main can only be commonjs, not esm

Related discussion: isaacs/node-glob#557
isaacs · Sep 27, 2023 · 68d9726 · 68d9726
1 parent 3263369
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diff --git a/README.md b/README.md
@@ -164,25 +164,24 @@ package entry points.
 
 By default, tshy deletes the `main` field, rather than maintain
 this affordance for versions of node that met their end of life
-more than a year ago. However, some tools still rely on `main`
-and have not been updated to read the package entry points via
-`exports`.
+long ago. However, some tools still rely on `main` and have not
+been updated to read the package entry points via `exports`.
+
+**Warning: this will likely cause incorrect types to be loaded in
+some scenarios.**
 
-**Warning: this will likely cause incorrect types to be loaded.**
 Use with extreme caution. It's almost always better to _not_
 define top-level `main` and `types` fields if you are shipping a
 hybrid module. Users will need to update their `module` and
 `moduleResolution` tsconfigs appropriately. **That is a good
 thing, and will save them future headaches.**
 
 You can tell tshy to export a top-level `main` and `types` field
-by setting `main` to either `commonjs` or `esm`. If `main` is set
-to `"commonjs"`, then the package will not have `"type":
-"module"` set.
+by setting `main` to `true`.
 
-If the specified dialect is not built, or if a `"."` export is
+If the `commonjs` dialect is not built, or if a `"."` export is
 not created, or if the `"."` export does not support the
-specified dialect, then the build will fail.
+`commonjs` dialect, then the build will fail.
 
 For example, this config:
 
@@ -192,7 +191,7 @@ For example, this config:
     "exports": {
       ".": "./src/index.ts"
     },
-    "main": "commonjs"
+    "main": true
   }
 }
 ```
@@ -203,6 +202,7 @@ will produce:
 {
   "main": "./dist/commonjs/index.js",
   "types": "./dist/commonjs/index.d.ts",
+  "type": "module",
   "exports": {
     ".": {
       "require": {

diff --git a/src/exports.ts b/src/exports.ts
@@ -6,7 +6,6 @@ import pkg from './package.js'
 import polyfills from './polyfills.js'
 import { resolveExport } from './resolve-export.js'
 import { Export, Package, TshyConfig, TshyExport } from './types.js'
-import { isDialect } from './valid-dialects.js'
 
 export const getImpTarget = (
   s: string | TshyExport | undefined | null
@@ -94,28 +93,26 @@ export const setMain = (
   c: TshyConfig | undefined,
   pkg: Package & { exports: Record<string, Export> }
 ) => {
-  if (c?.main !== undefined) {
-    if (!isDialect(c.main)) {
-      fail(`config.main must be 'commonjs' or 'esm', got: ${c.main}`)
-      return process.exit(1)
-    }
-    const m = c.main === 'commonjs' ? 'require' : 'import'
-    const mod = resolveExport(pkg.exports['.'], [m])
+  if (!!c?.main) {
+    c.main = true
+    const mod = resolveExport(pkg.exports['.'], ['require'])
     if (!mod) {
-      fail(`could not resolve exports['.'] for tshy.main '${m}'`)
+      fail(`could not resolve exports['.'] for tshy.main 'require'`)
       return process.exit(1)
     }
-    const types = resolveExport(pkg.exports['.'], [m, 'types'])
+    const types = resolveExport(pkg.exports['.'], [
+      'require',
+      'types',
+    ])
     pkg.main = mod
-    if (c.main === 'esm') pkg.type = 'module'
-    else delete pkg.type
     if (types && types !== mod) pkg.types = types
     else delete pkg.types
   } else {
-    pkg.type = 'module'
+    if (c) delete c.main
     delete pkg.main
     delete pkg.types
   }
+  pkg.type = 'module'
 }
 
 // These are all defined by exports, so it's just confusing otherwise

diff --git a/src/types.ts b/src/types.ts
@@ -2,7 +2,7 @@ export type TshyConfig = {
   exports?: Record<string, TshyExport>
   dialects?: Dialect[]
   selfLink?: boolean
-  main?: Dialect
+  main?: boolean
 }
 
 export type Dialect = 'commonjs' | 'esm'

diff --git a/tap-snapshots/test/exports.ts.test.cjs b/tap-snapshots/test/exports.ts.test.cjs
@@ -20,35 +20,3 @@ Array [
   ],
 ]
 `
-
-exports[`test/exports.ts > TAP > setting top level main > invalid main esm > must match snapshot 1`] = `
-Array [
-  Array [
-    "could not resolve exports['.'] for tshy.main 'import'",
-  ],
-]
-`
-
-exports[`test/exports.ts > TAP > setting top level main > invalid main esm, no exports > must match snapshot 1`] = `
-Array [
-  Array [
-    "could not resolve exports['.'] for tshy.main 'import'",
-  ],
-]
-`
-
-exports[`test/exports.ts > TAP > setting top level main > invalid main=blah > must match snapshot 1`] = `
-Array [
-  Array [
-    "config.main must be 'commonjs' or 'esm', got: blah",
-  ],
-]
-`
-
-exports[`test/exports.ts > TAP > setting top level main > invalid main=false > must match snapshot 1`] = `
-Array [
-  Array [
-    "config.main must be 'commonjs' or 'esm', got: false",
-  ],
-]
-`
diff --git a/test/exports.ts b/test/exports.ts
@@ -79,7 +79,6 @@ t.test('setting top level main', async t => {
     {
       main?: string
       types?: string
-      type?: string
     },
     boolean
   ][] = [
@@ -93,13 +92,13 @@ t.test('setting top level main', async t => {
           },
         },
       },
-      { type: 'module' },
+      {},
       true,
     ],
     [
       'main commonjs',
       {
-        tshy: { main: 'commonjs' },
+        tshy: { main: true },
         exports: {
           '.': {
             require: { types: './r.d.ts', default: './r.js' },
@@ -110,24 +109,10 @@ t.test('setting top level main', async t => {
       { main: './r.js', types: './r.d.ts' },
       true,
     ],
-    [
-      'main esm',
-      {
-        tshy: { main: 'esm' },
-        exports: {
-          '.': {
-            require: { types: './r.d.ts', default: './r.js' },
-            import: { types: './i.d.ts', default: './i.js' },
-          },
-        },
-      },
-      { type: 'module', main: './i.js', types: './i.d.ts' },
-      true,
-    ],
     [
       'main commonjs, no types',
       {
-        tshy: { main: 'commonjs' },
+        tshy: { main: true },
         exports: {
           '.': {
             require: './r.js',
@@ -138,39 +123,9 @@ t.test('setting top level main', async t => {
       { main: './r.js' },
       true,
     ],
-    [
-      'main esm, no types',
-      {
-        tshy: { main: 'esm' },
-        exports: {
-          '.': {
-            require: { types: './r.d.ts', default: './r.js' },
-            import: './i.js',
-          },
-        },
-      },
-      { main: './i.js', type: 'module' },
-      true,
-    ],
-    [
-      'invalid main=blah',
-      {
-        //@ts-expect-error
-        tshy: { main: 'blah' },
-        exports: {
-          '.': {
-            require: { types: './r.d.ts', default: './r.js' },
-            import: { types: './i.d.ts', default: './i.js' },
-          },
-        },
-      },
-      {},
-      false,
-    ],
     [
       'invalid main=false',
       {
-        //@ts-expect-error
         tshy: { main: false },
         exports: {
           '.': {
@@ -180,12 +135,12 @@ t.test('setting top level main', async t => {
         },
       },
       {},
-      false,
+      true
     ],
     [
       'invalid main commonjs',
       {
-        tshy: { main: 'commonjs' },
+        tshy: { main: true },
         exports: {
           '.': {
             import: { types: './i.d.ts', default: './i.js' },
@@ -195,32 +150,10 @@ t.test('setting top level main', async t => {
       {},
       false,
     ],
-    [
-      'invalid main esm',
-      {
-        tshy: { main: 'esm' },
-        exports: {
-          '.': {
-            require: { types: './r.d.ts', default: './r.js' },
-          },
-        },
-      },
-      {},
-      false,
-    ],
     [
       'invalid main commonjs, no exports',
       {
-        tshy: { main: 'commonjs' },
-        exports: {},
-      },
-      {},
-      false,
-    ],
-    [
-      'invalid main esm, no exports',
-      {
-        tshy: { main: 'esm' },
+        tshy: { main: true },
         exports: {},
       },
       {},
@@ -243,7 +176,7 @@ t.test('setting top level main', async t => {
       if (ok) {
         t.equal(pkg.main, expect.main)
         t.equal(pkg.types, expect.types)
-        t.equal(pkg.type, expect.type)
+        t.equal(pkg.type, 'module')
       } else {
         t.strictSame(exits(), [[1]])
         t.matchSnapshot(fails)