Fix compact printing of non-null assertion operators

packages/babel-generator/src/printer.ts

@@ -244,12 +244,15 @@ class Printer {
   token(str: string, maybeNewline = false): void {
     this._maybePrintInnerComments();
 
-    // space is mandatory to avoid outputting <!--
-    // http://javascript.spec.whatwg.org/#comment-syntax
     const lastChar = this.getLastChar();
     const strFirst = str.charCodeAt(0);
     if (
-      (lastChar === charCodes.exclamationMark && str === "--") ||
+      (lastChar === charCodes.exclamationMark &&
+        // space is mandatory to avoid outputting <!--
+        // http://javascript.spec.whatwg.org/#comment-syntax
+        (str === "--" ||
+          // Needs spaces to avoid changing a! == 0 to a!== 0
+          strFirst === charCodes.equalsTo)) ||
       // Need spaces for operators of the same kind to avoid: `a+++b`
       (strFirst === charCodes.plusSign && lastChar === charCodes.plusSign) ||
       (strFirst === charCodes.dash && lastChar === charCodes.dash) ||

packages/babel-generator/test/fixtures/typescript/types-non-null-assertion-compact/input.js

@@ -0,0 +1,5 @@
+let foo;
+foo! = 1;
+if (foo! === 0) {
+  console.log();
+}

packages/babel-generator/test/fixtures/typescript/types-non-null-assertion-compact/options.json

@@ -0,0 +1,5 @@
+{
+  "compact": true,
+  "sourceType": "module",
+  "plugins": ["typescript"]
+}

packages/babel-generator/test/fixtures/typescript/types-non-null-assertion-compact/output.js

@@ -0,0 +1 @@
+let foo;foo! =1;if(foo! ===0){console.log();}