From 98e71e1e65ed2992c06dfa41169a73f0b44df2cf Mon Sep 17 00:00:00 2001
From: Nirbheek Chauhan <nirbheek@centricular.com>
Date: Sat, 25 Mar 2017 01:59:24 +0530
Subject: [PATCH] Allow not-required not-found dependencies in subprojects

Closes https://github.com/mesonbuild/meson/issues/1474
---
 mesonbuild/interpreter.py                     | 10 ++++++++--
 test cases/common/95 dep fallback/meson.build |  4 ++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index cd5db62bd..4ee04854b 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -1938,8 +1938,14 @@ class Interpreter(InterpreterBase):
         try:
             dep = self.subprojects[dirname].get_variable_method([varname], {})
         except KeyError:
-            raise InvalidCode('Fallback variable {!r} in the subproject '
-                              '{!r} does not exist'.format(varname, dirname))
+            if kwargs.get('required', True):
+                m = 'Fallback variable {!r} in the subproject {!r} does not exist'
+                raise DependencyException(m.format(varname, dirname))
+            # If the dependency is not required, don't raise an exception
+            mlog.log('Also couldn\'t find the dependency', mlog.bold(name),
+                     'in the fallback subproject',
+                     mlog.bold(os.path.join(self.subproject_dir, dirname)))
+            return None
         if not isinstance(dep, DependencyHolder):
             raise InvalidCode('Fallback variable {!r} in the subproject {!r} is '
                               'not a dependency object.'.format(varname, dirname))
diff --git a/test cases/common/95 dep fallback/meson.build b/test cases/common/95 dep fallback/meson.build
index 9358d296e..a96520e21 100644
--- a/test cases/common/95 dep fallback/meson.build	
+++ b/test cases/common/95 dep fallback/meson.build	
@@ -5,7 +5,11 @@ bob = dependency('boblib', fallback : ['boblib', 'bob_dep'], required: false,
 if not bob.found()
     error('Bob is actually needed')
 endif
+# boblib subproject exists, but sita_dep doesn't exist
+sita = dependency('sitalib', fallback : ['boblib', 'sita_dep'], required: false)
+# jimmylib subproject doesn't exist
 jimmy = dependency('jimmylib', fallback : ['jimmylib', 'jimmy_dep'], required: false)
+# dummylib subproject fails to configure
 dummy = dependency('dummylib', fallback : ['dummylib', 'dummy_dep'], required: false)
 
 gensrc_py = find_program('gensrc.py')