Recover when coredata cannot be loaded

Write command line options into a separate file to be able to
reconfigure from scatch in the case coredata cannot be loaded. The most
common case is when we are reconfiguring with a newer meson version.

This means that we should try as much as possible to maintain backward
compatibility for the cmd_line.txt file format.

The main difference with a normal reconfigure is it will use new
default options values and will read again environment variables like
CFLAGS, etc.

4 files changed, 68 insertions, 9 deletions

diff --git a/mesonbuild/coredata.py b/mesonbuild/coredata.py
index 819481b..cdfed7c 100644
--- a/mesonbuild/coredata.py
+++ b/mesonbuild/coredata.py
@@ -22,6 +22,7 @@ from .mesonlib import default_libdir, default_libexecdir, default_prefix
 from .wrap import WrapMode
 import ast
 import argparse
+import configparser
 
 version = '0.48.999'
 backendlist = ['ninja', 'vs', 'vs2010', 'vs2015', 'vs2017', 'xcode']
@@ -459,6 +460,45 @@ class CoreData:
             sub = 'In subproject {}: '.format(subproject) if subproject else ''
             mlog.warning('{}Unknown options: "{}"'.format(sub, unknown_options))
 
+def get_cmd_line_file(build_dir):
+    return os.path.join(build_dir, 'meson-private', 'cmd_line.txt')
+
+def read_cmd_line_file(build_dir, options):
+    filename = get_cmd_line_file(build_dir)
+    config = configparser.ConfigParser()
+    config.read(filename)
+
+    # Do a copy because config is not really a dict. options.cmd_line_options
+    # overrides values from the file.
+    d = dict(config['options'])
+    d.update(options.cmd_line_options)
+    options.cmd_line_options = d
+
+    properties = config['properties']
+    if options.cross_file is None:
+        options.cross_file = properties.get('cross_file', None)
+
+def write_cmd_line_file(build_dir, options):
+    filename = get_cmd_line_file(build_dir)
+    config = configparser.ConfigParser()
+
+    properties = {}
+    if options.cross_file is not None:
+        properties['cross_file'] = options.cross_file
+
+    config['options'] = options.cmd_line_options
+    config['properties'] = properties
+    with open(filename, 'w') as f:
+        config.write(f)
+
+def update_cmd_line_file(build_dir, options):
+    filename = get_cmd_line_file(build_dir)
+    config = configparser.ConfigParser()
+    config.read(filename)
+    config['options'].update(options.cmd_line_options)
+    with open(filename, 'w') as f:
+        config.write(f)
+
 def load(build_dir):
     filename = os.path.join(build_dir, 'meson-private', 'coredata.dat')
     load_fail_msg = 'Coredata file {!r} is corrupted. Try with a fresh build tree.'.format(filename)
@@ -470,7 +510,8 @@ def load(build_dir):
     if not isinstance(obj, CoreData):
         raise MesonException(load_fail_msg)
     if obj.version != version:
-        raise MesonException('Build directory has been generated with Meson version %s, which is incompatible with current version %s.\nPlease delete this build directory AND create a new one.' %
+        raise MesonException('Build directory has been generated with Meson version %s, '
+                             'which is incompatible with current version %s.\n' %
                              (obj.version, version))
     return obj
 
diff --git a/mesonbuild/environment.py b/mesonbuild/environment.py
index a002aa1..8891b5c 100644
--- a/mesonbuild/environment.py
+++ b/mesonbuild/environment.py
@@ -17,7 +17,7 @@ import configparser, os, platform, re, sys, shlex, shutil, subprocess
 from . import coredata
 from .linkers import ArLinker, ArmarLinker, VisualStudioLinker, DLinker
 from . import mesonlib
-from .mesonlib import EnvironmentException, PerMachine, Popen_safe
+from .mesonlib import MesonException, EnvironmentException, PerMachine, Popen_safe
 from . import mlog
 
 from . import compilers
@@ -317,13 +317,17 @@ class Environment:
             self.coredata = coredata.load(self.get_build_dir())
             self.first_invocation = False
         except FileNotFoundError:
-            # WARNING: Don't use any values from coredata in __init__. It gets
-            # re-initialized with project options by the interpreter during
-            # build file parsing.
-            self.coredata = coredata.CoreData(options)
-            # Used by the regenchecker script, which runs meson
-            self.coredata.meson_command = mesonlib.meson_command
-            self.first_invocation = True
+            self.create_new_coredata(options)
+        except MesonException as e:
+            # If we stored previous command line options, we can recover from
+            # a broken/outdated coredata.
+            if os.path.isfile(coredata.get_cmd_line_file(self.build_dir)):
+                mlog.warning('Regenerating configuration from scratch.')
+                mlog.log('Reason:', mlog.red(str(e)))
+                coredata.read_cmd_line_file(self.build_dir, options)
+                self.create_new_coredata(options)
+            else:
+                raise e
         self.exe_wrapper = None
 
         self.machines = MachineInfos()
@@ -389,6 +393,15 @@ class Environment:
         else:
             self.native_strip_bin = ['strip']
 
+    def create_new_coredata(self, options):
+        # WARNING: Don't use any values from coredata in __init__. It gets
+        # re-initialized with project options by the interpreter during
+        # build file parsing.
+        self.coredata = coredata.CoreData(options)
+        # Used by the regenchecker script, which runs meson
+        self.coredata.meson_command = mesonlib.meson_command
+        self.first_invocation = True
+
     def is_cross_build(self):
         return self.cross_info is not None
 
diff --git a/mesonbuild/mconf.py b/mesonbuild/mconf.py
index 576c574..d0f837d 100644
--- a/mesonbuild/mconf.py
+++ b/mesonbuild/mconf.py
@@ -153,6 +153,7 @@ def run(options):
         save = False
         if len(options.cmd_line_options) > 0:
             c.set_options(options.cmd_line_options)
+            coredata.update_cmd_line_file(builddir, options)
             save = True
         elif options.clearcache:
             c.clear_cache()
diff --git a/mesonbuild/msetup.py b/mesonbuild/msetup.py
index 4256272..df6ba46 100644
--- a/mesonbuild/msetup.py
+++ b/mesonbuild/msetup.py
@@ -168,6 +168,10 @@ class MesonApp:
             build.save(b, dumpfile)
             # Post-conf scripts must be run after writing coredata or else introspection fails.
             intr.backend.run_postconf_scripts()
+            if env.first_invocation:
+                coredata.write_cmd_line_file(self.build_dir, self.options)
+            else:
+                coredata.update_cmd_line_file(self.build_dir, self.options)
         except:
             if 'cdf' in locals():
                 old_cdf = cdf + '.prev'