fix: remove custom unescaping of static message

Since ICU message format uses apostrophe escaping, our manual unescape
becomes very troublesome. There seems to be no significant perf
degradation

Before:
```
<div> x 2,161,669 ops/sec ±7.87% (71 runs sampled)
100 x <div/> x 16,464 ops/sec ±0.71% (92 runs sampled)
100 x <FormattedNumber> x 2,421 ops/sec ±1.26% (91 runs sampled)
100 x <FormattedDate> x 903 ops/sec ±1.40% (91 runs sampled)
100 x <FormattedMessage> x 340 ops/sec ±11.89% (82 runs sampled)
100 x <FormattedMessage> with placeholder x 91.85 ops/sec ±5.76% (67 runs sampled)
100 x <FormattedMessage> with placeholder in AST form x 223 ops/sec ±3.57% (79 runs sampled)
100 x <FormattedMessage> with placeholder, cached x 505 ops/sec ±5.36% (72 runs sampled)
100 x <FormattedMessage> with placeholder, cached in AST form x 419 ops/sec ±6.04% (80 runs sampled)
```

After:
```
<div> x 2,998,677 ops/sec ±0.57% (90 runs sampled)
100 x <div/> x 15,512 ops/sec ±3.10% (87 runs sampled)
100 x <FormattedNumber> x 2,456 ops/sec ±1.51% (90 runs sampled)
100 x <FormattedDate> x 942 ops/sec ±0.99% (90 runs sampled)
100 x <FormattedMessage> x 358 ops/sec ±3.59% (82 runs sampled)
100 x <FormattedMessage> with placeholder x 103 ops/sec ±3.83% (75 runs sampled)
100 x <FormattedMessage> with placeholder in AST form x 237 ops/sec ±1.51% (82 runs sampled)
100 x <FormattedMessage> with placeholder, cached x 673 ops/sec ±2.15% (87 runs sampled)
100 x <FormattedMessage> with placeholder, cached in AST form x 485 ops/sec ±1.77% (86 runs sampled)
```

src/formatters/message.ts

@@ -15,17 +15,8 @@ const invariant: typeof invariant_ = (invariant_ as any).default || invariant_;
 import {Formatters, IntlConfig, MessageDescriptor} from '../types';
 
 import {createError, escape} from '../utils';
-import {LiteralElement, TYPE} from 'intl-messageformat-parser';
 import {FormatXMLElementFn, PrimitiveType} from 'intl-messageformat';
 
-/**
- * Escape a raw msg when we run in prod mode
- * https://github.com/formatjs/formatjs/blob/master/packages/intl-messageformat-parser/src/parser.pegjs#L155
- */
-function escapeUnformattedMessage(msg: string): string {
-  return msg.replace(/'\{(.*?)\}'/g, `{$1}`);
-}
-
 export function formatMessage(
   {
     locale,
@@ -77,21 +68,6 @@ export function formatMessage(
   invariant(id, '[React Intl] An `id` must be provided to format a message.');
 
   const message = messages && messages[id];
-  const hasValues = Object.keys(values).length > 0;
-
-  // Avoid expensive message formatting for simple messages without values. In
-  // development messages will always be formatted in case of missing values.
-  if (!hasValues && process.env.NODE_ENV === 'production') {
-    const val = message || defaultMessage || id;
-    if (typeof val === 'string') {
-      return escapeUnformattedMessage(val);
-    }
-    invariant(
-      val.length === 1 && val[0].type === TYPE.literal,
-      'Message has placeholders but no values was provided'
-    );
-    return (val[0] as LiteralElement).value;
-  }
 
   let formattedMessageParts: Array<string | object> = [];
 

test/unit/format.ts

@@ -722,11 +722,6 @@ describe('format API', () => {
       expect(formatMessage({id: 'ast_simple'})).toBe(mf.format());
     });
 
-    it('should throw if format AST message w/o values', () => {
-      process.env.NODE_ENV = 'production';
-      expect(() => formatMessage({id: 'ast_var'})).toThrow();
-    });
-
     it('formats messages with placeholders', () => {
       const {locale, messages} = config;
       const mf = new IntlMessageFormat(messages.with_arg, locale);
@@ -757,22 +752,6 @@ describe('format API', () => {
       );
     });
 
-    it('avoids formatting when no values and in production', () => {
-      const {messages} = config;
-
-      process.env.NODE_ENV = 'production';
-      expect(formatMessage({id: 'no_args'})).toBe(messages.no_args);
-      expect(state.getMessageFormat).toHaveBeenCalledTimes(0);
-
-      const values = {foo: 'foo'};
-      expect(formatMessage({id: 'no_args'}, values)).toBe(messages.no_args);
-      expect(state.getMessageFormat).toHaveBeenCalledTimes(1);
-
-      process.env.NODE_ENV = 'development';
-      expect(formatMessage({id: 'no_args'})).toBe(messages.no_args);
-      expect(state.getMessageFormat).toHaveBeenCalledTimes(2);
-    });
-
     describe('fallbacks', () => {
       it('formats message with missing named formats', () => {
         const {locale, messages} = config;