Move run_command into test.helpers (#4683)

Split out of #4403, these are helpers, and will eventually be used by other tests.

mypy/test/helpers.py

@@ -1,11 +1,13 @@
 import os
 import re
+import subprocess
 import sys
 import time
 
 from typing import List, Dict, Tuple, Callable, Any, Optional
 
 from mypy import defaults
+from mypy.test.config import test_temp_dir
 
 import pytest  # type: ignore  # no pytest in typeshed
 
@@ -327,3 +329,30 @@ def parse_options(program_text: str, testcase: DataDrivenTestCase,
         options.python_version = testcase_pyversion(testcase.file, testcase.name)
 
     return options
+
+
+def split_lines(*streams: bytes) -> List[str]:
+    """Returns a single list of string lines from the byte streams in args."""
+    return [
+        s
+        for stream in streams
+        for s in stream.decode('utf8').splitlines()
+    ]
+
+
+def run_command(cmdline: List[str], *, env: Optional[Dict[str, str]] = None,
+                timeout: int = 300, cwd: str = test_temp_dir) -> Tuple[int, List[str]]:
+    """A poor man's subprocess.run() for 3.4 compatibility."""
+    process = subprocess.Popen(
+        cmdline,
+        env=env,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        cwd=cwd,
+    )
+    try:
+        out, err = process.communicate(timeout=timeout)
+    except subprocess.TimeoutExpired:
+        out = err = b''
+        process.kill()
+    return process.returncode, split_lines(out, err)

mypy/test/testpythoneval.py

@@ -13,15 +13,15 @@
 import os
 import os.path
 import re
-import subprocess
 import sys
 
 import pytest  # type: ignore  # no pytest in typeshed
-from typing import Dict, List, Tuple, Optional
+
+from typing import List
 
 from mypy.test.config import test_temp_dir
 from mypy.test.data import DataDrivenTestCase, DataSuite
-from mypy.test.helpers import assert_string_arrays_equal
+from mypy.test.helpers import assert_string_arrays_equal, run_command
 from mypy.util import try_find_python2_interpreter
 from mypy import api
 
@@ -79,7 +79,7 @@ def test_python_evaluation(testcase: DataDrivenTestCase) -> None:
             output.append(line.rstrip("\r\n"))
     if returncode == 0:
         # Execute the program.
-        returncode, interp_out = run([interpreter, program])
+        returncode, interp_out = run_command([interpreter, program])
         output.extend(interp_out)
     # Remove temp file.
     os.remove(program_path)
@@ -88,35 +88,7 @@ def test_python_evaluation(testcase: DataDrivenTestCase) -> None:
                                    testcase.file, testcase.line))
 
 
-def split_lines(*streams: bytes) -> List[str]:
-    """Returns a single list of string lines from the byte streams in args."""
-    return [
-        s.rstrip('\n\r')
-        for stream in streams
-        for s in str(stream, 'utf8').splitlines()
-    ]
-
-
 def adapt_output(testcase: DataDrivenTestCase) -> List[str]:
     """Translates the generic _program.py into the actual filename."""
     program = '_' + testcase.name + '.py'
     return [program_re.sub(program, line) for line in testcase.output]
-
-
-def run(
-    cmdline: List[str], *, env: Optional[Dict[str, str]] = None, timeout: int = 300
-) -> Tuple[int, List[str]]:
-    """A poor man's subprocess.run() for 3.3 and 3.4 compatibility."""
-    process = subprocess.Popen(
-        cmdline,
-        env=env,
-        stdout=subprocess.PIPE,
-        stderr=subprocess.PIPE,
-        cwd=test_temp_dir,
-    )
-    try:
-        out, err = process.communicate(timeout=timeout)
-    except subprocess.TimeoutExpired:
-        out = err = b''
-        process.kill()
-    return process.returncode, split_lines(out, err)