Allow override_find_program to use an executable.

With this it is now possible to do

foobar = executable('foobar', ...)
meson.override_find_program('foobar', foobar)

Which is convenient for a project like protobuf which produces both a
dependency and a tool. If protobuf is updated to use
override_find_program, it can be used as

protobuf_dep = dependency('protobuf', version : '>=3.3.1',
                          fallback : ['protobuf', 'protobuf_dep'])
protoc_prog = find_program('protoc')

3 files changed, 17 insertions, 5 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index efe58f8..585a8d3 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -1314,6 +1314,10 @@ class Executable(BuildTarget):
         # Only linkwithable if using export_dynamic
         self.is_linkwithable = self.export_dynamic
 
+    def description(self):
+        '''Human friendly description of the executable'''
+        return self.name
+
     def type_suffix(self):
         return "@exe"
 
diff --git a/mesonbuild/dependencies/base.py b/mesonbuild/dependencies/base.py
index e375f10..b369780 100644
--- a/mesonbuild/dependencies/base.py
+++ b/mesonbuild/dependencies/base.py
@@ -1057,6 +1057,10 @@ class ExternalProgram:
         r = '<{} {!r} -> {!r}>'
         return r.format(self.__class__.__name__, self.name, self.command)
 
+    def description(self):
+        '''Human friendly description of the command'''
+        return ' '.join(self.command)
+
     @staticmethod
     def from_cross_info(cross_info, name):
         if name not in cross_info.config['binaries']:
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index dba3fc0..9bd21e3 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -480,7 +480,7 @@ class ExternalProgramHolder(InterpreterObject, ObjectHolder):
         return self.held_object.get_path()
 
     def found(self):
-        return self.held_object.found()
+        return isinstance(self.held_object, build.Executable) or self.held_object.found()
 
     def get_command(self):
         return self.held_object.get_command()
@@ -1780,9 +1780,8 @@ class MesonMain(InterpreterObject):
             if not os.path.exists(abspath):
                 raise InterpreterException('Tried to override %s with a file that does not exist.' % name)
             exe = dependencies.ExternalProgram(abspath)
-        if not isinstance(exe, dependencies.ExternalProgram):
-            # FIXME, make this work if the exe is an Executable target.
-            raise InterpreterException('Second argument must be an external program.')
+        if not isinstance(exe, (dependencies.ExternalProgram, build.Executable)):
+            raise InterpreterException('Second argument must be an external program or executable.')
         self.interpreter.add_find_program_override(name, exe)
 
     @noPosargs
@@ -2184,6 +2183,11 @@ external dependencies (including libraries) must go to "dependencies".''')
             'or configure_file(), or a compiler object; not {!r}'
         if isinstance(cmd, ExternalProgramHolder):
             cmd = cmd.held_object
+            if isinstance(cmd, build.Executable):
+                progname = node.args.arguments[0].value
+                msg = 'Program {!r} was overridden with the compiled executable {!r}'\
+                      ' and therefore cannot be used during configuration'
+                raise InterpreterException(msg.format(progname, cmd.description()))
         elif isinstance(cmd, CompilerHolder):
             cmd = cmd.compiler.get_exelist()[0]
             prog = ExternalProgram(cmd, silent=True)
@@ -2758,7 +2762,7 @@ external dependencies (including libraries) must go to "dependencies".''')
                 exe = self.build.find_overrides[name]
                 if not silent:
                     mlog.log('Program', mlog.bold(name), 'found:', mlog.green('YES'),
-                             '(overridden: %s)' % ' '.join(exe.command))
+                             '(overridden: %s)' % exe.description())
                 return ExternalProgramHolder(exe)
         return None