Use python3.7 dataclass in a few places. NFC (#25191)

Author: sbc100

emcc.py

@@ -29,6 +29,7 @@
 import sys
 import time
 import tarfile
+from dataclasses import dataclass
 from enum import Enum, auto, unique
 from subprocess import PIPE
 
@@ -89,6 +90,7 @@ class Mode(Enum):
   COMPILE_AND_LINK = auto()
 
 
+@dataclass
 class LinkFlag:
   """Used to represent a linker flag.
 
@@ -97,9 +99,8 @@ class LinkFlag:
 
   A list of these is return by separate_linker_flags.
   """
-  def __init__(self, value, is_file):
-    self.value = value
-    self.is_file = is_file
+  value: str
+  is_file: int
 
 
 class EmccState:

emsymbolizer.py

@@ -14,10 +14,13 @@
 # Separate DWARF is not supported yet.
 
 import argparse
+from dataclasses import dataclass
 import json
 import re
 import subprocess
 import sys
+from typing import Optional
+
 from tools import shared
 from tools import webassembly
 
@@ -30,12 +33,12 @@ class Error(BaseException):
 
 
 # Class to treat location info in a uniform way across information sources.
+@dataclass
 class LocationInfo:
-  def __init__(self, source=None, line=0, column=0, func=None):
-    self.source = source
-    self.line = line
-    self.column = column
-    self.func = func
+  source: Optional[str] = None
+  line: int = 0
+  column: int = 0
+  func: Optional[str] = None
 
   def print(self):
     source = self.source if self.source else '??'
@@ -100,12 +103,12 @@ def get_sourceMappingURL_section(module):
 
 
 class WasmSourceMap:
+  @dataclass
   class Location:
-    def __init__(self, source=None, line=0, column=0, func=None):
-      self.source = source
-      self.line = line
-      self.column = column
-      self.func = func
+    source: Optional[str] = None
+    line: int = 0
+    column: int = 0
+    func: Optional[str] = None
 
   def __init__(self):
     self.version = None

tools/extract_metadata.py

@@ -5,6 +5,7 @@
 
 import logging
 from typing import List, Dict
+from dataclasses import dataclass
 
 from . import webassembly, utils
 from .webassembly import OpCode, AtomicOpCode, MemoryOpCode
@@ -299,6 +300,7 @@ def get_string_at(module, address):
   return data_to_string(data[offset:str_end])
 
 
+@dataclass(init=False)
 class Metadata:
   imports: List[str]
   export: List[str]
@@ -314,9 +316,6 @@ class Metadata:
   tag_exports: List[str]
   all_exports: List[str]
 
-  def __init__(self):
-    pass
-
 
 def extract_metadata(filename):
   em_js_funcs = {}

tools/file_packager.py

@@ -76,6 +76,7 @@
 import posixpath
 import shutil
 import sys
+from dataclasses import dataclass
 from subprocess import PIPE
 from textwrap import dedent
 from typing import List
@@ -123,12 +124,12 @@ def __init__(self):
     self.export_es6 = False
 
 
+@dataclass
 class DataFile:
-  def __init__(self, srcpath, dstpath, mode, explicit_dst_path):
-    self.srcpath = srcpath
-    self.dstpath = dstpath
-    self.mode = mode
-    self.explicit_dst_path = explicit_dst_path
+  srcpath: str
+  dstpath: str
+  mode: str
+  explicit_dst_path: bool
 
 
 options = Options()