Add meson test --max-lines

Let's allow users to configure how many lines are shown at most when
a test fails.

data/shell-completions/bash/meson

@@ -580,6 +580,7 @@ _meson-test() {
     quiet
     timeout-multiplier
     setup
+    max-lines
     test-args
   )
 

data/shell-completions/zsh/_meson

@@ -196,6 +196,7 @@ local -a meson_commands=(
   '(--quiet -q)'{'--quiet','-q'}'[produce less output to the terminal]'
   '(--timeout-multiplier -t)'{'--timeout-multiplier','-t'}'[a multiplier for test timeouts]:Python floating-point number: '
   '--setup[which test setup to use]:test setup: '
+  '--max-lines[Maximum number of lines to show from a long test log]:Python integer number: '
   '--test-args[arguments to pass to the tests]: : '
   '*:Meson tests:__meson_test_names'
   )

docs/markdown/Unit-tests.md

@@ -274,6 +274,14 @@ other useful information as the environmental variables. This is
 useful, for example, when you run the tests on Travis-CI, Jenkins and
 the like.
 
+By default, the output from tests will be limited to the last 100 lines. The
+maximum number of lines to show can be configured with the `--max-lines` option
+*(added 1.5.0)*:
+
+```console
+$ meson test --max-lines=1000 testname
+```
+
 **Timeout**
 
 In the test case options, the `timeout` option is specified in a number of seconds.

docs/markdown/snippets/test_max_lines.md

@@ -0,0 +1,6 @@
+## The Meson test program supports a new "--max-lines" argument
+
+By default `meson test` only shows the last 100 lines of test output from tests
+that produce large amounts of output. This default can now be changed with the
+new `--max-lines` option. For example, `--max-lines=1000` will increase the
+maximum number of log output lines from 100 to 1000.

mesonbuild/mtest.py

@@ -161,6 +161,8 @@ def add_arguments(parser: argparse.ArgumentParser) -> None:
                         help='Which test setup to use.')
     parser.add_argument('--test-args', default=[], type=split_args,
                         help='Arguments to pass to the specified test(s) or all tests')
+    parser.add_argument('--max-lines', default=100, dest='max_lines', type=int,
+                        help='Maximum number of lines to show from a long test log. Since 1.5.0.')
     parser.add_argument('args', nargs='*',
                         help='Optional list of test names to run. "testname" to run all tests with that name, '
                         '"subprojname:testname" to specifically run "testname" from "subprojname", '
@@ -510,7 +512,8 @@ class ConsoleLogger(TestLogger):
     HLINE = "\u2015"
     RTRI = "\u25B6 "
 
-    def __init__(self) -> None:
+    def __init__(self, max_lines: int) -> None:
+        self.max_lines = max_lines
         self.running_tests: OrderedSet['TestRun'] = OrderedSet()
         self.progress_test: T.Optional['TestRun'] = None
         self.progress_task: T.Optional[asyncio.Future] = None
@@ -652,10 +655,10 @@ def shorten_log(self, harness: 'TestHarness', result: 'TestRun') -> str:
             return log
 
         lines = log.splitlines()
-        if len(lines) < 100:
+        if len(lines) < self.max_lines:
             return log
         else:
-            return str(mlog.bold('Listing only the last 100 lines from a long log.\n')) + '\n'.join(lines[-100:])
+            return str(mlog.bold(f'Listing only the last {self.max_lines} lines from a long log.\n')) + '\n'.join(lines[-self.max_lines:])
 
     def print_log(self, harness: 'TestHarness', result: 'TestRun') -> None:
         if not result.verbose:
@@ -1591,7 +1594,7 @@ def __init__(self, options: argparse.Namespace):
         self.name_max_len = 0
         self.is_run = False
         self.loggers: T.List[TestLogger] = []
-        self.console_logger = ConsoleLogger()
+        self.console_logger = ConsoleLogger(options.max_lines)
         self.loggers.append(self.console_logger)
         self.need_console = False
         self.ninja: T.List[str] = None