add support for the --user option to docker run

Username or UID to run commands as inside the container.
https://docs.docker.com/engine/reference/run/#user

Resolves #135

README.rst

@@ -121,6 +121,10 @@ The ``[docker:container-name]`` section may contain the following directives:
     test run until the container reports healthy, and will fail the test
     run if it never does so (within the parameters specified).
 
+``user``
+    The `user<https://docs.docker.com/engine/reference/run/#user>`__ Username
+    or UID to run commands as inside the container.
+
 Command-Line Arguments
 ----------------------
 
@@ -182,6 +186,8 @@ Example
     # testing use cases, as this could persist data between test runs
     volumes =
         bind:rw:/my/own/datadir:/var/lib/postgresql/data
+    # The uid (or username) to run commands as inside the container.
+    user = 1234
 
     [docker:appserv]
     # You can use any value that `docker run` would accept as the image

tox_docker/config.py

@@ -19,6 +19,8 @@
     r"$"
 )
 
+# uid or username. valid username regex from useradd(8)
+USER = re.compile(r"[a-z_][a-z0-9_-]*[$]?|[0-9]+")
 
 def runas_name(container_name: str, pid: Optional[int] = None) -> str:
     """
@@ -103,6 +105,19 @@ def __init__(self, config_line: str) -> None:
         )
 
 
+class User:
+    def __init__(self, config_line: str) -> None:
+        match = USER.match(config_line)
+        if not match:
+            raise ValueError(f"{config_line!r} is not a valid user name")
+        self.username = config_line
+        self.uid = None
+        try:
+            self.uid = int(self.username)
+        except ValueError:
+            pass
+
+
 class ContainerConfig:
     def __init__(
         self,
@@ -118,6 +133,7 @@ def __init__(
         ports: Optional[Collection[Port]] = None,
         links: Optional[Collection[Link]] = None,
         volumes: Optional[Collection[Volume]] = None,
+        user: Optional[User] = None,
     ) -> None:
         self.name = name
         self.runas_name = runas_name(name)
@@ -139,3 +155,4 @@ def __init__(
             int(healthcheck_start_period) if healthcheck_start_period else None
         )
         self.healthcheck_retries = healthcheck_retries
+        self.user = user

tox_docker/plugin.py

@@ -97,6 +97,10 @@ def docker_run(
         if not os.path.exists(source):
             raise ValueError(f"Volume source {source!r} does not exist")
 
+    user = None
+    if container_config.user:
+        user = container_config.user.uid or container_config.user.username
+
     log(f"run {container_config.image!r} (from {container_config.name!r})")
     container = docker.containers.run(
         str(container_config.image),
@@ -108,6 +112,7 @@ def docker_run(
         ports=ports,
         publish_all_ports=len(ports) == 0,
         mounts=container_config.mounts,
+        user=user,
     )
     container.reload()  # TODO: why do we need this?
     return container

tox_docker/tox3/config.py

@@ -12,6 +12,7 @@
     Port,
     RunningContainers,
     Volume,
+    User,
 )
 
 # nanoseconds in a second; named "SECOND" so that "1.5 * SECOND" makes sense
@@ -133,6 +134,10 @@ def parse_container_config(
     if reader.getstring("volumes"):
         volumes = [Volume(line) for line in reader.getlist("volumes")]
 
+    user = None
+    if reader.getstring("user"):
+        user = User(reader.getstring("user"))
+
     return ContainerConfig(
         name=container_name,
         image=Image(reader.getstring("image")),
@@ -146,4 +151,5 @@ def parse_container_config(
         ports=ports,
         links=links,
         volumes=volumes,
+        user=user
     )

tox_docker/tox4/config.py

@@ -2,7 +2,7 @@
 
 from tox.config.sets import ConfigSet
 
-from tox_docker.config import ContainerConfig, Image, Link, Port, Volume
+from tox_docker.config import ContainerConfig, Image, Link, Port, Volume, User
 
 # nanoseconds in a second; named "SECOND" so that "1.5 * SECOND" makes sense
 SECOND = 1000000000
@@ -86,6 +86,12 @@ def register_config(self) -> None:
             default=0,
             desc="docker healthcheck retry count",
         )
+        self.add_config(
+            keys=["user"],
+            of_type=User,
+            default=None,
+            desc="Username or UID to run commands as inside the container",
+        )
 
 
 def parse_container_config(docker_config: DockerConfigSet) -> ContainerConfig:
@@ -102,4 +108,5 @@ def parse_container_config(docker_config: DockerConfigSet) -> ContainerConfig:
         ports=docker_config["ports"],
         links=docker_config["links"],
         volumes=docker_config["volumes"],
+        user=docker_config["user"]
     )