wrap: Implement special wrap modes for use by packagers

Special wrap modes:
  nofallback: Don't download wraps for dependency() fallbacks
  nodownload: Don't download wraps for all subproject() calls

Subprojects are used for two purposes:
1. To download and build dependencies by using .wrap files if they
   are not provided by the system. This is usually expressed via
   dependency(..., fallback: ...).
2. To download and build 'copylibs' which are meant to be used by
   copying into your project. This is always done with an explicit
   subproject() call.

--wrap-mode=nofallback will never do (1)
--wrap-mode=nodownload will do neither (1) nor (2)

If you are building from a release tarball, you should be able to
safely use 'nodownload' since upstream is expected to ship all
required sources with the tarball.

If you are building from a git repository, you will want to use
'nofallback' so that any 'copylib' wraps will be download as
subprojects.

Note that these options do not affect subprojects that are git
submodules since those are only usable in git repositories, and you
almost always want to download them.

1 files changed, 31 insertions, 0 deletions

diff --git a/mesonbuild/wrap/__init__.py b/mesonbuild/wrap/__init__.py
index e69de29..019634c 100644
--- a/mesonbuild/wrap/__init__.py
+++ b/mesonbuild/wrap/__init__.py
@@ -0,0 +1,31 @@
+from enum import Enum
+
+# Used for the --wrap-mode command-line argument
+#
+# Special wrap modes:
+#   nofallback: Don't download wraps for dependency() fallbacks
+#   nodownload: Don't download wraps for all subproject() calls
+#
+# subprojects are used for two purposes:
+# 1. To download and build dependencies by using .wrap
+#    files if they are not provided by the system. This is
+#    usually expressed via dependency(..., fallback: ...).
+# 2. To download and build 'copylibs' which are meant to be
+#    used by copying into your project. This is always done
+#    with an explicit subproject() call.
+#
+# --wrap-mode=nofallback will never do (1)
+# --wrap-mode=nodownload will do neither (1) nor (2)
+#
+# If you are building from a release tarball, you should be
+# able to safely use 'nodownload' since upstream is
+# expected to ship all required sources with the tarball.
+#
+# If you are building from a git repository, you will want
+# to use 'nofallback' so that any 'copylib' wraps will be
+# download as subprojects.
+#
+# Note that these options do not affect subprojects that
+# are git submodules since those are only usable in git
+# repositories, and you almost always want to download them.
+WrapMode = Enum('WrapMode', 'default nofallback nodownload')