feat(v11): Drop TypeScript 3.8 support

Minimum supported TypeScript is now 5.0, so remove the downlevel-dts
type path and the TS 3.8 test surface:
- drop each package's typesVersions "<5.0" mapping and the
  build:types:downlevel step (build:types is just tsc now)
- remove downlevel-dts and the ts3.8 shim scripts/type-shims
- bump the node integration-test TS matrix to 5.0 (use-ts-5_0)
- drop the TS 3.8 e2e variants and the generic-ts3.8 app
- use the built-in Awaited type instead of the vendored shim

Author: logaretm

.github/workflows/build.yml

@@ -801,7 +801,7 @@ jobs:
         include:
           # Only check typescript for latest version (to streamline CI)
           - node: 24
-            typescript: '3.8'
+            typescript: '5.0'
           # No need to test orchestrion for v18
           - node: 20
             use_orchestrion: 'true'
@@ -826,8 +826,8 @@ jobs:
           dependency_cache_key: ${{ needs.job_build.outputs.dependency_cache_key }}
 
       - name: Overwrite typescript version
-        if: matrix.typescript == '3.8'
-        run: node ./scripts/use-ts-3_8.js
+        if: matrix.typescript == '5.0'
+        run: node ./scripts/use-ts-5_0.js
         working-directory: dev-packages/node-integration-tests
 
       - name: Run integration tests
@@ -875,7 +875,7 @@ jobs:
         include:
           # Only check typescript for latest version (to streamline CI)
           - node: 24
-            typescript: '3.8'
+            typescript: '5.0'
     steps:
       - name: Check out current commit (${{ needs.job_get_metadata.outputs.commit_label }})
         uses: actions/checkout@v7
@@ -891,8 +891,8 @@ jobs:
           dependency_cache_key: ${{ needs.job_build.outputs.dependency_cache_key }}
 
       - name: Overwrite typescript version
-        if: matrix.typescript == '3.8'
-        run: node ./scripts/use-ts-3_8.js
+        if: matrix.typescript == '5.0'
+        run: node ./scripts/use-ts-5_0.js
         working-directory: dev-packages/node-core-integration-tests
 
       - name: Run integration tests

dev-packages/e2e-tests/test-applications/create-react-app/package.json

@@ -19,7 +19,6 @@
     "eject": "react-scripts eject",
     "clean": "npx rimraf node_modules pnpm-lock.yaml",
     "test:build": "pnpm install && pnpm build",
-    "test:build-ts3.8": "pnpm install && pnpm add typescript@3.8 && pnpm build",
     "test:build-canary": "pnpm install && pnpm add react@canary react-dom@canary && pnpm build",
     "test:assert": "pnpm -v"
   },
@@ -43,13 +42,5 @@
   },
   "volta": {
     "extends": "../../package.json"
-  },
-  "sentryTest": {
-    "variants": [
-      {
-        "build-command": "pnpm test:build-ts3.8",
-        "label": "create-react-app (TS 3.8)"
-      }
-    ]
   }
 }

dev-packages/e2e-tests/test-applications/generic-ts3.8/index.ts

@@ -19,7 +19,6 @@
     "test": "playwright test",
     "clean": "npx rimraf node_modules pnpm-lock.yaml",
     "test:build": "pnpm install && pnpm build",
-    "test:build-ts3.8": "pnpm install && pnpm add typescript@3.8 && pnpm build",
     "test:build-canary": "pnpm install && pnpm add react@canary react-dom@canary && pnpm build",
     "test:assert": "pnpm test"
   },

dev-packages/e2e-tests/test-applications/generic-ts3.8/package.json

@@ -21,7 +21,6 @@
     "test": "playwright test",
     "clean": "npx rimraf node_modules pnpm-lock.yaml",
     "test:build": "pnpm install && npx playwright install && pnpm build",
-    "test:build-ts3.8": "pnpm install && pnpm add typescript@3.8 && npx playwright install && pnpm build",
     "test:build-canary": "pnpm install && pnpm add react@canary react-dom@canary && npx playwright install && pnpm build",
     "test:assert": "pnpm test"
   },

dev-packages/e2e-tests/test-applications/generic-ts3.8/tsconfig.json

@@ -18,7 +18,6 @@
     "test": "playwright test",
     "clean": "npx rimraf node_modules pnpm-lock.yaml",
     "test:build": "pnpm install && pnpm build",
-    "test:build-ts3.8": "pnpm install && pnpm add typescript@3.8 && pnpm build",
     "test:build-canary": "pnpm install && pnpm add react@canary react-dom@canary && pnpm build",
     "test:assert": "pnpm test"
   },

dev-packages/e2e-tests/test-applications/react-17/package.json

@@ -21,7 +21,6 @@
     "test": "playwright test",
     "clean": "npx rimraf node_modules pnpm-lock.yaml",
     "test:build": "pnpm install && pnpm build",
-    "test:build-ts3.8": "pnpm install && pnpm add typescript@3.8 && pnpm build",
     "test:build-canary": "pnpm install && pnpm add react@canary react-dom@canary && pnpm build",
     "test:assert": "pnpm test"
   },
@@ -51,13 +50,5 @@
   },
   "volta": {
     "extends": "../../package.json"
-  },
-  "sentryTest": {
-    "variants": [
-      {
-        "build-command": "pnpm test:build-ts3.8",
-        "label": "react-router-6 (TS 3.8)"
-      }
-    ]
   }
 }

dev-packages/e2e-tests/test-applications/react-router-6-descendant-routes/package.json

@@ -19,7 +19,6 @@
     "test": "playwright test",
     "clean": "npx rimraf node_modules pnpm-lock.yaml",
     "test:build": "pnpm install && npx playwright install && pnpm build",
-    "test:build-ts3.8": "pnpm install && pnpm add typescript@3.8 && npx playwright install && pnpm build",
     "test:build-canary": "pnpm install && pnpm add react@canary react-dom@canary && npx playwright install && pnpm build",
     "test:assert": "pnpm test"
   },