[llvm] Add text file support for z/OS back in (PR #209259)

[Sean Perry via llvm-commits]

================
@@ -65,18 +66,32 @@ def run(argv, stdin, stdout, stderr, cwd):
 
     for filename in filenames:
         path = filename
-        contents = None
         if not os.path.isabs(path):
             path = os.path.join(cwd, path)
-        try:
-            with open(path, "rb") as fileToCat:
-                contents = fileToCat.read()
-        except IOError as error:
-            error.filename = filename
-            stderr.write(str(error).encode())
-            return 1
+
+        contents = None
+        is_text = False
+        if platform.system() == "OS/390":
+            try:
+                with open(path, "r") as fileToCat:
+                    contents = fileToCat.read()
+                    is_text = True
+            except:
+                pass
+
+        if contents is None:
+            try:
+                with open(path, "rb") as fileToCat:
+                    contents = fileToCat.read()
+            except IOError as error:
+                error.filename = filename
+                stderr.write(str(error).encode())
+                return 1
+
         if show_nonprinting:
             contents = convertToCaretAndMNotation(contents)
+        elif is_text:
+            contents = contents.encode()
----------------
perry-ca wrote:

With the way the code is now the sequence of operations for a text file on z/OS with the --show-nonprinting option is:
1. open the file
2. read the file
3. call the convert function (this calls encode())
4. print the contents

If we called encode() where the is_text flag is set, the sequence would be
1. open the file
2. read the file
3. encode the contents
4. call the convert function (which calls encode() again)
5. print the contents.

I'm thinking of a command like `python cat.py --show-nonprinting text-file`.  I'm pretty sure we came across this when first making this change.

https://github.com/llvm/llvm-project/pull/209259