[lit] RUN commands without stdin.

[csigg]

Summary

This changes the initial stdin of a lit RUN command to be None, so that tools taking input from stdin do not see a zero-length input.

This will prevent issues like that one fixed in commit 720dd81.

[probinson]

So what would such a tool see? Would it get an error trying to open stdin, or something else?

Needs a test in lit's own test suite.

[csigg]

Add test, fix external shell mode.

[csigg]

Fix bazel config to actually test lit tests.

Create a separate test instead of reusing the shtest-timeout one.

[csigg]

In D135067#3830815, @probinson wrote:

So what would such a tool see? Would it get an error trying to open stdin, or something else?

A tool reading from stdin would get stdin, not an error and not an empty string (which it did before this change).

Needs a test in lit's own test suite.

Done.

[probinson]

In D135067#3832848, @csigg wrote:

In D135067#3830815, @probinson wrote:

So what would such a tool see? Would it get an error trying to open stdin, or something else?

A tool reading from stdin would get stdin, not an error and not an empty string (which it did before this change).

Ah. I interpreted that to mean "it will hang waiting for input" and then I see the test expects lit to timeout the test. That works.

LGTM

[csigg]

Fix clang tests that relied on empty input or accidentally did not provide the input in the RUN directive.

[jhenderson]

llvm/utils/lit/tests/Inputs/shtest-stdin/print-stdin.py

6 ↗

(On Diff #465096)

Nit: add newline at EOF.

llvm/utils/lit/tests/shtest-stdin.py

28 ↗

(On Diff #465096)

Nit: Don't have multiple \n at EOF (there should be exactly one).

llvm/utils/lit/lit/TestRunner.py

if isinstance(cmd, ShUtil.Seq):
                 res = _executeShCmd(cmd.rhs, shenv, results, timeoutHelper)
             return res
 
         raise ValueError('Unknown shell command: %r' % cmd.op)
     assert isinstance(cmd, ShUtil.Pipeline)
 
     procs = []
     proc_not_counts = []
-    default_stdin = subprocess.PIPE
+    default_stdin = None
     stderrTempFiles = []
     opened_files = []
     named_temp_files = []
     builtin_commands = set(['cat', 'diff'])
     builtin_commands_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "builtin_commands")
     inproc_builtins = {'cd': executeBuiltinCd,
                        'export': executeBuiltinExport,
                        'echo': executeBuiltinEcho,