scripts/depscan: combine pickle and JSON data into a single file

We don't need to write and pass two separate files to the depscanner,
I've used the pickle because the pickle serializer/deserializer should
be faster than JSON, thought I haven't tested.

mesonbuild/backend/ninjabackend.py

@@ -144,10 +144,12 @@ class TargetDependencyScannerInfo:
     :param private_dir: The private scratch directory for the target.
     :param source2object: A mapping of source file names to the objects that
         will be created from them.
+    :param sources: A list of all the sources in this target
     """
 
     private_dir: str
     source2object: T.Dict[str, str]
+    sources: T.List[str]
 
 
 @unique
@@ -1095,25 +1097,20 @@ class NinjaBackend(backends.Backend):
         pickle_base = target.name + '.dat'
         pickle_file = os.path.join(self.get_target_private_dir(target), pickle_base).replace('\\', '/')
         pickle_abs = os.path.join(self.get_target_private_dir_abs(target), pickle_base).replace('\\', '/')
-        json_abs = os.path.join(self.get_target_private_dir_abs(target), f'{target.name}-deps.json').replace('\\', '/')
         rule_name = 'depscan'
         scan_sources = self.select_sources_to_scan(compiled_sources)
 
-        # Dump the sources as a json list. This avoids potential problems where
-        # the number of sources passed to depscan exceeds the limit imposed by
-        # the OS.
-        with open(json_abs, 'w', encoding='utf-8') as f:
-            json.dump(scan_sources, f)
-        elem = NinjaBuildElement(self.all_outputs, depscan_file, rule_name, json_abs)
-        elem.add_item('picklefile', pickle_file)
+        scaninfo = TargetDependencyScannerInfo(
+            self.get_target_private_dir(target), source2object, scan_sources)
+        with open(pickle_abs, 'wb') as p:
+            pickle.dump(scaninfo, p)
+
+        elem = NinjaBuildElement(self.all_outputs, depscan_file, rule_name, pickle_file)
         # Add any generated outputs to the order deps of the scan target, so
         # that those sources are present
         for g in generated_source_files:
             elem.orderdeps.add(g.relative_name())
         elem.orderdeps.update(object_deps)
-        scaninfo = TargetDependencyScannerInfo(self.get_target_private_dir(target), source2object)
-        with open(pickle_abs, 'wb') as p:
-            pickle.dump(scaninfo, p)
         self.add_build(elem)
 
     def select_sources_to_scan(self, compiled_sources: T.List[str]) -> T.List[str]:

mesonbuild/scripts/depscan.py

@@ -5,7 +5,6 @@
 from __future__ import annotations
 
 import collections
-import json
 import os
 import pathlib
 import pickle
@@ -32,11 +31,11 @@ FORTRAN_SUBMOD_RE = re.compile(FORTRAN_SUBMOD_PAT, re.IGNORECASE)
 FORTRAN_USE_RE = re.compile(FORTRAN_USE_PAT, re.IGNORECASE)
 
 class DependencyScanner:
-    def __init__(self, pickle_file: str, outfile: str, sources: T.List[str]):
+    def __init__(self, pickle_file: str, outfile: str):
         with open(pickle_file, 'rb') as pf:
             self.target_data: TargetDependencyScannerInfo = pickle.load(pf)
         self.outfile = outfile
-        self.sources = sources
+        self.sources = self.target_data.sources
         self.provided_by: T.Dict[str, str] = {}
         self.exports: T.Dict[str, str] = {}
         self.needs: collections.defaultdict[str, T.List[str]] = collections.defaultdict(list)
@@ -183,9 +182,7 @@ class DependencyScanner:
         return 0
 
 def run(args: T.List[str]) -> int:
-    assert len(args) == 3, 'got wrong number of arguments!'
-    pickle_file, outfile, jsonfile = args
-    with open(jsonfile, encoding='utf-8') as f:
-        sources = json.load(f)
-    scanner = DependencyScanner(pickle_file, outfile, sources)
+    assert len(args) == 2, 'got wrong number of arguments!'
+    outfile, pickle_file = args
+    scanner = DependencyScanner(pickle_file, outfile)
     return scanner.scan()