feat(eslint-plugin-formatjs): add no-multiple-whitespaces rule

This prevents usage of multiple consecutive whitespaces in message.

- Consecutive whitespaces are handled differently in different locales.
- Prevents `\` linebreaks in JS string which results in awkward whitespaces.

```tsx
import {defineMessages} from 'react-intl';

const messages = defineMessages({
  // WORKS
  foo: {
    defaultMessage: 'Smileys & People',
  },
  // FAILS
  bar: {
    defaultMessage: 'Smileys &   People',
  },
  // FAILS
  baz: {
    defaultMessage: 'this message is too long \
    so I wanna line break it.',
  },
});
```

Author: Long Ho

packages/eslint-plugin-formatjs/README.md

@@ -283,6 +283,35 @@ const messages = defineMessages({
 });
 ```
 
+## `no-multiple-whitespaces`
+
+This prevents usage of multiple consecutive whitespaces in message.
+
+#### Why
+
+- Consecutive whitespaces are handled differently in different locales.
+- Prevents `\` linebreaks in JS string which results in awkward whitespaces.
+
+```tsx
+import {defineMessages} from 'react-intl';
+
+const messages = defineMessages({
+  // WORKS
+  foo: {
+    defaultMessage: 'Smileys & People',
+  },
+  // FAILS
+  bar: {
+    defaultMessage: 'Smileys &   People',
+  },
+  // FAILS
+  baz: {
+    defaultMessage: 'this message is too long \
+    so I wanna line break it.',
+  },
+});
+```
+
 ### `no-multiple-plurals`
 
 This prevents specifying multiple plurals in your message.

packages/eslint-plugin-formatjs/src/index.ts

@@ -8,6 +8,7 @@ import blacklistElements from './rules/blacklist-elements';
 import enforcePluralRules from './rules/enforce-plural-rules';
 import enforcePlaceholders from './rules/enforce-placeholders';
 import enforceSupportedDateTimeSkeleton from './rules/supported-datetime-skeleton';
+import noMultipleWhitespaces from './rules/no-multiple-whitespaces';
 const plugin = {
   rules: {
     'enforce-description': enforceDescription,
@@ -20,6 +21,7 @@ const plugin = {
     'enforce-plural-rules': enforcePluralRules,
     'enforce-placeholders': enforcePlaceholders,
     'supported-datetime-skeleton': enforceSupportedDateTimeSkeleton,
+    'no-multiple-whitespaces': noMultipleWhitespaces,
   },
 };
 

packages/eslint-plugin-formatjs/src/rules/no-multiple-whitespaces.ts

@@ -0,0 +1,71 @@
+import {Rule, Scope} from 'eslint';
+import {ImportDeclaration, Node} from 'estree';
+import {extractMessages} from '../util';
+const MULTIPLE_SPACES = /\s{2,}/g;
+
+function checkNode(
+  context: Rule.RuleContext,
+  node: Node,
+  importedMacroVars: Scope.Variable[]
+) {
+  const msgs = extractMessages(node, importedMacroVars);
+
+  for (const [
+    {
+      message: {defaultMessage},
+      messageNode,
+    },
+  ] of msgs) {
+    if (!defaultMessage || !messageNode) {
+      continue;
+    }
+    let reportObject: Parameters<typeof context['report']>[0] | undefined;
+    if (MULTIPLE_SPACES.test(defaultMessage)) {
+      reportObject = {
+        node: messageNode,
+        message: 'Multiple consecutive whitespaces are not allowed',
+      };
+      if (messageNode.type === 'Literal' && messageNode.raw) {
+        reportObject.fix = function(fixer) {
+          return fixer.replaceText(
+            messageNode,
+            messageNode.raw!.replace(MULTIPLE_SPACES, ' ')
+          );
+        };
+      }
+      if (reportObject) {
+        context.report(reportObject);
+      }
+    }
+  }
+}
+
+const rule: Rule.RuleModule = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'Disallow emojis in message',
+      category: 'Errors',
+      recommended: false,
+      url:
+        'https://github.com/formatjs/formatjs/tree/master/packages/eslint-plugin-formatjs#no-emoji',
+    },
+    fixable: 'whitespace',
+  },
+  create(context) {
+    let importedMacroVars: Scope.Variable[] = [];
+    return {
+      ImportDeclaration: node => {
+        const moduleName = (node as ImportDeclaration).source.value;
+        if (moduleName === '@formatjs/macro' || moduleName === 'react-intl') {
+          importedMacroVars = context.getDeclaredVariables(node);
+        }
+      },
+      JSXOpeningElement: (node: Node) =>
+        checkNode(context, node, importedMacroVars),
+      CallExpression: node => checkNode(context, node, importedMacroVars),
+    };
+  },
+};
+
+export default rule;

packages/eslint-plugin-formatjs/tests/index.test.ts

@@ -198,6 +198,52 @@ _({
   ],
 });
 
+ruleTester.run('no-multiple-whitespaces', rules['no-multiple-whitespaces'], {
+  valid: [
+    `import {_} from '@formatjs/macro'
+_({
+    defaultMessage: 'a {placeholder}',
+    description: 'asd'
+})`,
+    dynamicMessage,
+    noMatch,
+    spreadJsx,
+    emptyFnCall,
+  ],
+  invalid: [
+    {
+      code:
+        "import {_} from '@formatjs/macro';_({defaultMessage: 'a \
+                {placeHolder}'})",
+      errors: [
+        {
+          message: 'Multiple consecutive whitespaces are not allowed',
+        },
+      ],
+    },
+    {
+      code: "<FormattedMessage defaultMessage='a   thing'/>",
+      errors: [
+        {
+          message: 'Multiple consecutive whitespaces are not allowed',
+        },
+      ],
+    },
+    {
+      code: `
+            import {_} from '@formatjs/macro'
+            _({
+                defaultMessage: 'a   {placeHolder}'
+            })`,
+      errors: [
+        {
+          message: 'Multiple consecutive whitespaces are not allowed',
+        },
+      ],
+    },
+  ],
+});
+
 ruleTester.run('no-multiple-plurals', rules['no-multiple-plurals'], {
   valid: [
     `import {_} from '@formatjs/macro'