Fix multiline str pattern newline multiplication

crates/compiler/fmt/src/pattern.rs

@@ -473,6 +473,7 @@ pub fn pattern_lift_spaces<'a, 'b: 'a>(
     match pat {
         Pattern::Apply(func, args) => {
             let func_lifted = pattern_lift_spaces(arena, &func.value);
+
             let args = arena.alloc_slice_copy(args);
             let (before, func, after) = if let Some(last) = args.last_mut() {
                 let last_lifted = pattern_lift_spaces(arena, &last.value);
@@ -528,6 +529,19 @@ pub fn pattern_lift_spaces<'a, 'b: 'a>(
         Pattern::SpaceBefore(expr, spaces) => {
             let mut inner = pattern_lift_spaces(arena, expr);
             inner.before = merge_spaces(arena, spaces, inner.before);
+
+            if starts_with_block_str(&inner.item)
+                && matches!(inner.before.last(), Some(CommentOrNewline::Newline))
+            {
+                // Ick!
+                // The block string will keep "generating" newlines when formatted (it wants to start on its own line),
+                // so we strip one out here.
+                //
+                // Note that this doesn't affect Expr's because those have explicit parens, and we can control
+                // whether spaces cross that boundary.
+                inner.before = &inner.before[..inner.before.len() - 1];
+            }
+
             inner
         }
         Pattern::SpaceAfter(expr, spaces) => {
@@ -543,6 +557,17 @@ pub fn pattern_lift_spaces<'a, 'b: 'a>(
     }
 }
 
+fn starts_with_block_str(item: &Pattern<'_>) -> bool {
+    match item {
+        Pattern::As(inner, _) | Pattern::Apply(inner, _) => starts_with_block_str(&inner.value),
+        Pattern::SpaceBefore(inner, _) | Pattern::SpaceAfter(inner, _) => {
+            starts_with_block_str(inner)
+        }
+        Pattern::StrLiteral(str_literal) => is_str_multiline(str_literal),
+        _ => false,
+    }
+}
+
 pub fn pattern_lift_spaces_before<'a, 'b: 'a>(
     arena: &'a Bump,
     pat: &Pattern<'b>,

crates/compiler/test_syntax/tests/snapshots/pass/multiline_str_apply_in_parens_pat.expr.formatted.roc

@@ -0,0 +1,6 @@
+u
+    (
+    """
+    """
+        0) : f
+s

crates/compiler/test_syntax/tests/snapshots/pass/multiline_str_apply_in_parens_pat.expr.result-ast

@@ -0,0 +1,58 @@
+@0-16 SpaceAfter(
+    Defs(
+        Defs {
+            tags: [
+                EitherIndex(2147483648),
+            ],
+            regions: [
+                @0-14,
+            ],
+            space_before: [
+                Slice<roc_parse::ast::CommentOrNewline> { start: 0, length: 0 },
+            ],
+            space_after: [
+                Slice<roc_parse::ast::CommentOrNewline> { start: 0, length: 0 },
+            ],
+            spaces: [],
+            type_defs: [],
+            value_defs: [
+                Annotation(
+                    @0-1 Apply(
+                        @0-1 Identifier {
+                            ident: "u",
+                        },
+                        [
+                            @2-11 Apply(
+                                @2-8 StrLiteral(
+                                    Block(
+                                        [],
+                                    ),
+                                ),
+                                [
+                                    @9-10 NumLiteral(
+                                        "0",
+                                    ),
+                                ],
+                            ),
+                        ],
+                    ),
+                    @13-14 BoundVariable(
+                        "f",
+                    ),
+                ),
+            ],
+        },
+        @15-16 SpaceBefore(
+            Var {
+                module_name: "",
+                ident: "s",
+            },
+            [
+                Newline,
+            ],
+        ),
+    ),
+    [
+        Newline,
+    ],
+)

crates/compiler/test_syntax/tests/snapshots/pass/multiline_str_apply_in_parens_pat.expr.roc

@@ -0,0 +1,2 @@
+u(""""""(0)):f
+s

crates/compiler/test_syntax/tests/test_snapshots.rs

@@ -471,6 +471,7 @@ mod test_snapshots {
         pass/multiline_apply_equals_multiline_apply.expr,
         pass/multiline_backpassing.expr,
         pass/multiline_binop_when_with_comments.expr,
+        pass/multiline_str_apply_in_parens_pat.expr,
         pass/multiline_str_crazyness.expr,
         pass/multiline_str_in_pat.expr,
         pass/multiline_str_opt_field.expr,