Add blog post for v3.9 (#19414)

Co-authored-by: Alexander Kachkaev <alexander@kachkaev.ru>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

changelog_unreleased/blog-post-intro.md

@@ -0,0 +1,18 @@
+---
+authors: "fisker"
+title: "Prettier 3.9: New Parser Foundations and Formatting Improvements"
+---
+
+We are excited to announce Prettier 3.9!
+
+This release brings major parser upgrades for Markdown, YAML, Flow, GraphQL, and Angular, along with formatting improvements for JavaScript and TypeScript (particularly in `--no-semi` mode).
+
+If you find Prettier valuable, please consider [sponsoring us on OpenCollective](https://opencollective.com/prettier) or supporting the upstream projects we rely on. Your contributions help us keep improving the tool for everyone.
+
+Thank you for your continued support! ❤️
+
+A reminder, when Prettier is installed or updated, it’s [strongly recommended](https://prettier.io/docs/install#summary) to specify the exact version in `package.json`: `"prettier": "3.9.0"`, not `"prettier": "^3.9.0"`.
+
+If you use [`@prettier/plugin-oxc`](https://www.npmjs.com/package/@prettier/plugin-oxc) or [`@prettier/plugin-hermes`](https://www.npmjs.com/package/@prettier/plugin-hermes), don't forget upgrade them to ensure the new formatting rules are applied.
+
+<!-- truncate -->

changelog_unreleased/flow/19398-2.md

@@ -0,0 +1,15 @@
+#### Preserve Flow comment syntax (#19398 by @SamChou19815)
+
+Preserves Flow comment syntax annotations instead of printing them as regular Flow syntax.
+
+<!-- prettier-ignore -->
+```flow
+// Input
+function foo<T>(bar /*: T[] */, baz /*: T */) /*: S */ {}
+
+// Prettier stable
+function foo<T>(bar: T[], baz: T): S {}
+
+// Prettier main
+function foo<T>(bar /*: T[] */, baz /*: T */) /*: S */ {}
+```

changelog_unreleased/flow/19398.md

@@ -1,15 +1,5 @@
-#### Preserve Flow comment syntax and improve parser performance (#19398 by @SamChou19815)
+#### [HIGHLIGHT] New Rust-based Flow parser (#19398 by @SamChou19815)
 
-Prettier now uses Flow's Rust-backed parser. This preserves Flow comment syntax annotations instead of printing them as regular Flow syntax. In local parser-only benchmarks, `flow-parser/oxidized` parsed Prettier's valid Flow fixtures in 266.4ms median time, compared with 422.6ms for the old parser, and parsed `flow_parser.js` in 1298.0ms, compared with 2269.6ms.
+Prettier now uses the new Rust-based Flow parser (oxidized) released by the Flow team, which improves performance for Flow-typed code.
 
-<!-- prettier-ignore -->
-```flow
-// Input
-function foo<T>(bar /*: T[] */, baz /*: T */) /*: S */ {}
-
-// Prettier stable
-function foo<T>(bar: T[], baz: T): S {}
-
-// Prettier main
-function foo<T>(bar /*: T[] */, baz /*: T */) /*: S */ {}
-```
+In local parser-only benchmarks, `flow-parser/oxidized` parsed Prettier's valid Flow fixtures in 266.4ms median time, compared with 422.6ms for the old parser, and parsed `flow_parser.js` in 1298.0ms, compared with 2269.6ms.

changelog_unreleased/graphql/19171.md

@@ -1,17 +0,0 @@
-#### Support "directives on directive definitions" (#19171 by @YBJ0000)
-
-[Directives on directive definitions](https://github.com/graphql/graphql-js/pull/4521) (and `extend directive` extensions) are now supported.
-
-<!-- prettier-ignore -->
-```gql
-# Input
-directive @a @b on QUERY
-extend directive @a @b
-
-# Prettier stable
-Error: Syntax Error: Expected "on", found "@".
-
-# Prettier main
-directive @a @b on QUERY
-extend directive @a @b
-```

changelog_unreleased/graphql/19297.md

@@ -1,6 +1,8 @@
-#### Support "Fragment arguments" (#19297 by @fisker)
+#### [HIGHLIGHT] Support GraphQL.js v17 (#19171 by @YBJ0000, #19297 by @fisker)
 
-[Fragment arguments](https://github.com/graphql/graphql-js/pull/4015) are now supported.
+Prettier now fully supports newer syntax features from GraphQL.js v17, including directives on directive definitions, fragment arguments, and other enhancements.
+
+[Fragment arguments](https://github.com/graphql/graphql-js/pull/4015)
 
 <!-- prettier-ignore -->
 ```gql
@@ -11,13 +13,25 @@ fragment variableProfilePic on User {
 
 # Prettier stable
 SyntaxError: Syntax Error: Expected Name, found "(". (2:23)
-  1 | fragment variableProfilePic on User {
-> 2 |   ...dynamicProfilePic(size: $size)
-    |                       ^
-  3 | }
 
 # Prettier main
 fragment variableProfilePic on User {
   ...dynamicProfilePic(size: $size)
 }
 ```
+
+[Directives on directive definitions](https://github.com/graphql/graphql-js/pull/4521) (and `extend directive` extensions)
+
+<!-- prettier-ignore -->
+```gql
+# Input
+directive @a @b on QUERY
+extend directive @a @b
+
+# Prettier stable
+Error: Syntax Error: Expected "on", found "@".
+
+# Prettier main
+directive @a @b on QUERY
+extend directive @a @b
+```

changelog_unreleased/markdown/18277.md

@@ -1,5 +1,7 @@
 #### [HIGHLIGHT] Upgrade parser to latest micromark (#18277 by @seiyab, @j-f1, @fisker)
 
-We've upgraded Prettier's Markdown parser from the outdated remark-parse v8 to the modern micromark v4. This upgrade significantly enhances CommonMark and GFM compliance, resolves numerous long-standing parsing bugs, and lays a stronger foundation for future enhancements.
+We've upgraded Prettier's Markdown parser from the outdated `remark-parse` v8 to the modern `micromark` v4. This upgrade significantly enhances CommonMark and GFM compliance, resolves numerous long-standing parsing bugs, and lays a stronger foundation for future enhancements.
 
-A huge thank you to @seiyab for their tremendous effort in driving this major upgrade!
+Huge thanks to [@seiyab](https://github.com/seiyab), [@j-f1](https://github.com/j-f1), and everyone else who contributed to this long-awaited improvement for their tremendous effort in driving this major upgrade!
+
+**Note**: While the core Markdown parser has been upgraded, [the MDX parser upgrade](https://github.com/prettier/prettier/pull/18533) is not yet complete. If you're familiar with the unified ecosystem, micromark, or MDX, we'd love your help to finish the migration — contributions are very welcome!

changelog_unreleased/misc/19014.md

@@ -1,4 +1,4 @@
-#### updating `Printer` interface (#19014 by @Janther)
+#### Update `Printer` interface (#19014 by @Janther)
 
 ```diff
 export interface Printer<T = any> {

changelog_unreleased/yaml/18419.md

@@ -0,0 +1,5 @@
+#### [HIGHLIGHT] Update dependency `yaml` to v2 (#18419 by @ota-meshi, @fisker)
+
+The YAML parser has been upgraded to use `yaml` v2, which fixes many long standing parse issues.
+
+Thanks to excellent work on the [`yaml-unist-parser`](https://github.com/prettier/yaml-unist-parser/pull/301) side by [@ota-meshi](https://github.com/ota-meshi).