Indent arrows’ expression bodies like function bodies (Bug#25904)

* lisp/progmodes/js.el (js--continued-expression-p): Don’t confuse
‘=>’ for a ‘>’ operator.
(js--line-terminating-arrow-re): New variable.
(js--looking-at-broken-arrow-function-p): New function.
(js--proper-indentation): Don’t align arrow functions’ expression
bodies starting on new lines like list continuations, instead align
them like function bodies (js-indent-align-list-continuation need not
be nil).

* test/manual/indent/js.js: Add test for Bug#25904.

Co-authored-by: Felipe Ochoa <felipe@fov.space>

1 files changed, 9 insertions, 0 deletions

diff --git a/test/manual/indent/js.js b/test/manual/indent/js.js
index df790986947..647d7438f45 100644
--- a/test/manual/indent/js.js
+++ b/test/manual/indent/js.js
@@ -151,6 +151,15 @@ let b = {
   `
 }
 
+// bug#25904
+foo.bar.baz(very => // A comment
+  very
+).biz(([baz={a: [123]}, boz]) =>
+  baz
+).snarf((snorf) => /* Another comment */
+  snorf
+);
+
 // Local Variables:
 // indent-tabs-mode: nil
 // js-indent-level: 2