It’s possible to build optional dependencies not listed in Cargo.lock #3629
Description
Test case: (run in a temporary directory)
cargo new a
cd a
echo 'b = {path = "b"}' >> Cargo.toml
cargo new b
cd b
echo 'c = {path = "c", optional = true}' >> Cargo.toml
cargo new c
cd c
echo 'd = {path = "d"}' >> Cargo.toml
cargo new d
cd ..
cd ..
cargo build --features b/c --verbose
cat Cargo.lock
cd ..
rm -rf aOutput in cargo 0.17.0-nightly (67e4ef1 2017-01-25)
Created library `a` project
Created library `b` project
Created library `c` project
Created library `d` project
Compiling d v0.1.0 (file:///tmp/lol/a/b/c/d)
Running `rustc --crate-name d b/c/d/src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=d1f001e6c4277757 -C extra-filename=-d1f001e6c4277757 --out-dir /tmp/lol/a/target/debug/deps -L dependency=/tmp/lol/a/target/debug/deps`
Compiling c v0.1.0 (file:///tmp/lol/a/b/c)
Running `rustc --crate-name c b/c/src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=d3fb71d0c424d062 -C extra-filename=-d3fb71d0c424d062 --out-dir /tmp/lol/a/target/debug/deps -L dependency=/tmp/lol/a/target/debug/deps --extern d=/tmp/lol/a/target/debug/deps/libd-d1f001e6c4277757.rlib`
Compiling b v0.1.0 (file:///tmp/lol/a/b)
Running `rustc --crate-name b b/src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 --cfg 'feature="c"' -C metadata=bf9fdaf735940263 -C extra-filename=-bf9fdaf735940263 --out-dir /tmp/lol/a/target/debug/deps -L dependency=/tmp/lol/a/target/debug/deps --extern c=/tmp/lol/a/target/debug/deps/libc-d3fb71d0c424d062.rlib`
Compiling a v0.1.0 (file:///tmp/lol/a)
Running `rustc --crate-name a src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 --cfg 'feature="b"' -C metadata=50db5a511b950de6 -C extra-filename=-50db5a511b950de6 --out-dir /tmp/lol/a/target/debug/deps -L dependency=/tmp/lol/a/target/debug/deps --extern b=/tmp/lol/a/target/debug/deps/libb-bf9fdaf735940263.rlib`
Finished dev [unoptimized + debuginfo] target(s) in 2.22 secs
[root]
name = "a"
version = "0.1.0"
dependencies = [
"b 0.1.0",
]
[[package]]
name = "b"
version = "0.1.0"Crates c and d were compiled and used, but are not listed in Cargo.lock.