elide base index of sections

Author: bishabosha

compiler/src/dotty/tools/dotc/core/tasty/TastyPrinter.scala

@@ -187,7 +187,7 @@ class TastyPrinter(bytes: Array[Byte], val testPickler: Boolean) {
           }
         indent -= 2
       }
-      sb.append(s"\n\nTrees (${endAddr.index - startAddr.index} bytes, starting from $base):")
+      sb.append(sectionHeader("Trees", reader, lineEnd = false))
       while (!isAtEnd) {
         printTree()
         newLine()
@@ -199,7 +199,7 @@ class TastyPrinter(bytes: Array[Byte], val testPickler: Boolean) {
     def unpickle0(reader: TastyReader)(using tastyName: NameRefs): Unit = {
       import reader.*
       val posUnpickler = new PositionUnpickler(reader, tastyName)
-      sb.append(s"\n\nPositions (${reader.endAddr.index - reader.startAddr.index} bytes, starting from $base):\n")
+      sb.append(sectionHeader("Positions", reader))
       val lineSizes = posUnpickler.lineSizes
       sb.append(s"  lines: ${lineSizes.length}\n")
       sb.append(s"  line sizes:\n")
@@ -232,7 +232,7 @@ class TastyPrinter(bytes: Array[Byte], val testPickler: Boolean) {
       import reader.*
       val comments = new CommentUnpickler(reader).comments
       if !comments.isEmpty then
-        sb.append(s"\n\nComments (${reader.endAddr.index - reader.startAddr.index} bytes, starting from $base):\n")
+        sb.append(sectionHeader("Comments", reader))
         val sorted = comments.toSeq.sortBy(_._1.index)
         for ((addr, cmt) <- sorted) {
           sb.append(treeStr("%6d".format(addr.index)))
@@ -245,7 +245,7 @@ class TastyPrinter(bytes: Array[Byte], val testPickler: Boolean) {
     import dotty.tools.tasty.TastyFormat.*
     def unpickle0(reader: TastyReader)(using nameAtRef: NameRefs): Unit = {
       import reader.*
-      sb.append(s"\n\nAttributes (${reader.endAddr.index - reader.startAddr.index} bytes, starting from $base):\n")
+      sb.append(sectionHeader("Attributes", reader))
       while !isAtEnd do
         // TODO: Should we elide attributes under testPickler? (i.e.
         //   if we add new attributes many check files will need to be updated)
@@ -290,6 +290,12 @@ class TastyPrinter(bytes: Array[Byte], val testPickler: Boolean) {
     }
   }
 
+  private final def sectionHeader(name: String, reader: TastyReader, lineEnd: Boolean = true): String =
+    val count = reader.endAddr.index - reader.startAddr.index
+    val suffix = if lineEnd then "\n" else ""
+    val base = if testPickler then "<elided base index>" else reader.base
+    s"\n\n$name ($count bytes, starting from $base):$suffix"
+
   abstract class PrinterSectionUnpickler[T](val name: String) {
     def unpickle0(reader: TastyReader)(using refs: NameRefs): T
   }

compiler/src/dotty/tools/dotc/transform/Pickler.scala

@@ -308,7 +308,7 @@ class Pickler extends Phase {
     if hasDiff(printed, checkContents) then
       output("after-printing.txt", printed)
       report.error(em"""TASTy printer difference for $cls in ${cls.source}, did not match ${check},
-                    |  output dumped in after-printing.txt, check diff with `git diff --no-index -- after-printing.txt ${check}`
+                    |  output dumped in after-printing.txt, check diff with `git diff --no-index -- $check after-printing.txt`
                     |  actual output:
                     |$printed""")
   }

tests/pos/i19806/J.tastycheck

@@ -32,7 +32,7 @@ Names (217 bytes, starting from 80):
     25: Attributes
 
 
-Trees (145 bytes, starting from 300):
+Trees (145 bytes, starting from <elided base index>):
      0: PACKAGE(142)
      3:   TERMREFpkg 1 [p]
      5:   VALDEF(11) 2 [J]
@@ -113,7 +113,7 @@ Trees (145 bytes, starting from 300):
    143:           SHAREDtype 38
    145:
 
-Positions (145 bytes, starting from 448):
+Positions (145 bytes, starting from <elided base index>):
   lines: 23
   line sizes:
      10, 0, 19, 0, 15, 0, 35, 29, 3, 0, 36, 29, 3, 0, 52, 41, 3, 0, 53, 41
@@ -155,7 +155,7 @@ Positions (145 bytes, starting from 448):
      0: 23 [<elided source file name>]
 
 
-Attributes (4 bytes, starting from 597):
+Attributes (4 bytes, starting from <elided base index>):
   JAVAattr
   OUTLINEattr
   SOURCEFILEattr 23 [<elided source file name>]