fix bun by pre-installing it and adding a test for it:

deployer.Dockerfile

@@ -60,7 +60,8 @@ RUN git clone https://github.com/asdf-vm/asdf.git $HOME/.asdf --branch v0.14.0 &
     asdf install erlang $DEFAULT_ERLANG_VERSION && asdf global erlang $DEFAULT_ERLANG_VERSION && \
     asdf install elixir $DEFAULT_ELIXIR_VERSION && asdf global elixir $DEFAULT_ELIXIR_VERSION && \
     # bun
-    asdf plugin add bun https://github.com/cometkim/asdf-bun.git
+    asdf plugin add bun https://github.com/cometkim/asdf-bun.git && \
+    asdf install bun $DEFAULT_BUN_VERSION && asdf global bun $DEFAULT_BUN_VERSION
 
 ENV MIX_ENV=dev
 

test/deployer/deployer_test.go

@@ -155,6 +155,31 @@ func TestLaunchBasicNode(t *testing.T) {
 	require.Equal(t, string(body), "Hello, World!")
 }
 
+func TestLaunchBasicBun(t *testing.T) {
+	deploy := testDeployer(t,
+		withFixtureApp("bun-basic"),
+		createRandomApp,
+		testlib.WithoutCustomize,
+		testlib.WithouExtensions,
+		testlib.OptOutGithubActions,
+		testlib.DeployNow,
+		withWorkDirAppSource,
+	)
+
+	manifest, err := deploy.Output().ArtifactManifest()
+	require.NoError(t, err)
+	require.NotNil(t, manifest)
+
+	require.Equal(t, manifest.Plan.Runtime.Language, "bun")
+
+	appName := deploy.Extra["appName"].(string)
+
+	body, err := testlib.RunHealthCheck(fmt.Sprintf("https://%s.fly.dev", appName))
+	require.NoError(t, err)
+
+	require.Equal(t, string(body), "Hello, Bun!")
+}
+
 func TestLaunchGoFromRepo(t *testing.T) {
 	deploy := testDeployer(t,
 		createRandomApp,

test/fixtures/bun-basic/.gitignore

@@ -0,0 +1,175 @@
+# Based on https://raw.githubusercontent.com/github/gitignore/main/Node.gitignore
+
+# Logs
+
+logs
+_.log
+npm-debug.log_
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+.pnpm-debug.log*
+
+# Caches
+
+.cache
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+
+report.[0-9]_.[0-9]_.[0-9]_.[0-9]_.json
+
+# Runtime data
+
+pids
+_.pid
+_.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+
+lib-cov
+
+# Coverage directory used by tools like istanbul
+
+coverage
+*.lcov
+
+# nyc test coverage
+
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+
+bower_components
+
+# node-waf configuration
+
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+
+build/Release
+
+# Dependency directories
+
+node_modules/
+jspm_packages/
+
+# Snowpack dependency directory (https://snowpack.dev/)
+
+web_modules/
+
+# TypeScript cache
+
+*.tsbuildinfo
+
+# Optional npm cache directory
+
+.npm
+
+# Optional eslint cache
+
+.eslintcache
+
+# Optional stylelint cache
+
+.stylelintcache
+
+# Microbundle cache
+
+.rpt2_cache/
+.rts2_cache_cjs/
+.rts2_cache_es/
+.rts2_cache_umd/
+
+# Optional REPL history
+
+.node_repl_history
+
+# Output of 'npm pack'
+
+*.tgz
+
+# Yarn Integrity file
+
+.yarn-integrity
+
+# dotenv environment variable files
+
+.env
+.env.development.local
+.env.test.local
+.env.production.local
+.env.local
+
+# parcel-bundler cache (https://parceljs.org/)
+
+.parcel-cache
+
+# Next.js build output
+
+.next
+out
+
+# Nuxt.js build / generate output
+
+.nuxt
+dist
+
+# Gatsby files
+
+# Comment in the public line in if your project uses Gatsby and not Next.js
+
+# https://nextjs.org/blog/next-9-1#public-directory-support
+
+# public
+
+# vuepress build output
+
+.vuepress/dist
+
+# vuepress v2.x temp and cache directory
+
+.temp
+
+# Docusaurus cache and generated files
+
+.docusaurus
+
+# Serverless directories
+
+.serverless/
+
+# FuseBox cache
+
+.fusebox/
+
+# DynamoDB Local files
+
+.dynamodb/
+
+# TernJS port file
+
+.tern-port
+
+# Stores VSCode versions used for testing VSCode extensions
+
+.vscode-test
+
+# yarn v2
+
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+.pnp.*
+
+# IntelliJ based IDEs
+.idea
+
+# Finder (MacOS) folder config
+.DS_Store

test/fixtures/bun-basic/README.md

@@ -0,0 +1,15 @@
+# bun-basic
+
+To install dependencies:
+
+```bash
+bun install
+```
+
+To run:
+
+```bash
+bun run index.ts
+```
+
+This project was created using `bun init` in bun v1.1.3. [Bun](https://bun.sh) is a fast all-in-one JavaScript runtime.

test/fixtures/bun-basic/index.ts

@@ -0,0 +1,5 @@
+Bun.serve({
+    fetch(req) {
+      return new Response("Hello, Bun!");
+    },
+  });

test/fixtures/bun-basic/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "bun-basic",
+  "module": "index.ts",
+  "type": "module",
+  "devDependencies": {
+    "@types/bun": "latest"
+  },
+  "peerDependencies": {
+    "typescript": "^5.0.0"
+  }
+}

test/fixtures/bun-basic/tsconfig.json

@@ -0,0 +1,27 @@
+{
+  "compilerOptions": {
+    // Enable latest features
+    "lib": ["ESNext", "DOM"],
+    "target": "ESNext",
+    "module": "ESNext",
+    "moduleDetection": "force",
+    "jsx": "react-jsx",
+    "allowJs": true,
+
+    // Bundler mode
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "verbatimModuleSyntax": true,
+    "noEmit": true,
+
+    // Best practices
+    "strict": true,
+    "skipLibCheck": true,
+    "noFallthroughCasesInSwitch": true,
+
+    // Some stricter flags (disabled by default)
+    "noUnusedLocals": false,
+    "noUnusedParameters": false,
+    "noPropertyAccessFromIndexSignature": false
+  }
+}