cleaner way to specify import sources

this gives the server more authority over where resources are located
and makes it easier for downstream applications to configure

Author: rmorshea

src/idom/_option.py

@@ -28,14 +28,19 @@ def mutable(self) -> bool:
         """Whether this option can be modified after being loaded"""
         return self._mutable
 
+    @property
+    def default(self) -> _O:
+        """This option's default value"""
+        return self._default
+
     def get(self) -> _O:
         """Get the current value of this option."""
         return self._value
 
     def set(self, new: _O) -> _O:
         """Set the value of this configuration option
 
-        Raises a ``TypeError`` if this option is immutable.
+        Raises a ``TypeError`` if this option is not :attr:`Option.mutable`.
         """
         if not self._mutable:
             raise TypeError(f"{self} cannot be modified after initial load")

src/idom/client/_private.py

@@ -11,6 +11,15 @@
 APP_DIR = HERE / "app"
 BACKUP_BUILD_DIR = APP_DIR / "build"
 
+# the path relative to the build that contains import sources
+IDOM_CLIENT_IMPORT_SOURCE_URL_INFIX = "/_snowpack/pkg"
+
+
+def web_modules_dir() -> Path:
+    return IDOM_CLIENT_BUILD_DIR.get().joinpath(
+        *IDOM_CLIENT_IMPORT_SOURCE_URL_INFIX[1:].split("/")
+    )
+
 
 if not IDOM_CLIENT_BUILD_DIR.get().exists():  # pragma: no cover
     shutil.copytree(BACKUP_BUILD_DIR, IDOM_CLIENT_BUILD_DIR.get(), symlinks=True)

src/idom/client/manage.py

@@ -5,20 +5,16 @@
 from tempfile import TemporaryDirectory
 from typing import Dict, Iterable, List, Sequence, Set, Union
 
-from idom.config import IDOM_CLIENT_BUILD_DIR, IDOM_CLIENT_WEB_MODULE_BASE_URL
+from idom.config import IDOM_CLIENT_IMPORT_SOURCE_URL
 
 from . import _private
 
 
 logger = getLogger(__name__)
 
 
-def web_modules_dir() -> Path:
-    return IDOM_CLIENT_BUILD_DIR.get() / "_snowpack" / "pkg"
-
-
 def web_module_path(package_name: str, must_exist: bool = False) -> Path:
-    path = web_modules_dir().joinpath(*(package_name + ".js").split("/"))
+    path = _private.web_modules_dir().joinpath(*(package_name + ".js").split("/"))
     if must_exist and not path.exists():
         raise ValueError(
             f"Web module {package_name!r} does not exist at path {str(path)!r}"
@@ -35,7 +31,10 @@ def web_module_exports(package_name: str) -> List[str]:
 
 def web_module_url(package_name: str) -> str:
     web_module_path(package_name, must_exist=True)
-    return IDOM_CLIENT_WEB_MODULE_BASE_URL.get() + f"/{package_name}.js"
+    return (
+        IDOM_CLIENT_IMPORT_SOURCE_URL.get()
+        + f"{_private.IDOM_CLIENT_IMPORT_SOURCE_URL_INFIX}/{package_name}.js"
+    )
 
 
 def web_module_exists(package_name: str) -> bool:
@@ -44,7 +43,7 @@ def web_module_exists(package_name: str) -> bool:
 
 def web_module_names() -> Set[str]:
     names = []
-    web_mod_dir = web_modules_dir()
+    web_mod_dir = _private.web_modules_dir()
     for pth in web_mod_dir.glob("**/*.js"):
         rel_pth = pth.relative_to(web_mod_dir)
         if Path("common") in rel_pth.parents:

src/idom/config.py

@@ -31,9 +31,24 @@
 a set of publically available APIs for working with the client.
 """
 
-IDOM_CLIENT_WEB_MODULE_BASE_URL = _option.Option(
-    "IDOM_CLIENT_WEB_MODULE_BASE_URL",
-    default=".",
+
+IDOM_CLIENT_IMPORT_SOURCE_URL = _option.Option(
+    "IDOM_CLIENT_IMPORT_SOURCE_URL",
+    default="/client",
     validator=lambda x: cast(str, x[:-1] if x.endswith("/") else x),
 )
-"""The base URL where all user-installed web modules reside"""
+"""The URL to importable modules containing Javascript components
+
+Setting this to an empty string will given the client control over the location of
+import sources. Using a relative path (e.g. one starting with ``./``) with locate import
+sources relative to a base URL specified by the client. Lastly, an absolute URL
+specifies exactly where import sources are located and ignores are client configuration.
+
+Examples:
+    Empty String:
+        ``CLIENT_SPECIFIED_BASE_URL/my-module.js``
+    Relative Path:
+        ``CLIENT_SPECIFIED_BASE_URL/RELATIVE_PATH/my-module.js``
+    Absolute URL
+        ``ABSOLUTE_PATH/my-module.js``
+"""

tests/test__option.py

@@ -20,6 +20,7 @@ def test_option_from_os_environ():
 def test_option_from_default():
     opt = Option("A_FAKE_OPTION", "default-value")
     assert opt.get() == "default-value"
+    assert opt.get() is opt.default
 
 
 @mock.patch.dict(os.environ, {"A_FAKE_OPTION": "1"})
@@ -47,7 +48,7 @@ def test_option_reset():
     opt.set("a-new-value")
     assert opt.get() == "a-new-value"
     opt.reset()
-    assert opt.get() == "default-value"
+    assert opt.get() is opt.default
 
 
 def test_option_set_returns_last_value():

tests/test_client/test_manage.py

@@ -33,7 +33,7 @@ def test_web_module_path_must_exist():
 
 def test_web_module_url(victory):
     assert web_module_exists("victory")
-    assert web_module_url("victory") == "./victory.js"
+    assert web_module_url("victory") == "/client/_snowpack/pkg/victory.js"
 
 
 def test_web_module_exports(victory):