Support pip's --user option in mypy's --install-types

docs/source/command_line.rst

@@ -1083,6 +1083,13 @@ Miscellaneous
    stub packages were found, they are installed and then another run
    is performed.
 
+.. option:: --user
+
+   When used together with :option:`--install-types <mypy
+   --install-types>`, this causes mypy to install all suggested stub
+   packages using pip and installing them to the user's local python
+   package install location by passing `--user` to `pip` command.
+
 .. option:: --junit-xml JUNIT_XML
 
     Causes mypy to generate a JUnit XML test result document with

mypy/main.py

@@ -81,6 +81,9 @@ def main(
     if options.non_interactive and not options.install_types:
         fail("error: --non-interactive is only supported with --install-types", stderr, options)
 
+    if options.user and not options.install_types:
+        fail("error: --user is only supported with --install-types", stderr, options)
+
     if options.install_types and not options.incremental:
         fail(
             "error: --install-types not supported with incremental mode disabled", stderr, options
@@ -1094,6 +1097,14 @@ def add_invertible_flag(
         group=other_group,
         inverse="--interactive",
     )
+    other_group.add_argument(
+        "--user",
+        action="store_true",
+        help=(
+            "Install stubs to the user's local python package install "
+            + "location when used together with --install-types"
+        ),
+    )
 
     if server_options:
         # TODO: This flag is superfluous; remove after a short transition (2018-03-16)
@@ -1561,7 +1572,8 @@ def install_types(
         print()
     print("Installing missing stub packages:")
     assert options.python_executable, "Python executable required to install types"
-    cmd = [options.python_executable, "-m", "pip", "install"] + packages
+    pip_options = ["--user"] if options.user else []
+    cmd = [options.python_executable, "-m", "pip", "install"] + pip_options + packages
     print(formatter.style(" ".join(cmd), "none", bold=True))
     print()
     if not non_interactive:

mypy/options.py

@@ -358,6 +358,8 @@ def __init__(self) -> None:
         # Install missing stub packages in non-interactive mode (don't prompt for
         # confirmation, and don't show any errors)
         self.non_interactive = False
+        # Install missing stub packages into user's local package installation directory
+        self.user = False
         # When we encounter errors that may cause many additional errors,
         # skip most errors after this many messages have been reported.
         # -1 means unlimited.

test-data/unit/cmdline.test

@@ -1348,6 +1348,25 @@ pkg.py:1: error: "int" not callable
 error: --install-types not supported without python executable or site packages
 == Return code: 2
 
+[case testCmdlineUserOptionWithoutInstallTypes]
+# cmd: mypy --user -m pkg
+[out]
+error: --user is only supported with --install-types
+== Return code: 2
+
+[case testCmdlineUserOptionInstallTypesNothingToDo]
+# cmd: mypy --install-types --user -m pkg
+[file pkg.py]
+1()
+[out]
+pkg.py:1: error: "int" not callable
+
+[case testCmdlineUserOptionInstallTypesNothingToDoNoError]
+# cmd: mypy --install-types --user -m pkg
+[file pkg.py]
+1 + 2
+[out]
+
 [case testCmdlineInteractiveInstallTypesNothingToDo]
 # cmd: mypy --install-types -m pkg
 [file pkg.py]