Add support for tmpfs mounts.

.gitignore

@@ -6,3 +6,4 @@ version.txt
 tox_docker.egg-info
 build/
 dist/
+.idea

README.rst

@@ -109,11 +109,12 @@ The ``[docker:container-name]`` section may contain the following directives:
 ``volumes``
     A multi-line list of `volumes
     <https://docs.docker.com/storage/volumes/>`__ to make available to the
-    container, as ``<type>:<options>:<outside_path_or_name>:<inside_path>``.
-    The ``type`` must be ``bind``, and the only supported options are ``rw``
-    (read-write) or ``ro`` (read-only). The ``outside_path_or_name`` must
-    be a path that exists on the host system. Both the ``outside_path``
-    and ``inside_path`` must be absolute paths.
+    container, as ``<type>:<options>:[<outside_path_or_name>:]<inside_path>``.
+    The ``type`` must be ``bind`` or ``tmpfs``. For ``bind`` type the only supported options are ``rw``
+    (read-write) or ``ro`` (read-only). The ``tmpfs`` type additionally supports ``size`` and ``mode`` options with ``;`` as delimiter.
+    The ``outside_path`` is required for the ``bind`` type and must be a path that exists on the host system.
+    For the ``tmpfs`` type ``outside_path`` should NOT be specified.
+    Both the ``outside_path`` and ``inside_path`` must be absolute paths.
 
 ``healthcheck_cmd``, ``healthcheck_interval``, ``healthcheck_retries``, ``healthcheck_start_period``, ``healthcheck_timeout``
     These set or customize parameters of the container `health check
@@ -183,12 +184,14 @@ Example
     healthcheck_retries = 30
     healthcheck_interval = 1
     healthcheck_start_period = 1
-    # Configure a bind-mounted volume on the host to store Postgres' data
+    # Configure a bind-mounted volume on the host to store Postgres' data and tmpfs as /tmp/
     # NOTE: this is included for demonstration purposes of tox-docker's
-    # volume capability; you probably _don't_ want to do this for real
+    # volume capability; you probably _don't_ want to use bind mounts for real
     # testing use cases, as this could persist data between test runs
     volumes =
         bind:rw:/my/own/datadir:/var/lib/postgresql/data
+        tmpfs:rw;size=64m;mode=1777:/tmp/
+
 
     [docker:appserv]
     # You can use any value that `docker run` would accept as the image

tox.ini

@@ -70,6 +70,7 @@ healthcheck_timeout = 1
 healthcheck_start_period = 1
 volumes =
     bind:rw:{toxworkdir}:/healthcheck/web
+    tmpfs:rw;size=1m;mode=1777:/tmp/
 
 # do NOT add this env to the envlist; it is supposed to fail,
 # and the CI scripts run it directly with this expectation

tox_docker/config.py

@@ -1,5 +1,5 @@
 from pathlib import Path
-from typing import Collection, Dict, List, Mapping, Optional
+from typing import Collection, Dict, List, Mapping, Optional, Union
 import os
 import os.path
 import re
@@ -118,25 +118,69 @@ def __init__(self, config_line: str) -> None:
 class Volume:
     def __init__(self, config_line: str) -> None:
         parts = config_line.split(":")
-        if len(parts) != 4:
+        if len(parts) < 3 or len(parts) > 4:
             raise ValueError(f"Volume {config_line!r} is malformed")
-        if parts[0] != "bind":
-            raise ValueError(f"Volume {config_line!r} type must be 'bind:'")
-        if parts[1] not in ("ro", "rw"):
-            raise ValueError(f"Volume {config_line!r} options must be 'ro' or 'rw'")
-
-        volume_type, mode, outside, inside = parts
-        if not os.path.isabs(outside):
-            raise ValueError(f"Volume source {outside!r} must be an absolute path")
-        if not os.path.isabs(inside):
-            raise ValueError(f"Mount point {inside!r} must be an absolute path")
-
-        self.docker_mount = Mount(
-            source=outside,
-            target=inside,
-            type=volume_type,
-            read_only=bool(mode == "ro"),
-        )
+
+        volume_type, options_str, *_outside_path, inside_path = parts
+
+        if not os.path.isabs(inside_path):
+            raise ValueError(f"Mount point {inside_path!r} must be an absolute path")
+
+        mount_params = {
+            "target": inside_path,
+            "type": volume_type,
+            **self._parse_options(config_line, volume_type, options_str),
+        }
+
+        # bind-specific checks and setup
+        if volume_type == "bind":
+            if len(_outside_path) != 1:
+                raise ValueError(
+                    f"Volume {config_line!r} of type 'bind' must have an outside path"
+                )
+            outside = _outside_path[0]
+
+            if not os.path.isabs(outside):
+                raise ValueError(f"Volume source {outside!r} must be an absolute path")
+            mount_params["source"] = outside
+        # tmpfs-specific setup
+        elif volume_type == "tmpfs":
+            # tmpfs does not have source, so emtpy string
+            mount_params["source"] = ""
+        else:
+            raise ValueError(f"Volume {config_line!r} type must be 'bind' or 'tmpfs'")
+
+        self.docker_mount = Mount(**mount_params)
+
+    def _parse_options(
+        self, config_line: str, volume_type: str, options_str: str
+    ) -> dict:
+        """Parse volume options into `Mount()` params."""
+        result: Dict[str, Union[str, int, bool]] = {}
+        (
+            access_mode,
+            *other_options,
+        ) = options_str.split(";")
+
+        # parsing access mode
+        if access_mode not in ("ro", "rw"):
+            raise ValueError(f"Volume {config_line!r} access mode must be 'ro' or 'rw'")
+        result["read_only"] = bool(access_mode == "ro")
+
+        # parsing tmpfs-specific options
+        if volume_type == "tmpfs":
+            for other_option in other_options:
+                key, value = other_option.split("=")
+                if key == "size":  # volume size, such as 64m
+                    result["tmpfs_size"] = value
+                elif key == "mode":  # permissions, such as 1777
+                    result["tmpfs_mode"] = int(value)
+                else:
+                    raise ValueError(
+                        f"'{other_option!r}' is not a valid option for volume of type '{volume_type}'"
+                    )
+
+        return {}
 
 
 class ContainerConfig:

tox_docker/plugin.py

@@ -190,7 +190,7 @@ def docker_run(
 
     for mount in container_config.mounts:
         source = mount["Source"]
-        if not os.path.exists(source):
+        if mount["Type"] != "tmpfs" and not os.path.exists(source):
             raise ValueError(f"Volume source {source!r} does not exist")
 
     assert container_config.runnable_image