[lit] Add support for readfile to external shell

This patch adds support for the new lit %{readfile:<filename>}
substitution to the external shell. The implementation currently just
appends some test commands to ensure the file exists and uses a subshell
with cat. This is intended to enable running tests using the
substitution in the external shell before we fully switch over to the
internal shell.

This code is designed to be temporary with us deleting it once
everything has migrated over to the internal shell and we are able to
remove the external shell code paths.

Reviewers: petrhosek, cmtice, pogo59, ilovepi, arichardson

Reviewed By: cmtice

Pull Request: llvm/llvm-project#159431

Author: boomanaiden154

llvm/utils/lit/lit/TestRunner.py

@@ -2417,6 +2417,22 @@ def runOnce(
     )
 
 
+def _expandLateSubstitutionsExternal(commandLine):
+    filePaths = []
+
+    def _replaceReadFile(match):
+        filePath = match.group(1)
+        filePaths.append(filePath)
+        return "$(cat %s)" % shlex.quote(filePath)
+
+    commandLine = re.sub(r"%{readfile:([^}]*)}", _replaceReadFile, commandLine)
+    # Add test commands before the command to check if the file exists as
+    # cat inside a subshell will never return a non-zero exit code outside
+    # of the subshell.
+    for filePath in filePaths:
+        commandLine = "%s && test -e %s" % (commandLine, filePath)
+    return commandLine
+
 def executeShTest(
     test, litConfig, useExternalSh, extra_substitutions=[], preamble_commands=[]
 ):
@@ -2447,4 +2463,8 @@ def executeShTest(
         recursion_limit=test.config.recursiveExpansionLimit,
     )
 
+    if useExternalSh:
+        for index, command in enumerate(script):
+            script[index] = _expandLateSubstitutionsExternal(command)
+
     return _runShTest(test, litConfig, useExternalSh, script, tmpBase)

llvm/utils/lit/tests/Inputs/shtest-readfile/lit.cfg

@@ -1,7 +1,19 @@
+import os
+
 import lit.formats
+import lit.util
 
 config.name = "shtest-readfile"
 config.suffixes = [".txt"]
-config.test_format = lit.formats.ShTest(execute_external=False)
+lit_shell_env = os.environ.get("LIT_USE_INTERNAL_SHELL")
+use_lit_shell = lit.util.pythonize_bool(lit_shell_env)
+config.test_format = lit.formats.ShTest(execute_external=not use_lit_shell)
 config.test_source_root = None
 config.test_exec_root = None
+
+# If we are testing with the external shell, remove the fake-externals from
+# PATH so that we use mkdir in the tests.
+if not use_lit_shell:
+    path_parts = config.environment["PATH"].split(os.path.pathsep)
+    path_parts = [path_part for path_part in path_parts if "fake-externals" not in path_part]
+    config.environment["PATH"] = os.path.pathsep.join(path_parts)

llvm/utils/lit/tests/shtest-readfile-external.py

@@ -0,0 +1,22 @@
+## Tests the readfile substitution.
+
+# UNSUPPORTED: system-windows
+# RUN: env LIT_USE_INTERNAL_SHELL=0 not %{lit} -a -v %{inputs}/shtest-readfile | FileCheck -match-full-lines -DTEMP_PATH=%S/Inputs/shtest-readfile/Output %s
+
+# CHECK: -- Testing: 4 tests{{.*}}
+
+# CHECK-LABEL: FAIL: shtest-readfile :: absolute-paths.txt ({{[^)]*}})
+# CHECK: echo $(cat [[TEMP_PATH]]/absolute-paths.txt.tmp) && test -e [[TEMP_PATH]]/absolute-paths.txt.tmp {{.*}}
+# CHECK: + echo hello
+
+# CHECK-LABEL: FAIL: shtest-readfile :: file-does-not-exist.txt ({{[^)]*}})
+# CHECK: echo $(cat /file/does/not/exist) && test -e /file/does/not/exist {{.*}}
+# CHECK: cat: /file/does/not/exist: No such file or directory
+
+# CHECK-LABEL: FAIL: shtest-readfile :: relative-paths.txt ({{[^)]*}})
+# CHECK: echo $(cat rel_path_test_folder/test_file) && test -e rel_path_test_folder/test_file {{.*}}
+# CHECK: + echo hello
+
+# CHECK-LABEL: FAIL: shtest-readfile :: two-same-line.txt ({{[^)]*}})
+# CHECK: echo $(cat [[TEMP_PATH]]/two-same-line.txt.tmp.1) $(cat [[TEMP_PATH]]/two-same-line.txt.tmp.2) && test -e [[TEMP_PATH]]/two-same-line.txt.tmp.1 && test -e [[TEMP_PATH]]/two-same-line.txt.tmp.2 {{.*}}
+# CHECK: + echo hello bye

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

@@ -1,6 +1,6 @@
 ## Tests the readfile substitution.
 
-# RUN: not %{lit} -a -v %{inputs}/shtest-readfile | FileCheck -match-full-lines -DTEMP_PATH=%S%{fs-sep}Inputs%{fs-sep}shtest-readfile%{fs-sep}Output %s
+# RUN: env LIT_USE_INTERNAL_SHELL=1  not %{lit} -a -v %{inputs}/shtest-readfile | FileCheck -match-full-lines -DTEMP_PATH=%S%{fs-sep}Inputs%{fs-sep}shtest-readfile%{fs-sep}Output %s
 
 # CHECK: -- Testing: 4 tests{{.*}}