025-12-30T07:04:56Z

include/cxxopts.hpp

+    throw_or_mimic<exceptions::invalid_option_format>("Allowed column" 
+      "width must be greater than start column width!");


(2) Typo
Missing concatanation of space in the error message
Should be

Suggested change

throw_or_mimic<exceptions::invalid_option_format>("Allowed column"

"width must be greater than start column width!");

throw_or_mimic<exceptions::invalid_option_format>("Allowed column "

"width must be greater than start column width!");

lazysegtree · 2025-12-30T07:08:41Z

include/cxxopts.hpp

+    }
+
+    // record the start of a word
+    word_size = (std::isspace(c)) ? 0 : word_size + 1;


(3) Please use bool isspace( CharT ch, const locale& loc )
Elsewhere in the library, we use locale specific checks. For example, check the usage of isalnum

lazysegtree · 2025-12-30T07:17:33Z

include/cxxopts.hpp

  return result;
 }

+String


(4) @amirsojoodi ~~the output sometimes contains extra unexpected lines that should not be appended~~

The output appends extra spaces when user gave only newlines.

options.custom_help("This is a multiline custom help\nLine2\n\nLine4");

I think, this should ideally show something like this

3 │ ····checker·This·is·a·multiline·custom·help␊ 4 │ ··Line2␊ 5 │ ␊ 6 │ ··Line4␊ 7 │ ␊

But its actually this right now

➜ ~/Workspace/Other_proj/cxxopts-amir/include git:(patch-2) ✗ [9:02:28] g++ main.cpp && ./a.out -h | bat --show-all --no-pager ───────┬─────────────────────────────────────────────────────────────────────────────────────────────── │ STDIN ───────┼─────────────────────────────────────────────────────────────────────────────────────────────── 1 │ ··Test·cxxopts␊ 2 │ ··Usage:␊ 3 │ ····checker·This·is·a·multiline·custom·help␊ 4 │ ··Line2␊ 5 │ ··␊ 6 │ ··Line4␊ 7 │ ␊ 8 │ ··-d,·--debug2·······01234567890123456789␊ 9 │ ··-i,·--integer·arg··Int·param␊ 10 │ ··-f,·--file·arg·····File·name␊ 11 │ ··-v,·--verbose······Verbose·output␊ 12 │ ··-h,·--help·········Print·usage␊ 13 │ ␊ ───────┴─────────────────────────────────────────────────────────────────────────────────────────────── ➜ ~/Workspace/Other_proj/cxxopts-amir/include git:(patch-2) ✗ [9:03:01]

This is almost unnoticeable to the user, but is a slightly unexepected behaviour in my opinion.

lazysegtree · 2025-12-30T07:21:47Z

include/cxxopts.hpp

  return result;
 }

+String


(5) If options.set_width is called with a low value like 10, and there is a word of greater length. THe program gets stuck in infinite loop.

There may be long URLs in the help, so we need to handle words of very long length

lazysegtree · 2025-12-30T07:24:28Z

test/options.cpp

  CHECK(options.help().find("test <posArg1>...<posArgN>") != std::string::npos);
 }
+
+TEST_CASE("Format custom message with selected width", "[help]")


(6) Test cases are lacking a lot of checks. Please ensure that they cover most of the issues above.

Please also include a test for throwing exceptions::invalid_option_format on setting too less width.

lazysegtree · 2025-12-30T07:26:52Z

include/cxxopts.hpp

+
+  if(allowed <= start)
+  {
+    throw_or_mimic<exceptions::invalid_option_format>("Allowed column" 


(7) With current code, the exception will only get thrown when users use -h, while the trigger was the user setting wrong value in options.set_width

The exception should be thrown at the time of set_width.

We should be throwing exceptions when users set an invalid configuration, not when they attempt to use that invalid config.
What do you think @jarro2783

# code with `options.set_width(1);` in main.cpp. # If users don't test -h, they will not know of the misconfig. ➜ ~/Workspace/Other_proj/cxxopts-amir/include git:(patch-2) ✗ [12:50:12] g++ main.cpp && ./a.out -h start Invalid option format 'Allowed columnwidth must be greater than start column width!' ➜ ~/Workspace/Other_proj/cxxopts-amir/include git:(patch-2) ✗ [12:54:39] g++ main.cpp && ./a.out start help = false (default) verbose = false (default) debug2 = false (default) ➜ ~/Workspace/Other_proj/cxxopts-amir/include git:(patch-2) ✗ [12:54:44]

lazysegtree

@amirsojoodi Can you please fix comment 0-7. If some of them are not valid, and need further discussion, let me know.

lazysegtree · 2026-01-01T03:45:51Z

include/cxxopts.hpp

  if (!m_custom_help.empty())
  {
    result += " " + toLocalString(m_custom_help);
+    result = format_custom_help(result, OPTION_DESC_GAP, m_width);


(8) At this point, you are formatting the entire results that also contains Main program help -> m_help_string .

Since your function is named format_custom_help, I think that is not the intention here. You only intend to format the custom help part.

Right now even the main help is getting formatted.

cxxopts::Options options("checker", "Test cxxopts with a very very very very very long program description"); options.custom_help(" 123456789 123456789 123456789 123456789 123456789"); options.add_options() ("h,help", "Print usage") ; options.set_width(30);

➜ ~/Workspace/Other_proj/cxxopts-amir/include git:(patch-2) ✗ [9:12:01] g++ main.cpp && ./a.out -h | bat --show-all --no-pager ───────┬─────────────────────────────────────────────────────────────────────────────────────────────── │ STDIN ───────┼─────────────────────────────────────────────────────────────────────────────────────────────── 1 │ ··Test·cxxopts·with·a·very·␊ 2 │ ··very·very·very·very·long·␊ 3 │ ··program·description␊ 4 │ ··Usage:␊ 5 │ ····checker··123456789·␊ 6 │ ··123456789·123456789·␊ 7 │ ··123456789·123456789␊ 8 │ ␊ 9 │ ··-h,·--help··Print·usage␊ 10 │ ␊ ───────┴─────────────────────────────────────────────────────────────────────────────────────────────── ➜ ~/Workspace/Other_proj/cxxopts-amir/include git:(patch-2) ✗ [9:14:48]

So either you should only format the custom help part, or use the function irrespective of m_custom_help being empty or not, and name it to wrap_help or something generic.

@jarro2783 What do you think our output should be in this case

cxxopts::Options options("checker", "Test cxxopts with a very very very very very long program description"); options.custom_help(" 123456789 123456789 123456789 123456789 123456789"); options.add_options() ("h,help", "Print usage"); options.set_width(30);

(a) This

1 │ ··Test·cxxopts·with·a·very·␊ 2 │ ··very·very·very·very·long·␊ 3 │ ··program·description␊ 4 │ ··Usage:␊ 5 │ ····checker··123456789·␊ 6 │ ··123456789·123456789·␊ 7 │ ··123456789·123456789␊ 8 │ ␊ 9 │ ··-h,·--help··Print·usage␊ 10 │ ␊

(b) Or this

1 │ Test·cxxopts·with·a·very·very·very·very·very·long·program·description␊ 2 │ Usage:␊ 3 │ ··checker····123456789·123456789·␊ 4 │ ··123456789·123456789·␊ 5 │ ··123456789␊ 6 │ ␊ 7 │ ··-h,·--help··Print·usage␊ 8 │ ␊

jarro2783 · 2026-01-01T04:43:00Z

I think it would be more intuitive that all of the help gets formatted when you call set_width.

jarro2783 · 2026-01-01T05:10:15Z

If you rebase on master we will have working CI now.

amirsojoodi force-pushed the patch-2 branch 2 times, most recently from a638577 to 3945f84 Compare December 29, 2025 03:56

amirsojoodi added 2 commits December 29, 2025 01:23

Format custom help message with configured column width

ae1c3ca

Add unit test for customized width for help

2f7f449

amirsojoodi force-pushed the patch-2 branch from 3945f84 to 2f7f449 Compare December 29, 2025 06:24

lazysegtree reviewed Dec 29, 2025

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lazysegtree reviewed Jan 1, 2026

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lazysegtree mentioned this pull request Jan 7, 2026

Add Meson buildsystem support #424

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		result += " " + toLocalString(m_custom_help);
		result = format_custom_help(result, OPTION_DESC_GAP, m_width);

		throw_or_mimic<exceptions::invalid_option_format>("Allowed column"
		"width must be greater than start column width!");

Format custom help message with configured column width #413

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Format custom help message with configured column width #413

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