tests(Theme): Add tests and fix a few things

Author: gadenbuie

shiny/ui/_theme.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import copy
 import os
 import tempfile
 from textwrap import dedent
@@ -101,11 +102,21 @@ def preset(self, value: ShinyThemePreset) -> None:
         check_is_valid_preset(value)
         self._preset = value
 
-        if self._css != "precompiled":
+        has_customizations = (
+            len(self._functions) > 0
+            or len(self._defaults) > 0
+            or len(self._mixins) > 0
+            or len(self._rules) > 0
+        )
+
+        if has_customizations:
             self._css = ""
+        else:
+            self._css = "precompiled" if value in ShinyThemePresetsBundled else ""
+
         self._css_temp_srcdir = None
 
-    def add_functions(self: T, *args: list[str]) -> T:
+    def add_functions(self: T, *args: str) -> T:
         """
         Add custom Sass functions to the theme.
 
@@ -119,10 +130,12 @@ def add_functions(self: T, *args: list[str]) -> T:
             The Sass functions to add as a single or multiple strings.
         """
         self._css = ""
-        self._functions.extend(dedent_array(*args))
+        self._functions.extend(dedent_array(args))
         return self
 
-    def add_defaults(self: T, *args: str, **kwargs: dict[str, str]) -> T:
+    def add_defaults(
+        self: T, *args: str, **kwargs: str | float | int | bool | None
+    ) -> T:
         """
         Add custom default values to the theme.
 
@@ -142,7 +155,11 @@ def add_defaults(self: T, *args: str, **kwargs: dict[str, str]) -> T:
             `.add_defaults("$primary-color: #ff0000;")`.
         """
         if len(args) > 0 and len(kwargs) > 0:
+            # Python forces positional arguments to come _before_ kwargs, but default
+            # argument order might matter. To be safe, we force users to pick one order.
             raise ValueError("Cannot provide both positional and keyword arguments")
+        elif len(args) == 0 and len(kwargs) == 0:
+            return self
 
         defaults: list[str] = list(args)
 
@@ -151,6 +168,8 @@ def add_defaults(self: T, *args: str, **kwargs: dict[str, str]) -> T:
                 key.replace("_", "-")
                 if isinstance(value, bool):
                     value = "true" if value else "false"
+                elif value is None:
+                    value = "null"
                 defaults.append(f"${key}: {value};")
 
         # Add args to the front of _defaults
@@ -232,14 +251,14 @@ def to_css(self) -> str:
         if self._css:
             if self._css == "precompiled":
                 return self._read_precompiled_css()
-            return self._css
+            return copy.copy(self._css)
 
         check_libsass_installed()
         import sass
 
         self._css = sass.compile(string=self.to_sass())
 
-        return self._css
+        return copy.copy(self._css)
 
     def _read_precompiled_css(self) -> str:
         path = path_pkg_preset(self._preset, "preset.min.css")

tests/pytest/test_theme.py

@@ -0,0 +1,115 @@
+import pytest
+
+from shiny.ui import Theme
+from shiny.ui._theme import (
+    ShinyThemePreset,
+    ShinyThemePresets,
+    ShinyThemePresetsBundled,
+)
+
+
+def test_theme_stores_values_correctly():
+    theme = (
+        Theme("shiny")
+        .add_defaults(
+            headings_color="red",
+            bar_color="purple",
+            select_color_text="green",
+            bslib_dashboard_design=True,
+        )
+        .add_functions("@function get-color($color) { @return $color; }")
+        .add_rules(
+            """
+            strong { color: $primary; }
+            .sidebar-title { color: $danger; }
+            """,
+            ".special { color: $warning; }",
+        )
+        .add_mixins("@mixin alert { color: $alert; }")
+    )
+
+    check_vars = [
+        "_preset",
+        "name",
+        "_functions",
+        "_defaults",
+        "_mixins",
+        "_rules",
+        "_css",
+    ]
+
+    theme_dict = {k: v for k, v in vars(theme).items() if k in check_vars}
+
+    assert theme_dict == {
+        "_preset": "shiny",
+        "name": None,
+        "_functions": ["@function get-color($color) { @return $color; }"],
+        "_defaults": [
+            "$headings_color: red;",
+            "$bar_color: purple;",
+            "$select_color_text: green;",
+            "$bslib_dashboard_design: true;",
+        ],
+        "_mixins": ["@mixin alert { color: $alert; }"],
+        "_rules": [
+            "\nstrong { color: $primary; }\n.sidebar-title { color: $danger; }\n",
+            ".special { color: $warning; }",
+        ],
+        "_css": "",
+    }
+
+
+def test_theme_preset_must_be_valid():
+    with pytest.raises(ValueError, match="Invalid preset"):
+        Theme("not_a_valid_preset")  # type: ignore
+
+
+@pytest.mark.parametrize("preset", ShinyThemePresets)
+def test_theme_css_compiles_and_is_cached(preset: ShinyThemePreset):
+    theme = Theme(preset)
+    if preset in ShinyThemePresetsBundled:
+        assert theme._css == "precompiled"
+    else:
+        assert theme._css == ""
+
+    # Adding rules resets the theme's cached CSS
+    theme.add_rules(".MY_RULE { color: red; }")
+    assert theme._css == ""
+
+    first_css = theme.to_css()
+    assert first_css.find("Bootstrap") != -1
+    assert first_css.find(".MY_RULE") != -1
+    assert theme.to_css() == first_css  # Cached value is returned
+
+    # Adding another customization resets the theme's cached CSS
+    theme.add_mixins(".MY_MIXIN { color: blue; }")
+    second_css = theme.to_css()
+    assert second_css != first_css, "First and second compiled CSS are the same"
+    assert second_css.find("Bootstrap") != -1
+    assert second_css.find(".MY_MIXIN") != -1
+
+
+def test_theme_update_preset():
+    theme = Theme("shiny")
+    assert theme._preset == "shiny"
+    assert theme._css == "precompiled" if "shiny" in ShinyThemePresetsBundled else ""
+
+    theme.preset = "bootstrap"
+    assert theme._preset == "bootstrap"
+    assert theme._css == (
+        "precompiled" if "bootstrap" in ShinyThemePresetsBundled else ""
+    )
+
+    theme.preset = "sketchy"
+    assert theme._preset == "sketchy"
+    assert theme._css == (
+        "precompiled" if "sketchy" in ShinyThemePresetsBundled else ""
+    )
+
+    with pytest.raises(ValueError, match="Invalid preset"):
+        theme.preset = "not_a_valid_preset"  # type: ignore
+
+
+def test_theme_defaults_positional_or_keyword():
+    with pytest.raises(ValueError, match="Cannot provide both"):
+        Theme("shiny").add_defaults("$color: red;", other_color="green")