fix: support exactOptionalPropertyTypes in plugin option types

.changeset/plugin-exact-optional-property-types.md

@@ -0,0 +1,7 @@
+---
+"@streamdown/code": patch
+"@streamdown/math": patch
+"@streamdown/mermaid": patch
+---
+
+Support `exactOptionalPropertyTypes`: add `| undefined` to optional props in the plugin option types so possibly-`undefined` values can be forwarded to `createCodePlugin`, `createMathPlugin` and `createMermaidPlugin` without type errors

.github/workflows/test.yml

@@ -32,7 +32,7 @@ jobs:
         run: pnpm build:packages
 
       - name: Check exactOptionalPropertyTypes compatibility
-        run: pnpm --filter streamdown exec tsc -p tsconfig.exact-optional.json
+        run: pnpm --filter streamdown --filter @streamdown/code --filter @streamdown/math --filter @streamdown/mermaid exec tsc -p tsconfig.exact-optional.json
 
       - name: Build Website
         run: pnpm build --filter website

packages/streamdown-code/index.ts

@@ -33,7 +33,7 @@ export interface HighlightOptions {
    * Whether the code block is still streaming. Its result is superseded by
    * the next update, so it is not cached.
    */
-  isIncomplete?: boolean;
+  isIncomplete?: boolean | undefined;
   language: BundledLanguage;
   themes: [ThemeInput, ThemeInput];
 }
@@ -75,7 +75,7 @@ export interface CodePluginOptions {
    * Default themes for syntax highlighting [light, dark]
    * @default ["github-light", "github-dark"]
    */
-  themes?: [ThemeInput, ThemeInput];
+  themes?: [ThemeInput, ThemeInput] | undefined;
 }
 
 const languageAliases = Object.fromEntries(

packages/streamdown-code/package.json

@@ -28,6 +28,7 @@
   "scripts": {
     "bench": "vitest bench --run > results.txt",
     "build": "tsup",
+    "check-types:exact-optional": "pnpm build && tsc -p tsconfig.exact-optional.json",
     "test": "vitest run",
     "test:coverage": "vitest --coverage run"
   },

packages/streamdown-code/tsconfig.exact-optional.json

@@ -0,0 +1,8 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "exactOptionalPropertyTypes": true
+  },
+  "include": ["type-tests/exact-optional-property-types.ts"],
+  "exclude": ["node_modules", "build", "dist"]
+}

packages/streamdown-code/tsconfig.json

@@ -16,5 +16,5 @@
     "noEmit": true
   },
   "include": ["**/*.ts", "**/*.tsx"],
-  "exclude": ["node_modules", "build", "dist"]
+  "exclude": ["node_modules", "build", "dist", "type-tests"]
 }

packages/streamdown-code/type-tests/exact-optional-property-types.ts

@@ -0,0 +1,27 @@
+/**
+ * Type-level regression test for `exactOptionalPropertyTypes` support.
+ *
+ * This file is type-checked with `tsconfig.exact-optional.json`
+ * (`pnpm check-types:exact-optional`) against the built declarations, with
+ * `exactOptionalPropertyTypes` enabled. It is never executed.
+ */
+import { createCodePlugin, type ThemeInput } from "../dist/index";
+
+interface CodeOptions {
+  isIncomplete?: boolean;
+  themes?: [ThemeInput, ThemeInput];
+}
+
+// Forwarding possibly-`undefined` optional props must type-check.
+export const createPlugin = (options: CodeOptions) =>
+  createCodePlugin({ themes: options.themes });
+
+export const plugin = createCodePlugin({ themes: undefined });
+
+export const highlight = (options: CodeOptions) =>
+  plugin.highlight({
+    code: "",
+    isIncomplete: options.isIncomplete,
+    language: "ts",
+    themes: plugin.getThemes(),
+  });

packages/streamdown-math/index.ts

@@ -11,7 +11,7 @@ export interface MathPlugin {
   /**
    * Get CSS styles path for math rendering
    */
-  getStyles?: () => string;
+  getStyles?: (() => string) | undefined;
   name: "katex";
   /**
    * Rehype plugin for rendering math
@@ -32,12 +32,12 @@ export interface MathPluginOptions {
    * KaTeX error color
    * @default "var(--color-muted-foreground)"
    */
-  errorColor?: string;
+  errorColor?: string | undefined;
   /**
    * Enable single dollar sign for inline math ($...$)
    * @default false
    */
-  singleDollarTextMath?: boolean;
+  singleDollarTextMath?: boolean | undefined;
 }
 
 /**

packages/streamdown-math/package.json

@@ -24,6 +24,7 @@
   ],
   "scripts": {
     "build": "tsup",
+    "check-types:exact-optional": "pnpm build && tsc -p tsconfig.exact-optional.json",
     "test": "vitest run",
     "test:coverage": "vitest --coverage run"
   },

packages/streamdown-math/tsconfig.exact-optional.json

@@ -0,0 +1,8 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "exactOptionalPropertyTypes": true
+  },
+  "include": ["type-tests/exact-optional-property-types.ts"],
+  "exclude": ["node_modules", "build", "dist"]
+}

packages/streamdown-math/tsconfig.json

@@ -16,5 +16,5 @@
     "noEmit": true
   },
   "include": ["**/*.ts", "**/*.tsx"],
-  "exclude": ["node_modules", "build", "dist"]
+  "exclude": ["node_modules", "build", "dist", "type-tests"]
 }

packages/streamdown-math/type-tests/exact-optional-property-types.ts

@@ -0,0 +1,31 @@
+/**
+ * Type-level regression test for `exactOptionalPropertyTypes` support.
+ *
+ * This file is type-checked with `tsconfig.exact-optional.json`
+ * (`pnpm check-types:exact-optional`) against the built declarations, with
+ * `exactOptionalPropertyTypes` enabled. It is never executed.
+ */
+import { createMathPlugin, type MathPlugin } from "../dist/index";
+
+interface MathOptions {
+  errorColor?: string;
+  getStyles?: () => string;
+  singleDollarTextMath?: boolean;
+}
+
+// Forwarding possibly-`undefined` optional props must type-check.
+export const createPlugin = (options: MathOptions) =>
+  createMathPlugin({
+    errorColor: options.errorColor,
+    singleDollarTextMath: options.singleDollarTextMath,
+  });
+
+export const plugin = createMathPlugin({
+  errorColor: undefined,
+  singleDollarTextMath: undefined,
+});
+
+export const withStyles = (options: MathOptions): MathPlugin => ({
+  ...plugin,
+  getStyles: options.getStyles,
+});

packages/streamdown-mermaid/index.ts

@@ -34,7 +34,7 @@ export interface MermaidPluginOptions {
   /**
    * Default Mermaid configuration
    */
-  config?: MermaidConfig;
+  config?: MermaidConfig | undefined;
 }
 
 const defaultConfig: MermaidConfig = {

packages/streamdown-mermaid/package.json

@@ -24,6 +24,7 @@
   ],
   "scripts": {
     "build": "tsup",
+    "check-types:exact-optional": "pnpm build && tsc -p tsconfig.exact-optional.json",
     "test": "vitest run",
     "test:coverage": "vitest --coverage run"
   },

packages/streamdown-mermaid/tsconfig.exact-optional.json

@@ -0,0 +1,8 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "exactOptionalPropertyTypes": true
+  },
+  "include": ["type-tests/exact-optional-property-types.ts"],
+  "exclude": ["node_modules", "build", "dist"]
+}

packages/streamdown-mermaid/tsconfig.json

@@ -16,5 +16,5 @@
     "noEmit": true
   },
   "include": ["**/*.ts", "**/*.tsx"],
-  "exclude": ["node_modules", "build", "dist"]
+  "exclude": ["node_modules", "build", "dist", "type-tests"]
 }

packages/streamdown-mermaid/type-tests/exact-optional-property-types.ts

@@ -0,0 +1,19 @@
+/**
+ * Type-level regression test for `exactOptionalPropertyTypes` support.
+ *
+ * This file is type-checked with `tsconfig.exact-optional.json`
+ * (`pnpm check-types:exact-optional`) against the built declarations, with
+ * `exactOptionalPropertyTypes` enabled. It is never executed.
+ */
+import type { MermaidConfig } from "mermaid";
+import { createMermaidPlugin } from "../dist/index";
+
+interface MermaidOptions {
+  config?: MermaidConfig;
+}
+
+// Forwarding possibly-`undefined` optional props must type-check.
+export const createPlugin = (options: MermaidOptions) =>
+  createMermaidPlugin({ config: options.config });
+
+export const plugin = createMermaidPlugin({ config: undefined });