buildRustCrate: add support for renaming crates

Before this change, buildRustCrate always called rustc with

--extern libName=[...]libName[...]

However, Cargo permits using a different name under which a dependency
is known to a crate. For example, rand 0.7.0 uses:

[dependencies]
getrandom_package = { version = "0.1.1", package = "getrandom", optional = true }

Which introduces the getrandom dependency such that it is known as
getrandom_package to the rand crate. In this case, the correct extern
flag is of the form

--extern getrandom_package=[...]getrandom[...]

which is currently not supported. In order to support such cases, this
change introduces a crateRenames argument to buildRustCrate. This
argument is an attribute set of dependencies that should be renamed. In
this case, crateRenames would be:

{
  "getrandom" = "getrandom_package";
}

The extern options are then built such that if the libName occurs as
an attribute in this set, it value will be used as the local
name. Otherwise libName will be used as before.

pkgs/build-support/rust/build-rust-crate/build-crate.nix

@@ -1,13 +1,13 @@
 { lib, stdenv, echo_build_heading, noisily, makeDeps }:
 { crateName,
   dependencies,
-  crateFeatures, libName, release, libPath,
+  crateFeatures, crateRenames, libName, release, libPath,
   crateType, metadata, crateBin, hasCrateBin,
   extraRustcOpts, verbose, colors }:
 
   let
 
-    deps = makeDeps dependencies;
+    deps = makeDeps dependencies crateRenames;
     rustcOpts =
       lib.lists.foldl' (opts: opt: opts + " " + opt)
         (if release then "-C opt-level=3" else "-C debuginfo=2")

pkgs/build-support/rust/build-rust-crate/configure-crate.nix

@@ -9,6 +9,7 @@
 , crateHomepage
 , crateFeatures
 , crateName
+, crateRenames
 , crateVersion
 , extraLinkFlags
 , extraRustcOpts
@@ -24,7 +25,7 @@ let version_ = lib.splitString "-" crateVersion;
     rustcOpts = lib.lists.foldl' (opts: opt: opts + " " + opt)
         (if release then "-C opt-level=3" else "-C debuginfo=2")
         (["-C codegen-units=$NIX_BUILD_CORES"] ++ extraRustcOpts);
-    buildDeps = makeDeps buildDependencies;
+    buildDeps = makeDeps buildDependencies crateRenames;
     authors = lib.concatStringsSep ":" crateAuthors;
     optLevel = if release then 3 else 0;
     completeDepsDir = lib.concatStringsSep " " completeDeps;

pkgs/build-support/rust/build-rust-crate/default.nix

@@ -13,13 +13,18 @@ let
       then "macos"
       else stdenv.hostPlatform.parsed.kernel.name;
 
-    makeDeps = dependencies:
+    makeDeps = dependencies: crateRenames:
       (lib.concatMapStringsSep " " (dep:
-        let extern = lib.strings.replaceStrings ["-"] ["_"] dep.libName; in
-        (if lib.lists.any (x: x == "lib") dep.crateType then
-           " --extern ${extern}=${dep.out}/lib/lib${extern}-${dep.metadata}.rlib"
+        let
+          extern = lib.strings.replaceStrings ["-"] ["_"] dep.libName;
+          name = if builtins.hasAttr dep.crateName crateRenames then
+            lib.strings.replaceStrings ["-"] ["_"] crateRenames.${dep.crateName}
+          else
+            extern;
+        in (if lib.lists.any (x: x == "lib") dep.crateType then
+           " --extern ${name}=${dep.out}/lib/lib${extern}-${dep.metadata}.rlib"
          else
-           " --extern ${extern}=${dep.out}/lib/lib${extern}-${dep.metadata}${stdenv.hostPlatform.extensions.sharedLibrary}")
+           " --extern ${name}=${dep.out}/lib/lib${extern}-${dep.metadata}${stdenv.hostPlatform.extensions.sharedLibrary}")
       ) dependencies);
 
     echo_build_heading = colors: ''
@@ -60,7 +65,7 @@ let
     in
 
 crate_: lib.makeOverridable ({ rust, release, verbose, features, buildInputs, crateOverrides,
-  dependencies, buildDependencies,
+  dependencies, buildDependencies, crateRenames,
   extraRustcOpts,
   preUnpack, postUnpack, prePatch, patches, postPatch,
   preConfigure, postConfigure, preBuild, postBuild, preInstall, postInstall }:
@@ -70,7 +75,7 @@ let crate = crate_ // (lib.attrByPath [ crate_.crateName ] (attr: {}) crateOverr
     buildDependencies_ = buildDependencies;
     processedAttrs = [
       "src" "buildInputs" "crateBin" "crateLib" "libName" "libPath"
-      "buildDependencies" "dependencies" "features"
+      "buildDependencies" "dependencies" "features" "crateRenames"
       "crateName" "version" "build" "authors" "colors" "edition"
     ];
     extraDerivationAttrs = lib.filterAttrs (n: v: ! lib.elem n processedAttrs) crate;
@@ -143,13 +148,13 @@ stdenv.mkDerivation (rec {
 
     configurePhase = configureCrate {
       inherit crateName buildDependencies completeDeps completeBuildDeps crateDescription
-              crateFeatures libName build workspace_member release libPath crateVersion
+              crateFeatures crateRenames libName build workspace_member release libPath crateVersion
               extraLinkFlags extraRustcOpts
               crateAuthors crateHomepage verbose colors target_os;
     };
     buildPhase = buildCrate {
       inherit crateName dependencies
-              crateFeatures libName release libPath crateType
+              crateFeatures crateRenames libName release libPath crateType
               metadata crateBin hasCrateBin verbose colors
               extraRustcOpts;
     };
@@ -177,4 +182,5 @@ stdenv.mkDerivation (rec {
   postInstall = crate_.postInstall or "";
   dependencies = crate_.dependencies or [];
   buildDependencies = crate_.buildDependencies or [];
+  crateRenames = crate_.crateRenames or {};
 }

pkgs/build-support/rust/build-rust-crate/test/default.nix

@@ -22,6 +22,13 @@ let
     }
   '';
 
+  mkBinExtern = name: extern: mkFile name ''
+    extern crate ${extern};
+    fn main() {
+      assert_eq!(${extern}::test(), 23);
+    }
+  '';
+
   mkLib = name: mkFile name "pub fn test() -> i32 { return 23; }";
 
   mkTest = crateArgs: let
@@ -34,12 +41,7 @@ let
     libTestBinary = if !isLib then null else mkCrate {
       crateName = "run-test-${crateName}";
       dependencies = [ crate ];
-      src = mkFile "src/main.rs" ''
-        extern crate ${libName};
-        fn main() {
-          assert_eq!(${libName}::test(), 23);
-        }
-      '';
+      src = mkBinExtern "src/main.rs" libName;
     };
 
     in runCommand "run-buildRustCrate-${crateName}-test" {
@@ -71,6 +73,18 @@ let
       };
       crateBinNoPath3 =  { crateBin = [{ name = "my-binary5"; }]; src = mkBin "src/bin/main.rs"; };
       crateBinNoPath4 =  { crateBin = [{ name = "my-binary6"; }]; src = mkBin "src/main.rs";};
+      crateBinRename1 = {
+        crateBin = [{ name = "my-binary-rename1"; }];
+        src = mkBinExtern "src/main.rs" "foo_renamed";
+        dependencies = [ (mkCrate { crateName = "foo"; src = mkLib "src/lib.rs"; }) ];
+        crateRenames = { "foo" = "foo_renamed"; };
+      };
+      crateBinRename2 = {
+        crateBin = [{ name = "my-binary-rename2"; }];
+        src = mkBinExtern "src/main.rs" "foo_renamed";
+        dependencies = [ (mkCrate { crateName = "foo"; libName = "foolib"; src = mkLib "src/lib.rs"; }) ];
+        crateRenames = { "foo" = "foo_renamed"; };
+      };
     };
     brotliCrates = (callPackage ./brotli-crates.nix {});
   in lib.mapAttrs (key: value: mkTest (value // lib.optionalAttrs (!value?crateName) { crateName = key; })) cases // {