fix: fix sourcemap generation (rewrites bun.StringJoiner) (#11288)

src/sourcemap/sourcemap.zig

@@ -11,7 +11,7 @@ const BabyList = JSAst.BabyList;
 const Logger = bun.logger;
 const strings = bun.strings;
 const MutableString = bun.MutableString;
-const Joiner = @import("../string_joiner.zig");
+const StringJoiner = bun.StringJoiner;
 const JSPrinter = bun.js_printer;
 const URL = bun.URL;
 const FileSystem = bun.fs.FileSystem;
@@ -886,9 +886,14 @@ pub const SourceMapPieces = struct {
         var current: usize = 0;
         var generated = LineColumnOffset{};
         var prev_shift_column_delta: i32 = 0;
-        var j = Joiner{};
 
-        j.push(this.prefix.items);
+        // the joiner's node allocator contains string join nodes as well as some vlq encodings
+        // it doesnt contain json payloads or source code, so 16kb is probably going to cover
+        // most applications.
+        var sfb = std.heap.stackFallback(16384, bun.default_allocator);
+        var j = StringJoiner{ .allocator = sfb.get() };
+
+        j.pushStatic(this.prefix.items);
         const mappings = this.mappings.items;
 
         while (current < mappings.len) {
@@ -938,23 +943,24 @@ pub const SourceMapPieces = struct {
                 continue;
             }
 
-            j.push(mappings[start_of_run..potential_end_of_run]);
+            j.pushStatic(mappings[start_of_run..potential_end_of_run]);
 
             assert(shift.before.lines == shift.after.lines);
 
             const shift_column_delta = shift.after.columns - shift.before.columns;
             const vlq_value = decode_result.value + shift_column_delta - prev_shift_column_delta;
             const encode = encodeVLQ(vlq_value);
-            j.push(encode.bytes[0..encode.len]);
+            j.pushCloned(encode.bytes[0..encode.len]);
             prev_shift_column_delta = shift_column_delta;
 
             start_of_run = potential_start_of_run;
         }
 
-        j.push(mappings[start_of_run..]);
-        j.push(this.suffix.items);
+        j.pushStatic(mappings[start_of_run..]);
 
-        return try j.done(allocator);
+        const str = try j.doneWithEnd(allocator, this.suffix.items);
+        bun.assert(str[0] == '{'); // invalid json
+        return str;
     }
 };
 
@@ -967,18 +973,18 @@ pub const SourceMapPieces = struct {
 // After all chunks are computed, they are joined together in a second pass.
 // This rewrites the first mapping in each chunk to be relative to the end
 // state of the previous chunk.
-pub fn appendSourceMapChunk(j: *Joiner, allocator: std.mem.Allocator, prev_end_state_: SourceMapState, start_state_: SourceMapState, source_map_: bun.string) !void {
+pub fn appendSourceMapChunk(j: *StringJoiner, allocator: std.mem.Allocator, prev_end_state_: SourceMapState, start_state_: SourceMapState, source_map_: bun.string) !void {
     var prev_end_state = prev_end_state_;
     var start_state = start_state_;
     // Handle line breaks in between this mapping and the previous one
     if (start_state.generated_line > 0) {
-        j.append(try strings.repeatingAlloc(allocator, @as(usize, @intCast(start_state.generated_line)), ';'), 0, allocator);
+        j.push(try strings.repeatingAlloc(allocator, @intCast(start_state.generated_line), ';'), allocator);
         prev_end_state.generated_column = 0;
     }
 
     var source_map = source_map_;
     if (strings.indexOfNotChar(source_map, ';')) |semicolons| {
-        j.push(source_map[0..semicolons]);
+        j.pushStatic(source_map[0..semicolons]);
         source_map = source_map[semicolons..];
         prev_end_state.generated_column = 0;
         start_state.generated_column = 0;
@@ -1009,19 +1015,18 @@ pub fn appendSourceMapChunk(j: *Joiner, allocator: std.mem.Allocator, prev_end_s
     start_state.original_line += original_line_.value;
     start_state.original_column += original_column_.value;
 
-    j.append(
+    j.push(
         appendMappingToBuffer(
             MutableString.initEmpty(allocator),
             j.lastByte(),
             prev_end_state,
             start_state,
         ).list.items,
-        0,
         allocator,
     );
 
     // Then append everything after that without modification.
-    j.push(source_map);
+    j.pushStatic(source_map);
 }
 
 const vlq_lookup_table: [256]VLQ = brk: {
@@ -1455,9 +1460,8 @@ pub fn appendMappingToBuffer(buffer_: MutableString, last_byte: u8, prev_state:
         buffer.appendCharAssumeCapacity(',');
     }
 
-    comptime var i: usize = 0;
-    inline while (i < vlq.len) : (i += 1) {
-        buffer.appendAssumeCapacity(vlq[i].bytes[0..vlq[i].len]);
+    inline for (vlq) |item| {
+        buffer.appendAssumeCapacity(item.bytes[0..item.len]);
     }
 
     return buffer;