Tweak preset-env corejs/useBuiltIns warning and error messages

packages/babel-preset-env/src/normalize-options.js

@@ -204,7 +204,17 @@ export function normalizeCoreJSOption(
   if (useBuiltIns && corejs === undefined) {
     rawVersion = 2;
     console.log(
-      "\nWith `useBuiltIns` option, required direct setting of `corejs` option\n",
+      "\nWe noticed you're using the `useBuiltIns` option without declaring a " +
+        "core-js version. Currently, we assume version 2.x when no version " +
+        "is passed. Since this default version will likely change in future " +
+        "versions of Babel, we recommend explicitly setting the core-js version " +
+        "you are using via the `corejs` option.\n" +
+        "\nYou should also be sure that the version you pass to the `corejs` " +
+        "option matches the version specified in your `package.json`'s " +
+        "`dependencies` section. If it doesn't, you need to run one of the " +
+        "following commands:\n\n" +
+        "  npm install --save core-js@2    npm install --save core-js@3\n" +
+        "  yarn add core-js@2              yarn add core-js@3\n",
     );
   } else if (typeof corejs === "object" && corejs !== null) {
     rawVersion = corejs.version;
@@ -216,11 +226,16 @@ export function normalizeCoreJSOption(
   const version = rawVersion ? coerce(String(rawVersion)) : false;
 
   if (!useBuiltIns && version) {
-    console.log("\n`corejs` option required only with `useBuiltIns` option\n");
+    console.log(
+      "\nThe `corejs` option only has an effect when the `useBuiltIns` option is not `false`\n",
+    );
   }
 
   if (useBuiltIns && (!version || version.major < 2 || version.major > 3)) {
-    throw new RangeError("Supported only core-js@2 and core-js@3.");
+    throw new RangeError(
+      "Invalid Option: The version passed to `corejs` is invalid. Currently, " +
+        "only core-js@2 and core-js@3 are supported.",
+    );
   }
 
   return { version, proposals };

packages/babel-preset-env/test/debug-fixtures/corejs-without-usebuiltins/stdout.txt

@@ -1,4 +1,4 @@
-`corejs` option required only with `useBuiltIns` option
+The `corejs` option only has an effect when the `useBuiltIns` option is not `false`
 
 @babel/preset-env: `DEBUG` option
 

packages/babel-preset-env/test/debug-fixtures/entry-no-corejs-no-import/stdout.txt

@@ -1,4 +1,9 @@
-With `useBuiltIns` option, required direct setting of `corejs` option
+We noticed you're using the `useBuiltIns` option without declaring a core-js version. Currently, we assume version 2.x when no version is passed. Since this default version will likely change in future versions of Babel, we recommend explicitly setting the core-js version you are using via the `corejs` option.
+
+You should also be sure that the version you pass to the `corejs` option matches the version specified in your `package.json`'s `dependencies` section. If it doesn't, you need to run one of the following commands:
+
+  npm install --save core-js@2    npm install --save core-js@3
+  yarn add core-js@2              yarn add core-js@3
 
 @babel/preset-env: `DEBUG` option
 

packages/babel-preset-env/test/debug-fixtures/entry-no-corejs-shippedProposals/stdout.txt

@@ -1,4 +1,9 @@
-With `useBuiltIns` option, required direct setting of `corejs` option
+We noticed you're using the `useBuiltIns` option without declaring a core-js version. Currently, we assume version 2.x when no version is passed. Since this default version will likely change in future versions of Babel, we recommend explicitly setting the core-js version you are using via the `corejs` option.
+
+You should also be sure that the version you pass to the `corejs` option matches the version specified in your `package.json`'s `dependencies` section. If it doesn't, you need to run one of the following commands:
+
+  npm install --save core-js@2    npm install --save core-js@3
+  yarn add core-js@2              yarn add core-js@3
 
 @babel/preset-env: `DEBUG` option
 

packages/babel-preset-env/test/debug-fixtures/entry-no-corejs-uglify/stdout.txt

@@ -1,4 +1,9 @@
-With `useBuiltIns` option, required direct setting of `corejs` option
+We noticed you're using the `useBuiltIns` option without declaring a core-js version. Currently, we assume version 2.x when no version is passed. Since this default version will likely change in future versions of Babel, we recommend explicitly setting the core-js version you are using via the `corejs` option.
+
+You should also be sure that the version you pass to the `corejs` option matches the version specified in your `package.json`'s `dependencies` section. If it doesn't, you need to run one of the following commands:
+
+  npm install --save core-js@2    npm install --save core-js@3
+  yarn add core-js@2              yarn add core-js@3
 
 
 The uglify target has been deprecated. Set the top level

packages/babel-preset-env/test/debug-fixtures/entry-no-corejs/stdout.txt

@@ -1,4 +1,9 @@
-With `useBuiltIns` option, required direct setting of `corejs` option
+We noticed you're using the `useBuiltIns` option without declaring a core-js version. Currently, we assume version 2.x when no version is passed. Since this default version will likely change in future versions of Babel, we recommend explicitly setting the core-js version you are using via the `corejs` option.
+
+You should also be sure that the version you pass to the `corejs` option matches the version specified in your `package.json`'s `dependencies` section. If it doesn't, you need to run one of the following commands:
+
+  npm install --save core-js@2    npm install --save core-js@3
+  yarn add core-js@2              yarn add core-js@3
 
 @babel/preset-env: `DEBUG` option
 

packages/babel-preset-env/test/debug-fixtures/usage-no-corejs-none/stdout.txt

@@ -1,4 +1,9 @@
-With `useBuiltIns` option, required direct setting of `corejs` option
+We noticed you're using the `useBuiltIns` option without declaring a core-js version. Currently, we assume version 2.x when no version is passed. Since this default version will likely change in future versions of Babel, we recommend explicitly setting the core-js version you are using via the `corejs` option.
+
+You should also be sure that the version you pass to the `corejs` option matches the version specified in your `package.json`'s `dependencies` section. If it doesn't, you need to run one of the following commands:
+
+  npm install --save core-js@2    npm install --save core-js@3
+  yarn add core-js@2              yarn add core-js@3
 
 @babel/preset-env: `DEBUG` option
 

packages/babel-preset-env/test/debug-fixtures/usage-no-corejs/stdout.txt

@@ -1,4 +1,9 @@
-With `useBuiltIns` option, required direct setting of `corejs` option
+We noticed you're using the `useBuiltIns` option without declaring a core-js version. Currently, we assume version 2.x when no version is passed. Since this default version will likely change in future versions of Babel, we recommend explicitly setting the core-js version you are using via the `corejs` option.
+
+You should also be sure that the version you pass to the `corejs` option matches the version specified in your `package.json`'s `dependencies` section. If it doesn't, you need to run one of the following commands:
+
+  npm install --save core-js@2    npm install --save core-js@3
+  yarn add core-js@2              yarn add core-js@3
 
 @babel/preset-env: `DEBUG` option
 

packages/babel-preset-env/test/normalize-options.spec.js

@@ -64,6 +64,26 @@ describe("normalize-options", () => {
         ).toThrowError(/were found in both/);
       },
     );
+
+    it("should not throw if corejs version is valid", () => {
+      [2, 2.1, 3, 3.5].forEach(corejs => {
+        ["entry", "usage"].forEach(useBuiltIns => {
+          expect(() =>
+            normalizeOptions.default({ useBuiltIns, corejs }),
+          ).not.toThrowError();
+        });
+      });
+    });
+
+    it("should throw if corejs version is invalid", () => {
+      [1, 1.2, 4, 4.5].forEach(corejs => {
+        ["entry", "usage"].forEach(useBuiltIns => {
+          expect(() =>
+            normalizeOptions.default({ useBuiltIns, corejs }),
+          ).toThrowError(/The version passed to `corejs` is invalid./);
+        });
+      });
+    });
   });
 
   describe("Config format validation", () => {