[TSX] infer props and params from getStaticPaths (#873)

* feat(tsx): automatically infer props and params from getStaticPaths

* chore: add changeset

* fix: prefix type utils with `ASTRO__`

.changeset/grumpy-spoons-rescue.md

@@ -0,0 +1,5 @@
+---
+'@astrojs/compiler': minor
+---
+
+Adds ability for TSX output to automatically infer `Astro.props` and `Astro.params` when `getStaticPaths` is used

internal/js_scanner/js_scanner.go

@@ -238,6 +238,21 @@ func HoistImports(source []byte) HoistedScripts {
 	return HoistedScripts{Hoisted: imports, HoistedLocs: importLocs, Body: body, BodyLocs: bodyLocs}
 }
 
+func HasGetStaticPaths(source []byte) bool {
+	ident := []byte("getStaticPaths")
+	if !bytes.Contains(source, ident) {
+		return false
+	}
+
+	exports := HoistExports(source)
+	for _, statement := range exports.Hoisted {
+		if bytes.Contains(statement, ident) {
+			return true
+		}
+	}
+	return false
+}
+
 type Props struct {
 	Ident     string
 	Statement string

internal/printer/print-to-tsx.go

@@ -97,7 +97,9 @@ func getTextType(n *astro.Node) TextType {
 func renderTsx(p *printer, n *Node) {
 	// Root of the document, print all children
 	if n.Type == DocumentNode {
-		props := js_scanner.GetPropsType([]byte(p.sourcetext))
+		source := []byte(p.sourcetext)
+		props := js_scanner.GetPropsType(source)
+		hasGetStaticPaths := js_scanner.HasGetStaticPaths(source)
 		hasChildren := false
 		for c := n.FirstChild; c != nil; c = c.NextSibling {
 			// This checks for the first node that comes *after* the frontmatter
@@ -134,15 +136,34 @@ func renderTsx(p *printer, n *Node) {
 			p.print("</Fragment>\n")
 		}
 		componentName := getTSXComponentName(p.opts.Filename)
+		propsIdent := props.Ident
+		paramsIdent := ""
+		if hasGetStaticPaths {
+			paramsIdent = "ASTRO__Get<ASTRO__InferredGetStaticPath, 'params'>"
+			if propsIdent == "Record<string, any>" {
+				propsIdent = "ASTRO__Get<ASTRO__InferredGetStaticPath, 'props'>"
+			}
+		}
 
-		p.print(fmt.Sprintf("export default function %s%s(_props: %s%s): any {}\n", componentName, props.Statement, props.Ident, props.Generics))
-		if props.Ident != "Record<string, any>" {
+		p.print(fmt.Sprintf("export default function %s%s(_props: %s%s): any {}\n", componentName, props.Statement, propsIdent, props.Generics))
+		if hasGetStaticPaths {
+			p.printf(`type ASTRO__ArrayElement<ArrayType extends readonly unknown[]> = ArrayType extends readonly (infer ElementType)[] ? ElementType : never;
+type ASTRO__Flattened<T> = T extends Array<infer U> ? ASTRO__Flattened<U> : T;
+type ASTRO__InferredGetStaticPath = ASTRO__Flattened<ASTRO__ArrayElement<Awaited<ReturnType<typeof getStaticPaths>>>>;
+type ASTRO__Get<T, K> = T extends undefined ? undefined : K extends keyof T ? T[K] : never;%s`, "\n")
+		}
+
+		if propsIdent != "Record<string, any>" {
 			p.printf(`/**
  * Astro global available in all contexts in .astro files
  *
  * [Astro documentation](https://docs.astro.build/reference/api-reference/#astro-global)
 */
-declare const Astro: Readonly<import('astro').AstroGlobal<%s, typeof %s>>`, props.Ident, componentName)
+declare const Astro: Readonly<import('astro').AstroGlobal<%s, typeof %s`, propsIdent, componentName)
+			if paramsIdent != "" {
+				p.printf(", %s", paramsIdent)
+			}
+			p.print(">>")
 		}
 		return
 	}

packages/compiler/test/tsx/props-and-getStaticPaths.ts

@@ -0,0 +1,79 @@
+import { convertToTSX } from '@astrojs/compiler';
+import { test } from 'uvu';
+import * as assert from 'uvu/assert';
+
+function getPrefix({
+  props = `ASTRO__Get<ASTRO__InferredGetStaticPath, 'props'>`,
+  component = '__AstroComponent_',
+  params = `ASTRO__Get<ASTRO__InferredGetStaticPath, 'params'>`,
+}: {
+  props?: string;
+  component?: string;
+  params?: string;
+} = {}) {
+  return `/**
+ * Astro global available in all contexts in .astro files
+ *
+ * [Astro documentation](https://docs.astro.build/reference/api-reference/#astro-global)
+*/
+declare const Astro: Readonly<import('astro').AstroGlobal<${props}, typeof ${component}${params ? `, ${params}` : ''}>>`;
+}
+
+function getSuffix() {
+  return `type ASTRO__ArrayElement<ArrayType extends readonly unknown[]> = ArrayType extends readonly (infer ElementType)[] ? ElementType : never;
+type ASTRO__Flattened<T> = T extends Array<infer U> ? ASTRO__Flattened<U> : T;
+type ASTRO__InferredGetStaticPath = ASTRO__Flattened<ASTRO__ArrayElement<Awaited<ReturnType<typeof getStaticPaths>>>>;
+type ASTRO__Get<T, K> = T extends undefined ? undefined : K extends keyof T ? T[K] : never;`;
+}
+
+test('explicit props definition', async () => {
+  const input = `---
+interface Props {};
+export function getStaticPaths() {
+  return {};
+}
+---
+
+<div></div>`;
+  const output =
+    '\n' +
+    `interface Props {};
+export function getStaticPaths() {
+  return {};
+}
+
+"";<Fragment>
+<div></div>
+</Fragment>
+export default function __AstroComponent_(_props: Props): any {}
+${getSuffix()}
+${getPrefix({ props: 'Props' })}`;
+  const { code } = await convertToTSX(input, { sourcemap: 'external' });
+  assert.snapshot(code, output, `expected code to match snapshot`);
+});
+
+test('inferred props', async () => {
+  const input = `---
+export function getStaticPaths() {
+  return {};
+}
+---
+
+<div></div>`;
+  const output =
+    '\n' +
+    `export function getStaticPaths() {
+  return {};
+}
+
+"";<Fragment>
+<div></div>
+</Fragment>
+export default function __AstroComponent_(_props: ASTRO__Get<ASTRO__InferredGetStaticPath, 'props'>): any {}
+${getSuffix()}
+${getPrefix()}`;
+  const { code } = await convertToTSX(input, { sourcemap: 'external' });
+  assert.snapshot(code, output, `expected code to match snapshot`);
+});
+
+test.run();