bug#61017: 29.0.60; ruby-ts-mode indents class between two lines incorrectly

[Dmitry Gutov <dgutov@yandex.ru>]

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Hi!

On 23/01/2023 06:33, Aaron Jensen wrote:
> 
> Start with a buffer in ruby-ts-mode like:
> 
> a
> 
> b
> 
> Between the two lines, type "class Foo", then press enter
> 
> You should get this:
> 
> a
> 
>    class Foo
> 
> b
> 
> But this is expected:
> 
> a
> 
> class Foo
> 
> b
> 
> Note that reindenting after adding the "end" will indent correctly, so
> it's only an issue with electric indent

Thanks for the report, the problem here is that such examples parse into 
a malformed syntax tree:

   (program (identifier)
    (ERROR class (constant) (identifier)))

Another example would be:

   class C
     def foo

which parses as

   (ERROR class (constant) def (identifier))

We can try to anticipate such cases and infer the implied structure 
somehow, or just disable indentation for specific cases. See the 
attached patch for the latter.

Is it enough of an improvement?

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diff --git a/lisp/progmodes/ruby-ts-mode.el b/lisp/progmodes/ruby-ts-mode.el
index f0337775d51..c3c77d68e9a 100644
--- a/lisp/progmodes/ruby-ts-mode.el
+++ b/lisp/progmodes/ruby-ts-mode.el
@@ -546,6 +546,12 @@ ruby-ts--indent-rules
            ((n-p-gp nil nil "regex") no-indent 0)
            ((parent-is "regex") no-indent 0)
 
+           ;; Incomplete buffer state, better not reindent.
+           ((and (parent-is "ERROR")
+                 (or (node-is ,ruby-ts--class-or-module-regex)
+                     (node-is "\\`def\\'")))
+            no-indent 0)
+
            ;; if then else elseif notes:
            ;;
            ;;   1. The "then" starts at the end of the line that ends