Fix for finding dependency version in lockfile v2

With lockfile v2 a version is not required for dependencies if the lock
file only contains a single entry for a specified crate.  However, without
a version present, at a later stage, a dependant crate will not be found
in the metadata cache which causes the dependency to be ignored completely.
This commit tries to infer the version of dependant crates when the
version specifier is missing from the contents of the lockfile.

src/bindgen/cargo/cargo.rs

@@ -135,6 +135,26 @@ impl Cargo {
             .map(|dep| {
                 let (dep_name, dep_version) = parse_dep_string(dep);
 
+                // If a version was not specified find the only package with the name of the dependency
+                let dep_version = dep_version.or_else(|| {
+                    let mut versions = self.metadata.packages.iter().filter_map(|package| {
+                        if package.name_and_version.name != dep_name {
+                            return None;
+                        }
+                        package.name_and_version.version.as_ref().map(|v| v.as_str())
+                    });
+
+                    // If the iterator contains more items, meaning multiple versions of the same
+                    // package are present, warn! amd abort.
+                    let version = versions.next();
+                    if versions.next().is_none() {
+                        version
+                    } else {
+                        warn!("when looking for a version for package {}, multiple versions where found", dep_name);
+                        None
+                    }
+                });
+
                 // Try to find the cfgs in the Cargo.toml
                 let cfg = self
                     .metadata

tests/expectations/both/dep_v2.c

@@ -0,0 +1,11 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef struct dep_struct {
+  uint32_t x;
+  double y;
+} dep_struct;
+
+uint32_t get_x(const dep_struct *dep_struct);

tests/expectations/both/dep_v2.compat.c

@@ -0,0 +1,19 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef struct dep_struct {
+  uint32_t x;
+  double y;
+} dep_struct;
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+uint32_t get_x(const dep_struct *dep_struct);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus

tests/expectations/dep_v2.c

@@ -0,0 +1,11 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef struct {
+  uint32_t x;
+  double y;
+} dep_struct;
+
+uint32_t get_x(const dep_struct *dep_struct);

tests/expectations/dep_v2.compat.c

@@ -0,0 +1,19 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef struct {
+  uint32_t x;
+  double y;
+} dep_struct;
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+uint32_t get_x(const dep_struct *dep_struct);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus

tests/expectations/dep_v2.cpp

@@ -0,0 +1,15 @@
+#include <cstdarg>
+#include <cstdint>
+#include <cstdlib>
+#include <new>
+
+struct dep_struct {
+  uint32_t x;
+  double y;
+};
+
+extern "C" {
+
+uint32_t get_x(const dep_struct *dep_struct);
+
+} // extern "C"

tests/expectations/tag/dep_v2.c

@@ -0,0 +1,11 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+struct dep_struct {
+  uint32_t x;
+  double y;
+};
+
+uint32_t get_x(const struct dep_struct *dep_struct);

tests/expectations/tag/dep_v2.compat.c

@@ -0,0 +1,19 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+struct dep_struct {
+  uint32_t x;
+  double y;
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+uint32_t get_x(const struct dep_struct *dep_struct);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus

tests/rust/dep_v2/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "expand-dep"
+version = "0.1.0"
+authors = ["cbindgen"]
+edition = "2018"
+
+[dependencies]
+dep = { path = "dep" }

tests/rust/dep_v2/cbindgen.toml

@@ -0,0 +1,3 @@
+[parse]
+parse_deps = true
+include = ["dep"]

tests/rust/dep_v2/dep/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "dep"
+version = "0.1.0"
+authors = ["cbindgen"]
+edition = "2018"
+
+[dependencies]

tests/rust/dep_v2/dep/src/lib.rs

@@ -0,0 +1,5 @@
+#[repr(C)]
+pub struct dep_struct {
+    pub x: u32,
+    pub y: f64,
+}

tests/rust/dep_v2/src/lib.rs

@@ -0,0 +1,6 @@
+use dep::dep_struct;
+
+#[no_mangle]
+pub unsafe extern "C" fn get_x(dep_struct: *const dep_struct) -> u32 {
+    dep_struct.read().x
+}