Inline _ or $ in the root of a method chain (#4621)

src/language-js/printer-estree.js

@@ -4440,10 +4440,11 @@ function printMemberChain(path, options, print) {
   //     .map(x => x)
   //
   // In order to detect those cases, we use an heuristic: if the first
-  // node is an identifier with the name starting with a capital letter.
-  // The rationale is that they are likely to be factories.
+  // node is an identifier with the name starting with a capital
+  // letter or just a sequence of _$. The rationale is that they are
+  // likely to be factories.
   function isFactory(name) {
-    return /^[A-Z]/.test(name);
+    return /^[A-Z]|^[_$]+$/.test(name);
   }
 
   // In case the Identifier is shorter than tab width, we can keep the

tests/method-chain/__snapshots__/jsfmt.spec.js.snap

@@ -607,6 +607,16 @@ Object.keys(
 .forEach(locale => {
   // ...
 });
+
+this.layoutPartsToHide = this.utils.hashset(
+	_.flatMap(this.visibilityHandlers, fn => fn())
+		.concat(this.record.resolved_legacy_visrules)
+		.filter(Boolean)
+);
+
+var jqxhr = $.ajax("example.php")
+  .done(doneFn)
+  .fail(failFn);
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Object.keys(
   availableLocales({
@@ -616,6 +626,16 @@ Object.keys(
   // ...
 });
 
+this.layoutPartsToHide = this.utils.hashset(
+  _.flatMap(this.visibilityHandlers, fn => fn())
+    .concat(this.record.resolved_legacy_visrules)
+    .filter(Boolean)
+);
+
+var jqxhr = $.ajax("example.php")
+  .done(doneFn)
+  .fail(failFn);
+
 `;
 
 exports[`logical.js 1`] = `

tests/method-chain/inline_merge.js

@@ -6,3 +6,13 @@ Object.keys(
 .forEach(locale => {
   // ...
 });
+
+this.layoutPartsToHide = this.utils.hashset(
+	_.flatMap(this.visibilityHandlers, fn => fn())
+		.concat(this.record.resolved_legacy_visrules)
+		.filter(Boolean)
+);
+
+var jqxhr = $.ajax("example.php")
+  .done(doneFn)
+  .fail(failFn);