From a5d62637c9fe019a25a8af6872868fb573acc9da Mon Sep 17 00:00:00 2001
From: Stefan Magnuson <stefan.magnuson@shopify.com>
Date: Mon, 8 Jun 2026 12:04:00 +0100
Subject: [PATCH] Preserve heredoc body when translating multi-line `T.let`
 assertions

When `T.let(...)` spans multiple lines and wraps a heredoc, the
replacement range covers the entire call including the heredoc body.
Since the value node's source range only covers the opener line
(e.g. `<<~MSG.strip`), the body and terminator were silently dropped,
producing syntactically broken Ruby.
---
 .../sorbet_assertions_to_rbs_comments.rb      | 45 ++++++++++++++++++-
 rbi/spoom.rbi                                 |  6 +++
 .../sorbet_assertions_to_rbs_comments_test.rb | 34 ++++++++++++++
 3 files changed, 84 insertions(+), 1 deletion(-)

diff --git a/lib/spoom/sorbet/translate/sorbet_assertions_to_rbs_comments.rb b/lib/spoom/sorbet/translate/sorbet_assertions_to_rbs_comments.rb
index d2ba75e4..6ad73e0f 100644
--- a/lib/spoom/sorbet/translate/sorbet_assertions_to_rbs_comments.rb
+++ b/lib/spoom/sorbet/translate/sorbet_assertions_to_rbs_comments.rb
@@ -103,10 +103,12 @@ def maybe_translate_assertion(node)
           # Otherwise, replace up to the end of the node
           end_offset = comment_end_offset || node.location.end_offset
 
+          heredoc_body = heredoc_body_within_range(value, end_offset)
+
           replacement = if node.name == :bind
             "#{rbs_annotation}#{trailing_comment}"
           else
-            "#{dedent_value(node, value)} #{rbs_annotation}#{trailing_comment}"
+            "#{dedent_value(node, value)} #{rbs_annotation}#{trailing_comment}#{heredoc_body}"
           end
 
           @rewriter << Source::Replace.new(start_offset, end_offset - 1, replacement)
@@ -212,6 +214,47 @@ def extract_trailing_comment(node)
           [" #{range.pack("C*")}", end_offset]
         end
 
+        #: (Prism::Node, Integer) -> String?
+        def heredoc_body_within_range(node, replace_end_offset)
+          heredoc_end = find_heredoc_end_offset(node)
+          return unless heredoc_end
+          return if heredoc_end > replace_end_offset
+
+          value_end = node.location.end_offset
+          opener_line_end = value_end
+          opener_line_end += 1 while opener_line_end < @ruby_bytes.size && @ruby_bytes[opener_line_end] != LINE_BREAK
+          return if opener_line_end >= @ruby_bytes.size
+
+          body_bytes = @ruby_bytes[(opener_line_end + 1)...heredoc_end] #: as !nil
+          body = body_bytes.pack("C*")
+          body.chomp! if @ruby_bytes[replace_end_offset] == LINE_BREAK
+          "\n#{body}"
+        end
+
+        #: (Prism::Node) -> Integer?
+        def find_heredoc_end_offset(node)
+          case node
+          when Prism::StringNode, Prism::InterpolatedStringNode
+            closing = node.closing_loc
+            opening = node.opening_loc
+            if closing && opening && opening.start_line != closing.start_line
+              return closing.end_offset
+            end
+          when Prism::CallNode
+            receiver = node.receiver
+            if receiver
+              result = find_heredoc_end_offset(receiver)
+              return result if result
+            end
+            node.arguments&.arguments&.each do |arg|
+              found = find_heredoc_end_offset(arg)
+              return found if found
+            end
+          end
+
+          nil
+        end
+
         #: (Prism::Node, Prism::Node) -> String
         def dedent_value(assign, value)
           if value.location.start_line == assign.location.start_line
diff --git a/rbi/spoom.rbi b/rbi/spoom.rbi
index ef1a2327..4e1bb6d7 100644
--- a/rbi/spoom.rbi
+++ b/rbi/spoom.rbi
@@ -3040,9 +3040,15 @@ class Spoom::Sorbet::Translate::SorbetAssertionsToRBSComments < ::Spoom::Sorbet:
   sig { params(node: ::Prism::Node).returns([T.nilable(::String), T.nilable(::Integer)]) }
   def extract_trailing_comment(node); end
 
+  sig { params(node: ::Prism::Node).returns(T.nilable(::Integer)) }
+  def find_heredoc_end_offset(node); end
+
   sig { params(node: ::Prism::Node).returns(T::Boolean) }
   def has_rbs_annotation?(node); end
 
+  sig { params(node: ::Prism::Node, replace_end_offset: ::Integer).returns(T.nilable(::String)) }
+  def heredoc_body_within_range(node, replace_end_offset); end
+
   sig { params(node: ::Prism::Node).returns(T::Boolean) }
   def maybe_translate_assertion(node); end
 
diff --git a/test/spoom/sorbet/translate/sorbet_assertions_to_rbs_comments_test.rb b/test/spoom/sorbet/translate/sorbet_assertions_to_rbs_comments_test.rb
index ed57d175..9ce82cc2 100644
--- a/test/spoom/sorbet/translate/sorbet_assertions_to_rbs_comments_test.rb
+++ b/test/spoom/sorbet/translate/sorbet_assertions_to_rbs_comments_test.rb
@@ -264,6 +264,40 @@ def test_translate_assigns_ignore_heredoc_values
           RB
         end
 
+        def test_translate_assigns_multiline_tlet_with_heredoc_values
+          rb = <<~RB
+            MSG = T.let(
+              <<~MSG.gsub(/[[:space:]]+/, " ").strip,
+                Do not use foo directly. Use bar instead.
+                See this guide: https://example.com/docs
+              MSG
+              String,
+            )
+
+            QUERY = T.let(
+              <<~SQL.squish.freeze,
+                SELECT id, name
+                FROM users
+                WHERE active = true
+              SQL
+              String,
+            )
+          RB
+
+          assert_equal(<<~RB, rbi_to_rbs(rb))
+            MSG = <<~MSG.gsub(/[[:space:]]+/, " ").strip #: String
+                Do not use foo directly. Use bar instead.
+                See this guide: https://example.com/docs
+              MSG
+
+            QUERY = <<~SQL.squish.freeze #: String
+                SELECT id, name
+                FROM users
+                WHERE active = true
+              SQL
+          RB
+        end
+
         def test_translate_assigns_does_not_match_bare_strings_has_heredoc
           rb = <<~RB
             a = T.let("<<~STR", String)