1 files changed, 49 insertions, 0 deletions
diff --git a/packages/astro/src/vite-plugin-build-html/add-rollup-input.ts b/packages/astro/src/vite-plugin-build-html/add-rollup-input.ts
new file mode 100644
index 000000000..0da25ecf9
--- /dev/null
+++ b/packages/astro/src/vite-plugin-build-html/add-rollup-input.ts
@@ -0,0 +1,49 @@
+import { InputOptions } from 'rollup';
+
+function fromEntries<V>(entries: [string, V][]) {
+  const obj: Record<string, V> = {};
+  for (const [k, v] of entries) {
+    obj[k] = v;
+  }
+  return obj;
+}
+
+export function addRollupInput(
+  inputOptions: InputOptions,
+  newInputs: string[]
+): InputOptions {
+  // Add input module ids to existing input option, whether it's a string, array or object
+  // this way you can use multiple html plugins all adding their own inputs
+  if (!inputOptions.input) {
+    return { ...inputOptions, input: newInputs };
+  }
+
+  if (typeof inputOptions.input === 'string') {
+    return {
+      ...inputOptions,
+      input: [inputOptions.input, ...newInputs],
+    };
+  }
+
+  if (Array.isArray(inputOptions.input)) {
+    return {
+      ...inputOptions,
+      input: [...inputOptions.input, ...newInputs],
+    };
+  }
+
+  if (typeof inputOptions.input === 'object') {
+    return {
+      ...inputOptions,
+      input: {
+        ...inputOptions.input,
+        ...fromEntries(
+          newInputs
+            .map(i => [i.split('/').slice(-1)[0].split('.')[0], i]),
+        ),
+      },
+    };
+  }
+
+  throw new Error(`Unknown rollup input type. Supported inputs are string, array and object.`);
+}