Support let blocks in nickel

CHANGELOG.md

@@ -58,6 +58,7 @@ This name should be decided amongst the team before the release.
 - [#711](https://github.com/tweag/topiary/pull/711) Feature gate all grammars, with supported and contributed languages built by default.
 - [#716](https://github.com/tweag/topiary/pull/716) Dynamicly fetch, compile, and load language grammars. Topiary now no longer ships with statically linked grammars.
 - [#732](https://github.com/tweag/topiary/pull/732) Change how function application and parenthesized expressions are treated in Nickel to reduce the overall noise and indentation
+- [#736](https://github.com/tweag/topiary/pull/668) Updates our Nickel grammar, and adds support for let blocks.
 
 ## v0.4.0 - Exquisite Elm - 2024-05-15
 

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

@@ -153,6 +153,16 @@
     in
     foo
     @ [],
+    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

@@ -142,6 +142,18 @@ else
 in
 foo
 @ [],
+
+    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-config/languages.ncl

@@ -43,7 +43,7 @@
       extensions = ["ncl"],
       grammar = {
         git = "https://github.com/nickel-lang/tree-sitter-nickel",
-        rev = "43433d8477b24cd13acaac20a66deda49b7e2547",
+        rev = "88d836a24b3b11c8720874a1a9286b8ae838d30a",
       },
     },
 

topiary-queries/queries/nickel.scm

@@ -295,6 +295,14 @@
 ;
 ;   let [rec] IDENT = EXPR in EXPR
 ;
+; or
+;
+;   let [rec]
+;     IDENT = EXPR,
+;     IDENT = EXPR,
+;   in
+;   EXPR
+;
 ; The formatting for the bound expression is handled by the above rules,
 ; which also apply to record field values. The "in" should appear on a
 ; new line, if the entire let expression is multi-line. The result
@@ -303,14 +311,43 @@
 ; expression, to avoid long diagonals in a series of let expressions
 ; (which is idiomatic).
 
+; A let block containing multiple bindings. If this is multiline, the first
+; binding should appear on a new line, and the bindings should be indented.
 (let_expr
   (#scope_id! "let_result")
   (let_in_block
+    "let"
+    .
+    ; Prepend before the first binding instead of appending after the "let",
+    ; so that in the case of a "let rec" the line break goes after the "rec".
+    (let_binding) @prepend_spaced_softline @prepend_indent_start
+    (let_binding)
+    "in" @prepend_indent_end @prepend_begin_scope @prepend_spaced_softline
+  )
+  (term) @append_end_scope
+)
+
+; A let with a single binding. The binding should be on the same line as the "let".
+(let_expr
+  (#scope_id! "let_result")
+  (let_in_block
+    "let"
+    .
+    (let_binding)
+    .
     "in" @prepend_begin_scope @prepend_spaced_softline
   )
   (term) @append_end_scope
 )
 
+; When binding multiple values in a let block, allow new lines between the bindings.
+(let_expr
+  (#scope_id! "let_result")
+  (let_in_block
+    ("," @append_spaced_softline)
+  )
+)
+
 (let_expr
   (#scope_id! "let_result")
   (term) @prepend_spaced_scoped_softline
@@ -603,12 +640,33 @@
   .
 )
 
+; 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
 )