feat: treat non-seekable files as pipes (#2309)

Previously, attempting to read from a pipe would result in an error:
'not a regular file', disallowing use of files like /dev/stdin or
/dev/fd/3, named fifos, sockets, etc.

The tools already understand how to (try to) read from non-regular
files, so this change attempts to do so when the input is not seek-able
(the "regular file" capability that's in use here).

Additionally, this adds a test for the new behavior using a bash
herestring and process substitution (the latter of which shows up in
argv as something like `/dev/fd/NN`). Since bash isn't commonly
installed on Windows, this change also introduces a new capability to
filter tests to specific platforms (sorry).

3 files changed, 11 insertions, 1 deletions

diff --git a/test/dump/bad-directory.txt b/test/dump/bad-directory.txt
index 253c3b38..4b14cdf9 100644
--- a/test/dump/bad-directory.txt
+++ b/test/dump/bad-directory.txt
@@ -1,5 +1,5 @@
 ;;; RUN: %(wasm-objdump)s -d third_party/
 ;;; ERROR: 1
 (;; STDERR ;;;
-third_party/: not a regular file
+third_party/: is a directory
 ;;; STDERR ;;)
diff --git a/test/pipes.txt b/test/pipes.txt
new file mode 100644
index 00000000..fbe67136
--- /dev/null
+++ b/test/pipes.txt
@@ -0,0 +1,7 @@
+;;; PLATFORMS: Linux Darwin
+;;; RUN: bash -c '%(wasm-stats)s <(%(wat2wasm)s /dev/stdin <<<"(module)" -o /dev/stdout)'
+(;; STDOUT ;;;
+Total opcodes: 0
+Opcode counts:
+Opcode counts with immediates:
+;;; STDOUT ;;)
diff --git a/test/run-tests.py b/test/run-tests.py
index 0bd241ea..370f75ef 100755
--- a/test/run-tests.py
+++ b/test/run-tests.py
@@ -20,6 +20,7 @@ import difflib
 import fnmatch
 import multiprocessing
 import os
+import platform
 import re
 import shlex
 import shutil
@@ -505,6 +506,8 @@ class TestInfo(object):
         elif key == 'ENV':
             # Pattern: FOO=1 BAR=stuff
             self.env = dict(x.split('=') for x in value.split())
+        elif key == 'PLATFORMS':
+            self.skip = platform.system() not in value.split()
         else:
             raise Error('Unknown directive: %s' % key)