fix: correct main entry for relative path

lib/index.js

@@ -34,6 +34,7 @@ class PackageJson {
     'scripts',
     'funding',
     'bin',
+    'main',
   ])
 
   // npm pkg fix
@@ -47,6 +48,7 @@ class PackageJson {
     'fixDependencies',
     'devDependencies',
     'scriptpath',
+    'main',
   ])
 
   static prepareSteps = Object.freeze([
@@ -66,6 +68,7 @@ class PackageJson {
     'fillTypes',
     'normalizeData',
     'binRefs',
+    'main',
   ])
 
   // create a new empty package.json, so we can save at the given path even

lib/normalize.js

@@ -610,6 +610,16 @@ const normalize = async (pkg, { strict, steps, root, changes, allowLegacyCase })
       }
     }
   }
-}
 
+  if (steps.includes('main') && data.main) {
+    if (typeof data.main !== 'string') {
+      throw new TypeError('The "main" attribute must be of type string.')
+    }
+    const main = secureAndUnixifyPath(data.main)
+    if (main !== data.main) {
+      changes?.push(`"main" was normalized to "${main}"`)
+      data.main = main
+    }
+  }
+}
 module.exports = normalize

tap-snapshots/test/normalize.js.test.cjs

@@ -122,6 +122,19 @@ Array [
 ]
 `
 
+exports[`test/normalize.js TAP @npmcli/package-json - with changes main normalize main path - no changes > must match snapshot 1`] = `
+Array [
+  "Deleted incorrect \\"bundledDependencies\\"",
+]
+`
+
+exports[`test/normalize.js TAP @npmcli/package-json - with changes main normalize main to correct path > must match snapshot 1`] = `
+Array [
+  "Deleted incorrect \\"bundledDependencies\\"",
+  "\\"main\\" was normalized to \\"index.js\\"",
+]
+`
+
 exports[`test/normalize.js TAP @npmcli/package-json - with changes normalize bin > must match snapshot 1`] = `
 Array [
   "Deleted incorrect \\"bundledDependencies\\"",

test/normalize.js

@@ -338,6 +338,29 @@ for (const [name, testNormalize] of Object.entries(testMethods)) {
       t.has(content, { bin: undefined })
     })
 
+    t.test('main', t => {
+      if (isLegacy) {
+        return t.skip('rpj does not have configurable steps for main')
+      }
+      t.test('normalize main to correct path', async t => {
+        const { content: { main } } = await testNormalize(t, ({
+          'package.json': JSON.stringify({ main: './index.js' }),
+        }))
+        t.strictSame(main, 'index.js')
+      })
+      t.test('normalize main path - no changes', async t => {
+        const { content: { main } } = await testNormalize(t, ({
+          'package.json': JSON.stringify({ main: '.pkg/index.js' }),
+        }))
+        t.strictSame(main, '.pkg/index.js')
+      })
+      t.test('normalize main path - not a string', async t => {
+        t.rejects(testNormalize(t, ({
+          'package.json': JSON.stringify({ main: ['.pkg/index.js'] }),
+        })), { name: 'TypeError' })
+      })
+      t.end()
+    })
     t.test('skipping steps', async t => {
       if (isLegacy) {
         return t.skip('rpj does not have configurable steps')