programs: Allow excluding certain paths when searching in PATH

5 files changed, 54 insertions, 42 deletions

diff --git a/mesonbuild/dependencies/configtool.py b/mesonbuild/dependencies/configtool.py
index ef106a8b0..476f7ad42 100644
--- a/mesonbuild/dependencies/configtool.py
+++ b/mesonbuild/dependencies/configtool.py
@@ -37,7 +37,7 @@ class ConfigToolDependency(ExternalDependency):
     allow_default_for_cross = False
     __strip_version = re.compile(r'^[0-9][0-9.]+')
 
-    def __init__(self, name: str, environment: 'Environment', kwargs: T.Dict[str, T.Any], language: T.Optional[str] = None):
+    def __init__(self, name: str, environment: 'Environment', kwargs: T.Dict[str, T.Any], language: T.Optional[str] = None, exclude_paths: T.Optional[T.List[str]] = None):
         super().__init__(DependencyTypeName('config-tool'), environment, kwargs, language=language)
         self.name = name
         # You may want to overwrite the class version in some cases
@@ -52,7 +52,7 @@ class ConfigToolDependency(ExternalDependency):
             req_version = mesonlib.stringlistify(req_version_raw)
         else:
             req_version = []
-        tool, version = self.find_config(req_version, kwargs.get('returncode_value', 0))
+        tool, version = self.find_config(req_version, kwargs.get('returncode_value', 0), exclude_paths=exclude_paths)
         self.config = tool
         self.is_found = self.report_config(version, req_version)
         if not self.is_found:
@@ -84,15 +84,17 @@ class ConfigToolDependency(ExternalDependency):
         version = self._sanitize_version(out.strip())
         return valid, version
 
-    def find_config(self, versions: T.List[str], returncode: int = 0) \
+    def find_config(self, versions: T.List[str], returncode: int = 0, exclude_paths: T.Optional[T.List[str]] = None) \
             -> T.Tuple[T.Optional[T.List[str]], T.Optional[str]]:
         """Helper method that searches for config tool binaries in PATH and
         returns the one that best matches the given version requirements.
         """
+        exclude_paths = [] if exclude_paths is None else exclude_paths
         best_match: T.Tuple[T.Optional[T.List[str]], T.Optional[str]] = (None, None)
         for potential_bin in find_external_program(
                 self.env, self.for_machine, self.tool_name,
-                self.tool_name, self.tools, allow_default_for_cross=self.allow_default_for_cross):
+                self.tool_name, self.tools, exclude_paths=exclude_paths,
+                allow_default_for_cross=self.allow_default_for_cross):
             if not potential_bin.found():
                 continue
             tool = potential_bin.get_command()
diff --git a/mesonbuild/dependencies/ui.py b/mesonbuild/dependencies/ui.py
index cc17377a6..d88af7945 100644
--- a/mesonbuild/dependencies/ui.py
+++ b/mesonbuild/dependencies/ui.py
@@ -68,7 +68,7 @@ class GnuStepDependency(ConfigToolDependency):
             ['--gui-libs' if 'gui' in self.modules else '--base-libs'],
             'link_args'))
 
-    def find_config(self, versions: T.Optional[T.List[str]] = None, returncode: int = 0) -> T.Tuple[T.Optional[T.List[str]], T.Optional[str]]:
+    def find_config(self, versions: T.Optional[T.List[str]] = None, returncode: int = 0, exclude_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.Optional[T.List[str]], T.Optional[str]]:
         tool = [self.tools[0]]
         try:
             p, out = Popen_safe(tool + ['--help'])[:2]
diff --git a/mesonbuild/interpreter/interpreter.py b/mesonbuild/interpreter/interpreter.py
index eceb40a6b..aa839da36 100644
--- a/mesonbuild/interpreter/interpreter.py
+++ b/mesonbuild/interpreter/interpreter.py
@@ -816,7 +816,7 @@ class Interpreter(InterpreterBase, HoldableObject):
                 cmd = cmd.absolute_path(srcdir, builddir)
             # Prefer scripts in the current source directory
             search_dir = os.path.join(srcdir, self.subdir)
-            prog = ExternalProgram(cmd, silent=True, search_dir=search_dir)
+            prog = ExternalProgram(cmd, silent=True, search_dirs=[search_dir])
             if not prog.found():
                 raise InterpreterException(f'Program or command {cmd!r} not found or not executable')
             cmd = prog
@@ -1586,7 +1586,7 @@ class Interpreter(InterpreterBase, HoldableObject):
                 return prog
         return None
 
-    def program_from_system(self, args: T.List[mesonlib.FileOrString], search_dirs: T.List[str],
+    def program_from_system(self, args: T.List[mesonlib.FileOrString], search_dirs: T.Optional[T.List[str]],
                             extra_info: T.List[mlog.TV_Loggable]) -> T.Optional[ExternalProgram]:
         # Search for scripts relative to current subdir.
         # Do not cache found programs because find_program('foobar')
@@ -1601,15 +1601,15 @@ class Interpreter(InterpreterBase, HoldableObject):
                     search_dir = os.path.join(self.environment.get_source_dir(),
                                               exename.subdir)
                 exename = exename.fname
-                extra_search_dirs = []
+                search_dirs = [search_dir]
             elif isinstance(exename, str):
-                search_dir = source_dir
-                extra_search_dirs = search_dirs
+                if search_dirs:
+                    search_dirs = [source_dir] + search_dirs
+                else:
+                    search_dirs = [source_dir]
             else:
                 raise InvalidArguments(f'find_program only accepts strings and files, not {exename!r}')
-            extprog = ExternalProgram(exename, search_dir=search_dir,
-                                      extra_search_dirs=extra_search_dirs,
-                                      silent=True)
+            extprog = ExternalProgram(exename, search_dirs=search_dirs, silent=True)
             if extprog.found():
                 extra_info.append(f"({' '.join(extprog.get_command())})")
                 return extprog
@@ -1681,7 +1681,7 @@ class Interpreter(InterpreterBase, HoldableObject):
     def program_lookup(self, args: T.List[mesonlib.FileOrString], for_machine: MachineChoice,
                        default_options: T.Optional[T.Dict[OptionKey, T.Union[str, int, bool, T.List[str]]]],
                        required: bool,
-                       search_dirs: T.List[str],
+                       search_dirs: T.Optional[T.List[str]],
                        wanted: T.Union[str, T.List[str]],
                        version_arg: T.Optional[str],
                        version_func: T.Optional[ProgramVersionFunc],
diff --git a/mesonbuild/programs.py b/mesonbuild/programs.py
index bbe8ea421..9ad38e126 100644
--- a/mesonbuild/programs.py
+++ b/mesonbuild/programs.py
@@ -25,14 +25,20 @@ if T.TYPE_CHECKING:
 
 class ExternalProgram(mesonlib.HoldableObject):
 
-    """A program that is found on the system."""
+    """A program that is found on the system.
+    :param name: The name of the program
+    :param command: Optionally, an argument list constituting the command. Used when
+              you already know the command and do not want to search.
+    :param silent: Whether to print messages when initializing
+    :param search_dirs: A list of directories to search in first, followed by PATH
+    :param exclude_paths: A list of directories to exclude when searching in PATH"""
 
     windows_exts = ('exe', 'msc', 'com', 'bat', 'cmd')
     for_machine = MachineChoice.BUILD
 
     def __init__(self, name: str, command: T.Optional[T.List[str]] = None,
-                 silent: bool = False, search_dir: T.Optional[str] = None,
-                 extra_search_dirs: T.Optional[T.List[str]] = None):
+                 silent: bool = False, search_dirs: T.Optional[T.List[T.Optional[str]]] = None,
+                 exclude_paths: T.Optional[T.List[str]] = None):
         self.name = name
         self.path: T.Optional[str] = None
         self.cached_version: T.Optional[str] = None
@@ -51,13 +57,10 @@ class ExternalProgram(mesonlib.HoldableObject):
                 else:
                     self.command = [cmd] + args
         else:
-            all_search_dirs = [search_dir]
-            if extra_search_dirs:
-                all_search_dirs += extra_search_dirs
-            for d in all_search_dirs:
-                self.command = self._search(name, d)
-                if self.found():
-                    break
+            if search_dirs is None:
+                # For compat with old behaviour
+                search_dirs = [None]
+            self.command = self._search(name, search_dirs, exclude_paths)
 
         if self.found():
             # Set path to be the last item that is actually a file (in order to
@@ -242,7 +245,7 @@ class ExternalProgram(mesonlib.HoldableObject):
                         return [trial_ext]
         return None
 
-    def _search_windows_special_cases(self, name: str, command: str) -> T.List[T.Optional[str]]:
+    def _search_windows_special_cases(self, name: str, command: T.Optional[str], exclude_paths: T.Optional[T.List[str]]) -> T.List[T.Optional[str]]:
         '''
         Lots of weird Windows quirks:
         1. PATH search for @name returns files with extensions from PATHEXT,
@@ -278,31 +281,37 @@ class ExternalProgram(mesonlib.HoldableObject):
         # On Windows, interpreted scripts must have an extension otherwise they
         # cannot be found by a standard PATH search. So we do a custom search
         # where we manually search for a script with a shebang in PATH.
-        search_dirs = self._windows_sanitize_path(os.environ.get('PATH', '')).split(';')
+        search_dirs = OrderedSet(self._windows_sanitize_path(os.environ.get('PATH', '')).split(';'))
+        if exclude_paths:
+            search_dirs.difference_update(exclude_paths)
         for search_dir in search_dirs:
             commands = self._search_dir(name, search_dir)
             if commands:
                 return commands
         return [None]
 
-    def _search(self, name: str, search_dir: T.Optional[str]) -> T.List[T.Optional[str]]:
+    def _search(self, name: str, search_dirs: T.List[T.Optional[str]], exclude_paths: T.Optional[T.List[str]]) -> T.List[T.Optional[str]]:
         '''
-        Search in the specified dir for the specified executable by name
+        Search in the specified dirs for the specified executable by name
         and if not found search in PATH
         '''
-        commands = self._search_dir(name, search_dir)
-        if commands:
-            return commands
+        for search_dir in search_dirs:
+            commands = self._search_dir(name, search_dir)
+            if commands:
+                return commands
         # If there is a directory component, do not look in PATH
         if os.path.dirname(name) and not os.path.isabs(name):
             return [None]
         # Do a standard search in PATH
-        path = os.environ.get('PATH', None)
+        path = os.environ.get('PATH', os.defpath)
         if mesonlib.is_windows() and path:
             path = self._windows_sanitize_path(path)
+        if exclude_paths:
+            paths = OrderedSet(path.split(os.pathsep)).difference(exclude_paths)
+            path = os.pathsep.join(paths)
         command = shutil.which(name, path=path)
         if mesonlib.is_windows():
-            return self._search_windows_special_cases(name, command)
+            return self._search_windows_special_cases(name, command, exclude_paths)
         # On UNIX-like platforms, shutil.which() is enough to find
         # all executables whether in PATH or with an absolute path
         return [command]
@@ -341,15 +350,16 @@ class OverrideProgram(ExternalProgram):
     """A script overriding a program."""
 
     def __init__(self, name: str, version: str, command: T.Optional[T.List[str]] = None,
-                 silent: bool = False, search_dir: T.Optional[str] = None,
-                 extra_search_dirs: T.Optional[T.List[str]] = None):
+                 silent: bool = False, search_dirs: T.Optional[T.List[T.Optional[str]]] = None,
+                 exclude_paths: T.Optional[T.List[str]] = None):
         self.cached_version = version
         super().__init__(name, command=command, silent=silent,
-                         search_dir=search_dir, extra_search_dirs=extra_search_dirs)
+                         search_dirs=search_dirs, exclude_paths=exclude_paths)
 
 def find_external_program(env: 'Environment', for_machine: MachineChoice, name: str,
                           display_name: str, default_names: T.List[str],
-                          allow_default_for_cross: bool = True) -> T.Generator['ExternalProgram', None, None]:
+                          allow_default_for_cross: bool = True,
+                          exclude_paths: T.Optional[T.List[str]] = None) -> T.Generator['ExternalProgram', None, None]:
     """Find an external program, checking the cross file plus any default options."""
     potential_names = OrderedSet(default_names)
     potential_names.add(name)
@@ -367,8 +377,8 @@ def find_external_program(env: 'Environment', for_machine: MachineChoice, name:
     # Fallback on hard-coded defaults, if a default binary is allowed for use
     # with cross targets, or if this is not a cross target
     if allow_default_for_cross or not (for_machine is MachineChoice.HOST and env.is_cross_build(for_machine)):
-        for potential_path in default_names:
-            mlog.debug(f'Trying a default {display_name} fallback at', potential_path)
-            yield ExternalProgram(potential_path, silent=True)
+        for potential_name in default_names:
+            mlog.debug(f'Trying a default {display_name} fallback at', potential_name)
+            yield ExternalProgram(potential_name, silent=True, exclude_paths=exclude_paths)
     else:
         mlog.debug('Default target is not allowed for cross use')
diff --git a/unittests/failuretests.py b/unittests/failuretests.py
index baa592047..8a802120b 100644
--- a/unittests/failuretests.py
+++ b/unittests/failuretests.py
@@ -34,10 +34,10 @@ def no_pkgconfig():
     old_which = shutil.which
     old_search = ExternalProgram._search
 
-    def new_search(self, name, search_dir):
+    def new_search(self, name, search_dirs, exclude_paths):
         if name == 'pkg-config':
             return [None]
-        return old_search(self, name, search_dir)
+        return old_search(self, name, search_dirs, exclude_paths)
 
     def new_which(cmd, *kwargs):
         if cmd == 'pkg-config':