Discourage + string concatenation from FileDescriptors

protokt-codegen/src/main/kotlin/protokt/v1/codegen/generate/FileDescriptorEncoding.kt

@@ -43,14 +43,14 @@ private const val BYTES_PER_PART = BYTES_PER_LINE * LINES_PER_PART
 // This makes huge bytecode files and can easily hit the compiler's internal
 // code size limits (error "code to large").  String literals are apparently
 // embedded raw, which is what we want.
-fun encodeFileDescriptor(fileDescriptorProto: FileDescriptorProto): List<List<String>> {
-    val parts = mutableListOf<MutableList<String>>()
+fun encodeFileDescriptor(fileDescriptorProto: FileDescriptorProto): List<String> {
+    val parts = mutableListOf<String>()
     val bytes = fileDescriptorProto.toByteArray()
     for (i in bytes.indices step BYTES_PER_LINE) {
         if (i % BYTES_PER_PART == 0) {
-            parts.add(mutableListOf())
+            parts.add("")
         }
-        parts.last().add(escape(bytes.asSequence().drop(i).take(BYTES_PER_LINE)))
+        parts[parts.size - 1] += escape(bytes.asSequence().drop(i).take(BYTES_PER_LINE))
     }
     return parts
 }

protokt-codegen/src/main/kotlin/protokt/v1/codegen/generate/FileDescriptorResolver.kt

@@ -78,14 +78,11 @@ private constructor(
         return FileDescriptorInfo(type, properties)
     }
 
-    private fun descriptorLines() =
-        fileDescriptorParts()
-            .map { arrayParts ->
-                arrayParts
-                    .map { CodeBlock.of("\"%L\"", it) }
-                    .joinToCode(" +\n")
-            }
-            .joinToCode(",\n")
+    private fun descriptorLines(): CodeBlock {
+        val sb = StringBuilder()
+        fileDescriptorParts().forEach(sb::append)
+        return CodeBlock.of("\"%L\"", sb.toString().bindSpaces())
+    }
 
     private fun fileDescriptorParts() =
         encodeFileDescriptor(

protokt-codegen/src/main/kotlin/protokt/v1/codegen/generate/MessageGenerator.kt

@@ -207,7 +207,11 @@ private class MessageGenerator(
                     } else {
                         buildCodeBlock {
                             add("return \"%L(\" +\n", msg.className.simpleName)
-                            toStringLines(properties).forEach(::add)
+                            if (properties.size < 100) {
+                                toStringLines(properties).forEach(::add)
+                            } else {
+                                add(toStringLine(properties))
+                            }
                             add(unknownFieldsToString(prefix = ", "))
                         }
                     }
@@ -226,6 +230,12 @@ private class MessageGenerator(
                 prop.name
             )
         }
+
+    private fun toStringLine(properties: List<PropertyInfo>): CodeBlock {
+        val string = "\"" + properties.joinToString(", ") { "%N=\$%N" } + "\" +\n"
+        val names = properties.flatMap { listOf(it, it) }
+        return CodeBlock.of(string.bindSpaces(), *names.map { it.name }.toTypedArray())
+    }
 }
 
 fun formatDoc(lines: List<String>) =