fix(core): configValidation should allow inline theme functions (#6496)

packages/docusaurus/src/server/__tests__/__snapshots__/configValidation.test.ts.snap

@@ -108,7 +108,76 @@ exports[`normalizeConfig should throw error if scripts doesn't have src 1`] = `
 "
 `;
 
+exports[`normalizeConfig should throw error if themes is not a string and it's not an array #1 for the input of: [123] 1`] = `
+" => Bad Docusaurus theme value as path [themes,0].
+Example valid theme config:
+{
+  themes: [
+    [\\"@docusaurus/theme-classic\\",options],
+    \\"./myTheme\\",
+    [\\"./myTheme\\",{someOption: 42}],
+    function myTheme() { },
+    [function myTheme() { },options]
+  ],
+};
+
+"
+`;
+
+exports[`normalizeConfig should throw error if themes is not an array of [string, object][] #1 for the input of: [[Array]] 1`] = `
+" => Bad Docusaurus theme value as path [themes,0].
+Example valid theme config:
+{
+  themes: [
+    [\\"@docusaurus/theme-classic\\",options],
+    \\"./myTheme\\",
+    [\\"./myTheme\\",{someOption: 42}],
+    function myTheme() { },
+    [function myTheme() { },options]
+  ],
+};
+
+"
+`;
+
+exports[`normalizeConfig should throw error if themes is not an array of [string, object][] #2 for the input of: [[Array]] 1`] = `
+" => Bad Docusaurus theme value as path [themes,0].
+Example valid theme config:
+{
+  themes: [
+    [\\"@docusaurus/theme-classic\\",options],
+    \\"./myTheme\\",
+    [\\"./myTheme\\",{someOption: 42}],
+    function myTheme() { },
+    [function myTheme() { },options]
+  ],
+};
+
+"
+`;
+
+exports[`normalizeConfig should throw error if themes is not an array of [string, object][] #3 for the input of: [[Array]] 1`] = `
+" => Bad Docusaurus theme value as path [themes,0].
+Example valid theme config:
+{
+  themes: [
+    [\\"@docusaurus/theme-classic\\",options],
+    \\"./myTheme\\",
+    [\\"./myTheme\\",{someOption: 42}],
+    function myTheme() { },
+    [function myTheme() { },options]
+  ],
+};
+
+"
+`;
+
 exports[`normalizeConfig should throw error if themes is not array 1`] = `
 "\\"themes\\" must be an array
 "
 `;
+
+exports[`normalizeConfig should throw error if themes is not array for the input of: {} 1`] = `
+"\\"themes\\" must be an array
+"
+`;

packages/docusaurus/src/server/__tests__/configValidation.test.ts

@@ -117,6 +117,32 @@ describe('normalizeConfig', () => {
     }).toThrowErrorMatchingSnapshot();
   });
 
+  test.each([
+    ['should throw error if themes is not array', {}],
+    [
+      "should throw error if themes is not a string and it's not an array #1",
+      [123],
+    ],
+    [
+      'should throw error if themes is not an array of [string, object][] #1',
+      [['example/path', 'wrong parameter here']],
+    ],
+    [
+      'should throw error if themes is not an array of [string, object][] #2',
+      [[{}, 'example/path']],
+    ],
+    [
+      'should throw error if themes is not an array of [string, object][] #3',
+      [[{}, {}]],
+    ],
+  ])(`%s for the input of: %p`, (_message, themes) => {
+    expect(() => {
+      normalizeConfig({
+        themes,
+      });
+    }).toThrowErrorMatchingSnapshot();
+  });
+
   test.each([
     ['should accept [string] for plugins', ['plain/string']],
     [
@@ -155,6 +181,44 @@ describe('normalizeConfig', () => {
     }).not.toThrowError();
   });
 
+  test.each([
+    ['should accept [string] for themes', ['plain/string']],
+    [
+      'should accept string[] for themes',
+      ['plain/string', 'another/plain/string/path'],
+    ],
+    [
+      'should accept [string, object] for themes',
+      [['plain/string', {it: 'should work'}]],
+    ],
+    [
+      'should accept [string, object][] for themes',
+      [
+        ['plain/string', {it: 'should work'}],
+        ['this/should/work', {too: 'yes'}],
+      ],
+    ],
+    [
+      'should accept ([string, object]|string)[] for themes',
+      [
+        'plain/string',
+        ['plain', {it: 'should work'}],
+        ['this/should/work', {too: 'yes'}],
+      ],
+    ],
+    ['should accept function for theme', [function (_context, _options) {}]],
+    [
+      'should accept [function, object] for theme',
+      [[function (_context, _options) {}, {it: 'should work'}]],
+    ],
+  ])(`%s for the input of: %p`, (_message, themes) => {
+    expect(() => {
+      normalizeConfig({
+        themes,
+      });
+    }).not.toThrowError();
+  });
+
   test('should throw error if themes is not array', () => {
     expect(() => {
       normalizeConfig({

packages/docusaurus/src/server/configValidation.ts

@@ -55,21 +55,33 @@ export const DEFAULT_CONFIG: Pick<
   staticDirectories: [STATIC_DIR_NAME],
 };
 
-const PluginSchema = Joi.alternatives()
+function createPluginSchema(theme: boolean = false) {
-  .try(
+  return (
-    Joi.function(),
+    Joi.alternatives()
-    Joi.array().ordered(Joi.function().required(), Joi.object().required()),
+      .try(
-    Joi.string(),
+        Joi.function(),
-    Joi.array()
+        Joi.array().ordered(Joi.function().required(), Joi.object().required()),
-      .ordered(Joi.string().required(), Joi.object().required())
+        Joi.string(),
-      .length(2),
+        Joi.array()
-    Joi.bool().equal(false), // In case of conditional adding of plugins.
+          .ordered(Joi.string().required(), Joi.object().required())
-  )
+          .length(2),
-  // @ts-expect-error: bad lib def, doesn't recognize an array of reports
+        Joi.bool().equal(false), // In case of conditional adding of plugins.
-  .error((errors) => {
+      )
-    errors.forEach((error) => {
+      // @ts-expect-error: bad lib def, doesn't recognize an array of reports
-      error.message = ` => Bad Docusaurus plugin value as path [${error.path}].
+      .error((errors) => {
-Example valid plugin config:
+        errors.forEach((error) => {
+          const validConfigExample = theme
+            ? `Example valid theme config:
+{
+  themes: [
+    ["@docusaurus/theme-classic",options],
+    "./myTheme",
+    ["./myTheme",{someOption: 42}],
+    function myTheme() { },
+    [function myTheme() { },options]
+  ],
+};`
+            : `Example valid plugin config:
 {
   plugins: [
     ["@docusaurus/plugin-content-docs",options],
@@ -78,16 +90,22 @@ Example valid plugin config:
     function myPlugin() { },
     [function myPlugin() { },options]
   ],
-};
+};`;
-`;
-    });
-    return errors;
-  });
 
-const ThemeSchema = Joi.alternatives().try(
+          error.message = ` => Bad Docusaurus ${
-  Joi.string(),
+            theme ? 'theme' : 'plugin'
-  Joi.array().items(Joi.string().required(), Joi.object().required()).length(2),
+          } value as path [${error.path}].
-);
+${validConfigExample}
+`;
+        });
+        return errors;
+      })
+  );
+}
+
+const PluginSchema = createPluginSchema(false);
+
+const ThemeSchema = createPluginSchema(true);
 
 const PresetSchema = Joi.alternatives().try(
   Joi.string(),