bpo-22352: Adjust widths in the output of dis.dis() for large line numbers and (#1153)

instruction offsets.

Add tests for widths of opcode names.

1 files changed, 23 insertions, 7 deletions

diff --git a/Lib/dis.py b/Lib/dis.py
index f93d5b22d4..f3c18a5fde 100644
--- a/Lib/dis.py
+++ b/Lib/dis.py
@@ -175,6 +175,9 @@ _Instruction.offset.__doc__ = "Start index of operation within bytecode sequence
 _Instruction.starts_line.__doc__ = "Line started by this opcode (if any), otherwise None"
 _Instruction.is_jump_target.__doc__ = "True if other code jumps to here, otherwise False"
 
+_OPNAME_WIDTH = 20
+_OPARG_WIDTH = 5
+
 class Instruction(_Instruction):
     """Details for a bytecode operation
 
@@ -189,11 +192,12 @@ class Instruction(_Instruction):
          is_jump_target - True if other code jumps to here, otherwise False
     """
 
-    def _disassemble(self, lineno_width=3, mark_as_current=False):
+    def _disassemble(self, lineno_width=3, mark_as_current=False, offset_width=4):
         """Format instruction details for inclusion in disassembly output
 
         *lineno_width* sets the width of the line number field (0 omits it)
         *mark_as_current* inserts a '-->' marker arrow as part of the line
+        *offset_width* sets the width of the instruction offset field
         """
         fields = []
         # Column: Source code line number
@@ -214,12 +218,12 @@ class Instruction(_Instruction):
         else:
             fields.append('  ')
         # Column: Instruction offset from start of code sequence
-        fields.append(repr(self.offset).rjust(4))
+        fields.append(repr(self.offset).rjust(offset_width))
         # Column: Opcode name
-        fields.append(self.opname.ljust(20))
+        fields.append(self.opname.ljust(_OPNAME_WIDTH))
         # Column: Opcode argument
         if self.arg is not None:
-            fields.append(repr(self.arg).rjust(5))
+            fields.append(repr(self.arg).rjust(_OPARG_WIDTH))
             # Column: Opcode argument details
             if self.argrepr:
                 fields.append('(' + self.argrepr + ')')
@@ -339,8 +343,19 @@ def _disassemble_bytes(code, lasti=-1, varnames=None, names=None,
                        *, file=None, line_offset=0):
     # Omit the line number column entirely if we have no line number info
     show_lineno = linestarts is not None
-    # TODO?: Adjust width upwards if max(linestarts.values()) >= 1000?
-    lineno_width = 3 if show_lineno else 0
+    if show_lineno:
+        maxlineno = max(linestarts.values()) + line_offset
+        if maxlineno >= 1000:
+            lineno_width = len(str(maxlineno))
+        else:
+            lineno_width = 3
+    else:
+        lineno_width = 0
+    maxoffset = len(code) - 2
+    if maxoffset >= 10000:
+        offset_width = len(str(maxoffset))
+    else:
+        offset_width = 4
     for instr in _get_instructions_bytes(code, varnames, names,
                                          constants, cells, linestarts,
                                          line_offset=line_offset):
@@ -350,7 +365,8 @@ def _disassemble_bytes(code, lasti=-1, varnames=None, names=None,
         if new_source_line:
             print(file=file)
         is_current_instr = instr.offset == lasti
-        print(instr._disassemble(lineno_width, is_current_instr), file=file)
+        print(instr._disassemble(lineno_width, is_current_instr, offset_width),
+              file=file)
 
 def _disassemble_str(source, *, file=None):
     """Compile the source string, then disassemble the code object."""