From e2e1751a06b1ba79b651417343bb27ee04140d34 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Mon, 3 Aug 2015 15:10:31 -0700
Subject: [PATCH] Fix activating features in dependencies transitively

When activating the feature `foo/bar` you're actually activating both the
feature `foo` and the `bar` feature of the relevant package. Cargo previously
forgot to activate the `foo` feature, and this commit fixes that up.

Closes #1871
---
 src/cargo/core/resolver/mod.rs |  1 +
 tests/test_cargo_features.rs   | 38 ++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/src/cargo/core/resolver/mod.rs b/src/cargo/core/resolver/mod.rs
index 0fe74b8d8..223966a9d 100644
--- a/src/cargo/core/resolver/mod.rs
+++ b/src/cargo/core/resolver/mod.rs
@@ -556,6 +556,7 @@ fn build_features(s: &Summary, method: Method)
         match parts.next() {
             Some(feat) => {
                 let package = feat_or_package;
+                used.insert(package.to_string());
                 deps.entry(package.to_string())
                     .or_insert(Vec::new())
                     .push(feat.to_string());
diff --git a/tests/test_cargo_features.rs b/tests/test_cargo_features.rs
index 33a058f0e..11211087b 100644
--- a/tests/test_cargo_features.rs
+++ b/tests/test_cargo_features.rs
@@ -769,3 +769,41 @@ test!(optional_and_dev_dep {
 {compiling} test v0.1.0 ([..])
 ", compiling = COMPILING)));
 });
+
+test!(activating_feature_activates_dep {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name    = "test"
+            version = "0.1.0"
+            authors = []
+
+            [dependencies]
+            foo = { path = "foo", optional = true }
+
+            [features]
+            a = ["foo/a"]
+        "#)
+        .file("src/lib.rs", "
+            extern crate foo;
+            pub fn bar() {
+                foo::bar();
+            }
+        ")
+        .file("foo/Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.1.0"
+            authors = []
+
+            [features]
+            a = []
+        "#)
+        .file("foo/src/lib.rs", r#"
+            #[cfg(feature = "a")]
+            pub fn bar() {}
+        "#);
+
+    assert_that(p.cargo_process("build").arg("--features").arg("a").arg("-v"),
+                execs().with_status(0));
+});
-- 
2.30.2