exports field should exist in types-only builds (#210)

Author: enisdenjo

.changeset/yellow-carrots-teach.md

@@ -0,0 +1,5 @@
+---
+'bob-the-bundler': patch
+---
+
+exports field should exist in types-only builds

src/commands/build.ts

@@ -373,12 +373,10 @@ function rewritePackageJson(pkg: Record<string, any>, typesOnly: boolean) {
     definition: newPkg.typescript.definition.replace(distDirStr, ''),
   };
 
-  if (!typesOnly) {
-    if (!pkg.exports) {
-      newPkg.exports = presetFields.exports;
-    }
-    newPkg.exports = rewriteExports(pkg.exports, DIST_DIR);
+  if (!pkg.exports) {
+    newPkg.exports = presetFields.exports;
   }
+  newPkg.exports = rewriteExports(pkg.exports, DIST_DIR, typesOnly);
 
   if (pkg.bin) {
     newPkg.bin = {};
@@ -415,7 +413,10 @@ export function validatePackageJson(
     expect('module', undefined);
     expect('typings', presetFields.typings);
     expect('typescript.definition', presetFields.typescript.definition);
-    expect('exports', undefined);
+    expect("exports['.'].default", {
+      // only the "types" field is required
+      types: presetFields.exports['.'].default.types,
+    });
     return;
   }
 

src/commands/check.ts

@@ -28,6 +28,19 @@ const ExportsMapModel = zod.record(
   ]),
 );
 
+const TypesOnlyExportsMapEntry = zod.object({
+  types: zod.string(),
+});
+
+const TypesOnlyExportsMapModel = zod.record(
+  zod.union([
+    zod.string(),
+    zod.object({
+      default: TypesOnlyExportsMapEntry,
+    }),
+  ]),
+);
+
 const BinModel = zod.record(zod.string());
 
 export const checkCommand = createCommand<{}, {}>(api => {
@@ -86,20 +99,15 @@ export const checkCommand = createCommand<{}, {}>(api => {
             const distPackageJSONPath = path.join(cwd, 'dist', 'package.json');
             const distPackageJSON = await fse.readJSON(distPackageJSONPath);
 
-            // a tell for a types-only build is the lack of main import and presence of typings
-            if (distPackageJSON.main === '' && (distPackageJSON.typings || '').endsWith('d.ts')) {
-              api.reporter.warn(
-                `Skip check for '${packageJSON.name}' because it's a types-only package.`,
-              );
-              return;
-            }
-
             try {
               await checkExportsMapIntegrity({
                 cwd: path.join(cwd, 'dist'),
                 packageJSON: distPackageJSON,
                 skipExports: new Set<string>(config?.check?.skip ?? []),
                 includesCommonJS: config?.commonjs ?? true,
+                // a tell for a types-only build is the lack of main import and presence of typings
+                typesOnly:
+                  distPackageJSON.main === '' && (distPackageJSON.typings || '').endsWith('d.ts'),
               });
             } catch (err) {
               api.reporter.error(`Integrity check of '${packageJSON.name}' failed.`);
@@ -127,17 +135,39 @@ async function checkExportsMapIntegrity(args: {
   };
   skipExports: Set<string>;
   includesCommonJS: boolean;
+  typesOnly: boolean;
 }) {
-  const exportsMapResult = ExportsMapModel.safeParse(args.packageJSON['exports']);
+  const exportsMapResult = (args.typesOnly ? TypesOnlyExportsMapModel : ExportsMapModel).safeParse(
+    args.packageJSON['exports'],
+  );
   if (exportsMapResult.success === false) {
     throw new Error(
       "Missing exports map within the 'package.json'.\n" +
         exportsMapResult.error.message +
         '\nCorrect Example:\n' +
-        JSON.stringify(presetFields.exports, null, 2),
+        JSON.stringify(
+          args.typesOnly
+            ? {
+                ...presetFields.exports,
+                '.': {
+                  default: {
+                    types: presetFields.exports['.'].default.types,
+                  },
+                },
+              }
+            : presetFields.exports,
+          null,
+          2,
+        ),
     );
   }
 
+  // just check if the types under default exist
+  if (args.typesOnly) {
+    await fse.stat(path.join(args.cwd, (args.packageJSON.exports as any)?.['.']?.default?.types));
+    return;
+  }
+
   const exportsMap = exportsMapResult['data'];
 
   const cjsSkipExports = new Set<string>();

src/utils/rewrite-exports.ts

@@ -6,7 +6,11 @@ type Exports =
       default?: string | Record<string, string>;
     };
 
-export function rewriteExports(exports: Record<string, Exports>, distDir: string) {
+export function rewriteExports(
+  exports: Record<string, Exports>,
+  distDir: string,
+  typesOnly: boolean,
+) {
   const newExports = { ...exports };
 
   for (const [key, value] of Object.entries(newExports)) {
@@ -24,17 +28,24 @@ export function rewriteExports(exports: Record<string, Exports>, distDir: string
         if (typeof value === 'object') {
           const newValue: Record<string, string> = {};
           for (const [key, path] of Object.entries(value)) {
-            newValue[key] = path.replace(`${distDir}/`, '');
+            if (!typesOnly || key === 'types') {
+              // types-only builds need just the types field
+              newValue[key] = path.replace(`${distDir}/`, '');
+            }
           }
           return newValue;
         }
         return value.replace(`${distDir}/`, '');
       }
 
       newValue = {
-        require: transformValue(newValue.require),
-        import: transformValue(newValue.import),
-        default: transformValue(newValue.import),
+        ...(typesOnly
+          ? {}
+          : {
+              require: transformValue(newValue.require),
+              import: transformValue(newValue.import),
+            }),
+        default: transformValue(typesOnly ? newValue.default : newValue.import),
       };
     }
     newExports[key.replace(`${distDir}/`, '')] = newValue;

test/__fixtures__/simple-monorepo-pnpm/packages/c/package.json

@@ -1,6 +1,14 @@
 {
   "name": "c",
   "main": "",
+  "exports": {
+    ".": {
+      "default": {
+        "types": "./dist/typings/index.d.ts"
+      }
+    },
+    "./package.json": "./package.json"
+  },
   "typings": "dist/typings/index.d.ts",
   "publishConfig": {
     "directory": "dist",

test/__fixtures__/simple-monorepo/packages/c/package.json

@@ -1,6 +1,14 @@
 {
   "name": "c",
   "main": "",
+  "exports": {
+    ".": {
+      "default": {
+        "types": "./dist/typings/index.d.ts"
+      }
+    },
+    "./package.json": "./package.json"
+  },
   "typings": "dist/typings/index.d.ts",
   "publishConfig": {
     "directory": "dist",

test/__fixtures__/simple-types-only/package.json

@@ -2,6 +2,14 @@
   "name": "simple-types-only",
   "type": "module",
   "main": "",
+  "exports": {
+    ".": {
+      "default": {
+        "types": "./dist/typings/index.d.ts"
+      }
+    },
+    "./package.json": "./package.json"
+  },
   "typings": "dist/typings/index.d.ts",
   "publishConfig": {
     "directory": "dist",

test/exports.test.ts

@@ -27,6 +27,7 @@ test('basic exports', () => {
         },
       },
       'dist',
+      false,
     ),
   ).toStrictEqual({
     '.': {
@@ -96,6 +97,7 @@ test('with custom exports', () => {
         },
       },
       'dist',
+      false,
     ),
   ).toStrictEqual({
     '.': {
@@ -142,3 +144,5 @@ test('with custom exports', () => {
     },
   });
 });
+
+test.todo('with types-only exports');

test/integration.spec.ts

@@ -267,15 +267,23 @@ it('can build a monorepo project', async () => {
     }
   `);
   expect(await fse.readFile(files.c['package.json'], 'utf8')).toMatchInlineSnapshot(`
-      {
-        "name": "c",
-        "main": "",
-        "typings": "typings/index.d.ts",
-        "typescript": {
-          "definition": "typings/index.d.ts"
-        }
+    {
+      "name": "c",
+      "main": "",
+      "typings": "typings/index.d.ts",
+      "typescript": {
+        "definition": "typings/index.d.ts"
+      },
+      "exports": {
+        ".": {
+          "default": {
+            "types": "./typings/index.d.ts"
+          }
+        },
+        "./package.json": "./package.json"
       }
-    `);
+    }
+  `);
 
   await execa('node', [binaryFolder, 'check'], {
     cwd: path.resolve(fixturesFolder, 'simple-monorepo'),
@@ -345,6 +353,14 @@ it('can build a types only project', async () => {
       "typings": "typings/index.d.ts",
       "typescript": {
         "definition": "typings/index.d.ts"
+      },
+      "exports": {
+        ".": {
+          "default": {
+            "types": "./typings/index.d.ts"
+          }
+        },
+        "./package.json": "./package.json"
       }
     }
   `);
@@ -560,15 +576,23 @@ it('can build a monorepo pnpm project', async () => {
     }
   `);
   expect(await fse.readFile(files.c['package.json'], 'utf8')).toMatchInlineSnapshot(`
-      {
-        "name": "c",
-        "main": "",
-        "typings": "typings/index.d.ts",
-        "typescript": {
-          "definition": "typings/index.d.ts"
-        }
+    {
+      "name": "c",
+      "main": "",
+      "typings": "typings/index.d.ts",
+      "typescript": {
+        "definition": "typings/index.d.ts"
+      },
+      "exports": {
+        ".": {
+          "default": {
+            "types": "./typings/index.d.ts"
+          }
+        },
+        "./package.json": "./package.json"
       }
-    `);
+    }
+  `);
 
   await execa('node', [binaryFolder, 'check'], {
     cwd: path.resolve(fixturesFolder, 'simple-monorepo-pnpm'),