Preset: Add common preset overrides mechanism

code/lib/core-server/package.json

@@ -36,6 +36,11 @@
       "node": "./dist/presets/common-preset.js",
       "require": "./dist/presets/common-preset.js"
     },
+    "./dist/presets/common-override-preset": {
+      "types": "./dist/presets/common-override-preset.d.ts",
+      "node": "./dist/presets/common-override-preset.js",
+      "require": "./dist/presets/common-override-preset.js"
+    },
     "./public/favicon.svg": "./public/favicon.svg",
     "./package.json": "./package.json"
   },
@@ -119,7 +124,8 @@
     "entries": [
       "./src/index.ts",
       "./src/presets/babel-cache-preset.ts",
-      "./src/presets/common-preset.ts"
+      "./src/presets/common-preset.ts",
+      "./src/presets/common-override-preset.ts"
     ],
     "platform": "node"
   },

code/lib/core-server/src/build-dev.ts

@@ -80,7 +80,9 @@ export async function buildDevStandalone(
   // We hope to remove this in SB8
   let presets = await loadAllPresets({
     corePresets,
-    overridePresets: [],
+    overridePresets: [
+      require.resolve('@storybook/core-server/dist/presets/common-override-preset'),
+    ],
     ...options,
   });
 
@@ -112,7 +114,10 @@ export async function buildDevStandalone(
       ...corePresets,
       require.resolve('@storybook/core-server/dist/presets/babel-cache-preset'),
     ],
-    overridePresets: previewBuilder.overridePresets ?? [],
+    overridePresets: [
+      ...(previewBuilder.overridePresets || []),
+      require.resolve('@storybook/core-server/dist/presets/common-override-preset'),
+    ],
     ...options,
   });
 

code/lib/core-server/src/build-static.ts

@@ -85,7 +85,9 @@ export async function buildStaticStandalone(options: BuildStaticStandaloneOption
       require.resolve('@storybook/core-server/dist/presets/common-preset'),
       ...corePresets,
     ],
-    overridePresets: [],
+    overridePresets: [
+      require.resolve('@storybook/core-server/dist/presets/common-override-preset'),
+    ],
     ...options,
   });
 
@@ -103,7 +105,10 @@ export async function buildStaticStandalone(options: BuildStaticStandaloneOption
       ...corePresets,
       require.resolve('@storybook/core-server/dist/presets/babel-cache-preset'),
     ],
-    overridePresets: previewBuilder.overridePresets || [],
+    overridePresets: [
+      ...(previewBuilder.overridePresets || []),
+      require.resolve('@storybook/core-server/dist/presets/common-override-preset'),
+    ],
     ...options,
   });
 

code/lib/core-server/src/presets/common-override-preset.ts

@@ -0,0 +1,14 @@
+import type { PresetProperty, StorybookConfig } from '@storybook/types';
+
+export const framework: PresetProperty<'framework', StorybookConfig> = async (config) => {
+  // This will get called with the values from the user's main config, but before
+  // framework preset from framework packages e.g. react-webpack5 gets called.
+  // This means we can add default values to the framework config, before it's requested by other packages.
+  const name = typeof config === 'string' ? config : config?.name;
+  const options = typeof config === 'string' ? {} : config?.options || {};
+
+  return {
+    name,
+    options,
+  };
+};