default main=true, if a "." commonjs export exists

Fix: #8

src/config.ts

@@ -1,17 +1,26 @@
 // get the config and package and stuff
 
+import fail from './fail.js'
 import pkg from './package.js'
 import sources from './sources.js'
 import { Package, TshyConfig } from './types.js'
 import validDialects from './valid-dialects.js'
 import validExports from './valid-exports.js'
 
+const validBoolean = (e: Record<string, any>, name: string) => {
+  const v = e[name]
+  if (v === undefined || typeof v === 'boolean') return true
+  fail(`tshy.${name} must be a boolean value if specified, got: ` + v)
+  return process.exit(1)
+}
+
 const validConfig = (e: any): e is TshyConfig =>
   !!e &&
   typeof e === 'object' &&
   (e.exports === undefined || validExports(e['exports'])) &&
   (e.dialects === undefined || validDialects(e['dialects'])) &&
-  (e.selfLink === undefined || typeof e.selfLink === 'boolean')
+  validBoolean(e, 'selfLink') &&
+  validBoolean(e, 'main')
 
 const getConfig = (
   pkg: Package,

src/exports.ts

@@ -93,9 +93,9 @@ export const setMain = (
   c: TshyConfig | undefined,
   pkg: Package & { exports: Record<string, Export> }
 ) => {
-  if (!!c?.main) {
-    c.main = true
-    const mod = resolveExport(pkg.exports['.'], ['require'])
+  const mod = resolveExport(pkg.exports['.'], ['require'])
+  const main = c?.main ?? !!mod
+  if (main) {
     if (!mod) {
       fail(`could not resolve exports['.'] for tshy.main 'require'`)
       return process.exit(1)

tap-snapshots/test/config.ts.test.cjs

@@ -12,3 +12,7 @@ tshy.dialects must be an array including "esm" and/or "commonjs", got: "yolo"
 exports[`test/config.ts > TAP > {"config":{"exports":{"./blah":{"require":"./src/notallowed"}}},"sources":[],"ok":false} > must match snapshot 1`] = `
 tshy.exports ./blah unbuilt exports must not be in ./src, and exports in src must be string values. got: {"require":"./src/notallowed"}
 `
+
+exports[`test/config.ts > TAP > {"config":{"main":"blah"},"sources":[],"ok":false} > must match snapshot 1`] = `
+tshy.main must be a boolean value if specified, got: blah
+`

tap-snapshots/test/exports.ts.test.cjs

@@ -5,15 +5,15 @@
  * Make sure to inspect the output below.  Do not ignore changes!
  */
 'use strict'
-exports[`test/exports.ts > TAP > setting top level main > invalid main commonjs > must match snapshot 1`] = `
+exports[`test/exports.ts > TAP > setting top level main > invalid main commonjs, no exports > must match snapshot 1`] = `
 Array [
   Array [
     "could not resolve exports['.'] for tshy.main 'require'",
   ],
 ]
 `
 
-exports[`test/exports.ts > TAP > setting top level main > invalid main commonjs, no exports > must match snapshot 1`] = `
+exports[`test/exports.ts > TAP > setting top level main > main explicit true, no commonjs module > must match snapshot 1`] = `
 Array [
   Array [
     "could not resolve exports['.'] for tshy.main 'require'",

test/config.ts

@@ -52,6 +52,8 @@ const cases: [
       exports: { '.': './src/main.ts' },
     },
   ],
+  //@ts-expect-error
+  [{ main: 'blah' }, [], false, {}],
 ]
 
 t.plan(cases.length)

test/exports.ts

@@ -83,7 +83,7 @@ t.test('setting top level main', async t => {
     boolean
   ][] = [
     [
-      'no main set',
+      'main defaults true',
       {
         exports: {
           '.': {
@@ -92,11 +92,27 @@ t.test('setting top level main', async t => {
           },
         },
       },
+      { main: './r.js', types: './r.d.ts' },
+      true,
+    ],
+    [
+      'main explicit false, removes',
+      {
+        tshy: { main: false },
+        main: './r.js',
+        types: './r.d.ts',
+        exports: {
+          '.': {
+            require: { types: './r.d.ts', default: './r.js' },
+            import: { types: './i.d.ts', default: './i.js' },
+          },
+        },
+      },
       {},
       true,
     ],
     [
-      'main commonjs',
+      'main explicit true',
       {
         tshy: { main: true },
         exports: {
@@ -124,7 +140,7 @@ t.test('setting top level main', async t => {
       true,
     ],
     [
-      'invalid main=false',
+      'main=false, not set in pj already',
       {
         tshy: { main: false },
         exports: {
@@ -135,10 +151,23 @@ t.test('setting top level main', async t => {
         },
       },
       {},
-      true
+      true,
+    ],
+    [
+      'main not set, no commonjs main export',
+      {
+        tshy: {},
+        exports: {
+          '.': {
+            import: { types: './i.d.ts', default: './i.js' },
+          },
+        },
+      },
+      {},
+      true,
     ],
     [
-      'invalid main commonjs',
+      'main explicit true, no commonjs module',
       {
         tshy: { main: true },
         exports: {