[Lit] Add pushd and popd builtins

[dgoldman]

Summary

This behaves just like the sh/cmd.exe equivalents.

[compnerd]

This seems reasonable to me. I think that a bit more exposition in the commit message is warranted though: explain why/how they are useful (i.e. they can be useful to validating the driver behaviour for path handling).

[dgoldman]

Update commit message

llvm/utils/lit/lit/TestRunner.py

 # COMMAND that follows %dbg(ARG) is also captured. COMMAND can be
 # empty as a result of conditinal substitution.
 kPdbgRegex = '%dbg\\(([^)\'"]*)\\)(.*)'
 
 class ShellEnvironment(object):
 
     """Mutable shell environment containing things like CWD and env vars.
 
-    Environment variables are not implemented, but cwd tracking is.
+    Environment variables are not implemented, but cwd tracking is. In addition,
+    we maintain a dir stack for pushd/popd.
     """
 
     def __init__(self, cwd, env):
         self.cwd = cwd
         self.env = dict(env)
+        self.dirStack = []
+
+    def change_dir(self, newdir):
+        if os.path.isabs(newdir):
+            self.cwd = newdir
+        else:
+            self.cwd = os.path.realpath(os.path.join(self.cwd, newdir))
 
 class TimeoutHelper(object):
     """
         Object used to helper manage enforcing a timeout in
         _executeShCmd(). It is passed through recursive calls
         to collect processes that have been executed so that when
         the timeout happens they can be killed.
     """
for arg_idx, arg in enumerate(args[1:]):
             arg_idx_next = arg_idx + 1
             break
         env.env[key] = val
     return args[arg_idx_next:]
 
 def executeBuiltinCd(cmd, shenv):
     """executeBuiltinCd - Change the current directory."""
     if len(cmd.args) != 2:
-        raise InternalShellError("'cd' supports only one argument")
-    newdir = cmd.args[1]
+        raise InternalShellError(cmd, "'cd' supports only one argument")
     # Update the cwd in the parent environment.
-    if os.path.isabs(newdir):
-        shenv.cwd = newdir
-    else:
-        shenv.cwd = os.path.realpath(os.path.join(shenv.cwd, newdir))
+    shenv.change_dir(cmd.args[1])
     # The cd builtin always succeeds. If the directory does not exist, the
     # following Popen calls will fail instead.
     return ShellCommandResult(cmd, "", "", 0, False)
 
+def executeBuiltinPushd(cmd, shenv):
+    """executeBuiltinPushd - Change the current dir and save the old."""
+    if len(cmd.args) != 2:
+        raise InternalShellError(cmd, "'pushd' supports only one argument")
+    shenv.dirStack.append(shenv.cwd)
+    shenv.change_dir(cmd.args[1])
+    return ShellCommandResult(cmd, "", "", 0, False)
+
+def executeBuiltinPopd(cmd, shenv):
+    """executeBuiltinPopd - Restore a previously saved working directory."""
+    if len(cmd.args) != 1:
+        raise InternalShellError(cmd, "'popd' does not support arguments")
+    if not shenv.dirStack:
+        raise InternalShellError(cmd, "popd: directory stack empty")
+    shenv.cwd = shenv.dirStack.pop()
+    return ShellCommandResult(cmd, "", "", 0, False)
+
 def executeBuiltinExport(cmd, shenv):
     """executeBuiltinExport - Set an environment variable."""
     if len(cmd.args) != 2:
         raise InternalShellError("'export' supports only one argument")
     updateEnv(shenv, cmd.args)
     return ShellCommandResult(cmd, "", "", 0, False)
 
 def executeBuiltinEcho(cmd, shenv):
def _executeShCmd(cmd, shenv, results, timeoutHelper):
     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,
                        'mkdir': executeBuiltinMkdir,
+                       'popd': executeBuiltinPopd,
+                       'pushd': executeBuiltinPushd,
                        'rm': executeBuiltinRm,
                        ':': executeBuiltinColon}
     # To avoid deadlock, we use a single stderr stream for piped
     # output. This is null until we have seen some output using
     # stderr.
     for i,j in enumerate(cmd.commands):
         # Reference the global environment by default.
         cmd_shenv = shenv

llvm/utils/lit/tests/Inputs/shtest-pushd-popd/lit.cfg

+import lit.formats
+config.name = 'shtest-pushd-popd'
+config.suffixes = ['.txt']
+config.test_format = lit.formats.ShTest(execute_external=False)

llvm/utils/lit/tests/Inputs/shtest-pushd-popd/popd-args.txt

+# RUN: popd invalid
 No newline at end of file

llvm/utils/lit/tests/Inputs/shtest-pushd-popd/popd-no-stack.txt

+# RUN: popd
 No newline at end of file

llvm/utils/lit/tests/Inputs/shtest-pushd-popd/pushd-popd-ok.txt

+# RUN: rm -rf %t/UserFoo && mkdir -p %t/UserFoo/FooDocs
+# RUN: touch %t/UserFoo/user.txt %t/UserFoo/FooDocs/doc.txt
+# RUN: pushd %t/UserFoo
+# RUN: pushd FooDocs
+# RUN: cat doc.txt
+# RUN: popd
+# RUN: cat user.txt
+# RUN: popd
 No newline at end of file

llvm/utils/lit/tests/Inputs/shtest-pushd-popd/pushd-too-many-args.txt

+# RUN: pushd a b
 No newline at end of file

llvm/utils/lit/tests/shtest-pushd-popd.py

+# Check the pushd and popd commands
+
+# RUN: not %{lit} -a -v %{inputs}/shtest-pushd-popd \
+# RUN: | FileCheck -match-full-lines %s
+#
+# END.
+
+# CHECK: -- Testing: 4 tests{{.*}}
+
+# CHECK: FAIL: shtest-pushd-popd :: popd-args.txt ({{[^)]*}})
+# CHECK: $ "popd" "invalid"
+# CHECK: 'popd' does not support arguments
+
+# CHECK: FAIL: shtest-pushd-popd :: popd-no-stack.txt ({{[^)]*}})
+# CHECK: $ "popd"
+# CHECK: popd: directory stack empty
+
+# CHECK: FAIL: shtest-pushd-popd :: pushd-too-many-args.txt ({{[^)]*}})
+# CHECK: $ "pushd" "a" "b"
+# CHECK: 'pushd' supports only one argument
+
+# CHECK: Passed:  1
+# CHECK: Failed:  3
+# CHECK-NOT: {{.}}