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.

mesonbuild/mesonmain.py

@@ -26,6 +26,9 @@ def errorhandler(e, command):
         logfile = mlog.shutdown()
         if logfile is not None:
             mlog.log("\nA full log can be found at", mlog.bold(logfile))
+            contents = mlog.ci_fold_file(logfile, 'CI platform detected, click here for log contents.')
+            if contents:
+                print(contents)
         if os.environ.get('MESON_FORCE_BACKTRACE'):
             raise e
         return 1

mesonbuild/mlog.py

@@ -75,6 +75,7 @@ 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 +541,21 @@ 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}^'
+
+def ci_fold_file(fname: T.Union[str, os.PathLike], banner: T.Optional[str]) -> T.Optional[str]:
+    if not _in_ci:
+        return None
+
+    if not banner:
+        banner = os.fsdecode(fname)
+
+    if _ci_is_github:
+        header = f'::group::==== {banner} ===='
+        footer = '::endgroup::'
+    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'

run_project_tests.py

@@ -301,7 +301,6 @@ def __lt__(self, other: object) -> bool:
 failing_logs: T.List[str] = []
 print_debug = 'MESON_PRINT_TEST_OUTPUT' in os.environ
 under_ci = 'CI' in os.environ
-ci_is_github = 'GITHUB_ACTIONS' in os.environ
 raw_ci_jobname = os.environ.get('MESON_CI_JOBNAME', None)
 ci_jobname = raw_ci_jobname if raw_ci_jobname != 'thirdparty' else None
 do_debug = under_ci or print_debug
@@ -433,16 +432,12 @@ def log_text_file(logfile: T.TextIO, testdir: Path, result: TestResult) -> None:
 
 
 def _run_ci_include(args: T.List[str]) -> str:
-    header = f'Included file {args[0]}:'
-    footer = ''
-    if ci_is_github:
-        header = f'::group::==== {header} ===='
-        footer = '::endgroup::'
     if not args:
         return 'At least one parameter required'
+
+    header = f'Included file {args[0]}:'
     try:
-        data = Path(args[0]).read_text(errors='ignore', encoding='utf-8')
-        return f'{header}\n{data}\n{footer}\n'
+        mlog.ci_fold_log(args[0], header)
     except Exception:
         return 'Failed to open {}\n'.format(args[0])