Fix formatting of let blocks in containers, and add tests

topiary-cli/tests/samples/expected/nickel.ncl

@@ -139,7 +139,17 @@
         1
       else
         3
-    )
+    ),
+    let x = 1, y = 2 in x + y,
+    let
+      x = 1,
+      y = 2,
+    in x + y,
+    let rec
+      x = 1,
+      y = 2,
+    in
+    x + y,
   ],
 
   # Nickel standard library as of 44aef1672a09a76a71946fbf822713747ab7b9df

topiary-cli/tests/samples/input/nickel.ncl

@@ -127,7 +127,19 @@ bar == 'Goodbye
           if x == 1 then
               1
 else
-    3)
+    3),
+
+    let x = 1, y = 2 in x + y,
+
+    let x = 1,
+    y = 2,
+    in x + y,
+
+    let
+    rec x = 1,
+    y = 2,
+    in
+    x + y,
   ],
 
   # Nickel standard library as of 44aef1672a09a76a71946fbf822713747ab7b9df

topiary-queries/queries/nickel.scm

@@ -589,12 +589,33 @@
   .
 )
 
+; Allow newlines after the comma (or semicolon) following a container
+; element.
 (
   (#scope_id! "container")
   [
-    ","
-    ";"
-  ] @append_spaced_scoped_softline
+    (record_field)
+    (record_last_field)
+    (field_pattern)
+    (last_field_pat)
+    (match_branch)
+    (term)
+    (pattern)
+    (last_elem_pat)
+    (enum)
+  ]
+  .
+  ["," ";"] @append_spaced_scoped_softline
+  .
+  (comment)? @do_nothing
+)
+
+; Enums and records can have a `;` at the very beginning; allow spaces after
+; these ones also.
+(_
+  (#scope_id! "container")
+  .
+  ";" @append_spaced_scoped_softline
   .
   (comment)? @do_nothing
 )