Add partial_dependency method to dependencies

This adds a new method, partial_dependency to all dependencies. These
sub dependencies are copies of the original dependency, but with one or
more of the attributes replaced with an empty list. This allows creating
a sub dependency that has only cflags or drops link_arguments, for
example.

1 files changed, 25 insertions, 0 deletions

diff --git a/docs/markdown/snippets/partial-dependencies.md b/docs/markdown/snippets/partial-dependencies.md
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+## Added new partial_dependency method to dependencies and libraries
+
+It is now possible to use only part of a dependency in a target. This allows,
+for example, to only use headers with convenience libraries to avoid linking
+to the same library multiple times.
+
+```meson
+
+dep = dependency('xcb')
+
+helper = static_library(
+  'helper',
+  ['helper1.c', 'helper2.c'],
+  dependencies : dep.partial_dependency(includes : true),
+]
+
+final = shared_library(
+  'final',
+  ['final.c'],
+  dependencyes : dep,
+)
+```
+
+A partial dependency will have the same name version as the full dependency it
+is derived from, as well as any values requested.