When configuring fails in Github Actions, print folded logs

A common, and challenging, issue in CI runners is debugging issues when
you know the information you want to check, but it's in the log file
which you don't have because remote CI machines.

There are various edge cases where this is especially hard to solve,
such as inside of `pip install` where the build directory with the log
file is automatically cleaned up. But it's never really *easy* when you
don't expect it, and the best case scenario is your iteration time gets
cut in half as you hurriedly go add some `cat`s to your CI scripts.

Meson can, at least sometimes, detect platforms where text can be
emitted inside of "folds", which are auto-collapsed and don't obscure
the general output, but when clicked will expand the logfile contents.
Hook this up.

We start off with a Github Actions implementation. We had some internal
code used by our own project tests runner, which can be utilized.

Also permit forcing it via an environment variable, in case
autodetection fails and you just want to force *something*, especially
when meson is called a couple layers deep inside some other tool.

1 files changed, 30 insertions, 1 deletions

diff --git a/mesonbuild/mlog.py b/mesonbuild/mlog.py
index a8b018537..bc8faeba7 100644
--- a/mesonbuild/mlog.py
+++ b/mesonbuild/mlog.py
@@ -22,8 +22,9 @@ from dataclasses import dataclass, field
 from pathlib import Path
 
 if T.TYPE_CHECKING:
-    from ._typing import StringProtocol, SizedStringProtocol
+    from typing_extensions import Literal
 
+    from ._typing import StringProtocol, SizedStringProtocol
     from .mparser import BaseNode
 
     TV_Loggable = T.Union[str, 'AnsiDecorator', StringProtocol]
@@ -75,6 +76,7 @@ def setup_console() -> None:
             pass
 
 _in_ci = 'CI' in os.environ
+_ci_is_github = 'GITHUB_ACTIONS' in os.environ
 
 
 class _Severity(enum.Enum):
@@ -540,3 +542,30 @@ def code_line(text: str, line: str, colno: int) -> str:
     :return: A formatted string of the text, line, and a caret
     """
     return f'{text}\n{line}\n{" " * colno}^'
+
+@T.overload
+def ci_fold_file(fname: T.Union[str, os.PathLike], banner: str, force: Literal[True] = True) -> str: ...
+
+@T.overload
+def ci_fold_file(fname: T.Union[str, os.PathLike], banner: str, force: Literal[False] = False) -> T.Optional[str]: ...
+
+def ci_fold_file(fname: T.Union[str, os.PathLike], banner: str, force: bool = False) -> T.Optional[str]:
+    if not _in_ci and not force:
+        return None
+
+    if _ci_is_github:
+        header = f'::group::==== {banner} ===='
+        footer = '::endgroup::'
+    elif force:
+        header = banner
+        footer = ''
+    elif 'MESON_FORCE_SHOW_LOGS' in os.environ:
+        header = f'==== Forcing display of logs for {os.path.basename(fname)} ===='
+        footer = ''
+    else:
+        # only github is implemented
+        return None
+
+    with open(fname, 'r', encoding='utf-8') as f:
+        data = f.read()
+    return f'{header}\n{data}\n{footer}\n'