minstall: raise explicit errors, by using MesonException

RuntimeError is way too generic when we have an explicit class for
"Meson reports to the user, something went wrong".

Moreover we now tell people that generic exceptions are "Meson bugs and
should be reported", so our failure to do the technically correct thing
and report the right kind of exception means we get haunted by demons of
confusion. Specifically, people complain to us that Meson told them
"there is a bug in Meson" when their install fails due to meson.build or
build environment issues.

mesonbuild/minstall.py

@@ -32,7 +32,7 @@ from .backend.backends import (
 )
 from .coredata import major_versions_differ, MesonVersionMismatchException
 from .coredata import version as coredata_version
-from .mesonlib import Popen_safe, RealPathAction, is_windows, setup_vsenv
+from .mesonlib import MesonException, Popen_safe, RealPathAction, is_windows, setup_vsenv
 from .scripts import depfixer, destdir_join
 from .scripts.meson_exe import run_exe
 try:
@@ -386,13 +386,13 @@ class Installer:
                     makedirs: T.Optional[T.Tuple[T.Any, str]] = None) -> bool:
         outdir = os.path.split(to_file)[0]
         if not os.path.isfile(from_file) and not os.path.islink(from_file):
-            raise RuntimeError(f'Tried to install something that isn\'t a file: {from_file!r}')
+            raise MesonException(f'Tried to install something that isn\'t a file: {from_file!r}')
         # copyfile fails if the target file already exists, so remove it to
         # allow overwriting a previous install. If the target is not a file, we
         # want to give a readable error.
         if os.path.exists(to_file):
             if not os.path.isfile(to_file):
-                raise RuntimeError(f'Destination {to_file!r} already exists and is not a file')
+                raise MesonException(f'Destination {to_file!r} already exists and is not a file')
             if self.should_preserve_existing_file(from_file, to_file):
                 append_to_log(self.lf, f'# Preserving old file {to_file}\n')
                 self.preserved_file_count += 1
@@ -424,10 +424,10 @@ class Installer:
         if not os.path.isabs(target):
             abs_target = os.path.join(full_dst_dir, target)
         if not os.path.exists(abs_target):
-            raise RuntimeError(f'Tried to install symlink to missing file {abs_target}')
+            raise MesonException(f'Tried to install symlink to missing file {abs_target}')
         if os.path.exists(link):
             if not os.path.islink(link):
-                raise RuntimeError(f'Destination {link!r} already exists and is not a symlink')
+                raise MesonException(f'Destination {link!r} already exists and is not a symlink')
             self.remove(link)
         if not self.printed_symlink_error:
             self.log(f'Installing symlink pointing to {target} to {link}')
@@ -670,7 +670,7 @@ class Installer:
                     self.log(f'File {t.fname!r} not found, skipping')
                     continue
                 else:
-                    raise RuntimeError(f'File {t.fname!r} could not be found')
+                    raise MesonException(f'File {t.fname!r} could not be found')
             file_copied = False # not set when a directory is copied
             fname = check_for_stampfile(t.fname)
             outdir = get_destdir_path(destdir, fullprefix, t.outdir)
@@ -682,7 +682,7 @@ class Installer:
             install_name_mappings = t.install_name_mappings
             install_mode = t.install_mode
             if not os.path.exists(fname):
-                raise RuntimeError(f'File {fname!r} could not be found')
+                raise MesonException(f'File {fname!r} could not be found')
             elif os.path.isfile(fname):
                 file_copied = self.do_copyfile(fname, outname, makedirs=(dm, outdir))
                 self.set_mode(outname, install_mode, d.install_umask)