Fix NixOS#11 - Add optional dependencies if a feature "<dep name>/fea…

…ture" is enabled

Cargo.nix

@@ -19,6 +19,8 @@ rec {
   #
 
   rootCrate = {
+    packageId = "crate2nix 0.5.0-alpha.0 (path+file:///home/peter/projects/crate2nix)";
+
     # Use this attribute to refer to the derivation building your root crate package.
     # You can override the features with rootCrate.build.override { features = [ "default" "feature1" ... ]; }.
     build = buildRustCrateWithFeatures {
@@ -33,6 +35,7 @@ rec {
   # workspaceMembers."${crateName}".build.override { features = [ "default" "feature1" ... ]; }.
   workspaceMembers = {
     "crate2nix" = {
+      packageId = "crate2nix 0.5.0-alpha.0 (path+file:///home/peter/projects/crate2nix)";
       build = buildRustCrateWithFeatures {
         packageId = "crate2nix 0.5.0-alpha.0 (path+file:///home/peter/projects/crate2nix)";
         features = rootFeatures;
@@ -2597,9 +2600,16 @@ rec {
       (depName: dep:
         builtins.isString dep
         || dep.target or true
-        && (!(dep.optional or false) || builtins.elem depName features))
+        && (!(dep.optional or false) || builtins.any (doesFeatureEnableDependency depName) features))
       dependencies;
 
+  /* Returns whether the given feature should enable the given dependency. */
+  doesFeatureEnableDependency = depName: feature:
+    let prefix = "${depName}/";
+        len = builtins.stringLength prefix;
+        startsWithPrefix = builtins.substring 0 len feature == prefix;
+    in feature == depName || startsWithPrefix;
+
   /* Returns the expanded features for the given inputFeatures by applying the rules in featureMap.
 
      featureMap is an attribute set which maps feature names to lists of further feature names to enable in case this

sample_projects/numtest/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "numtest"
+version = "0.1.0"
+authors = ["Peter Kolloch <info@eigenvalue.net>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+num = "0.2.0"

sample_projects/numtest/crate-hashes.json

@@ -0,0 +1,10 @@
+{
+  "autocfg 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)": "1f3bj604fyr4xh08r357hs3hpdzapiqgccvmj1jpi953ffqrp09a",
+  "num 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)": "0kkql31mc46lghl2qyirk5vl6l0ij24cb5q9d23zm7bkfm05rmzx",
+  "num-bigint 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)": "0alza0afrwvhiilqvjazkxv94sir14jqfi50cpv40rgjl1rk7xf6",
+  "num-complex 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)": "1l8gwn4cqhx77wzhzslwxhryrr5h4vsv19ys8wr5xb1g332805m9",
+  "num-integer 0.1.41 (registry+https://github.com/rust-lang/crates.io-index)": "1y45nh9xlp2dra9svb1wfsy65fysm3k1w4m8jynywccq645yixid",
+  "num-iter 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)": "003j2hysdrkia435vxn38s1qs8cllrgk04l4aapb8hd0wci109mj",
+  "num-rational 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)": "0igg7jnhsxffy3qdvq30pv5h58a9a20h43s4qpxviyzi5zmzqsx2",
+  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)": "1mnlmy35n734n9xlq0qkfbgzz33x09a1s4rfj30p1976p09b862v"
+}

sample_projects/numtest/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello from numtest, world!");
+}

templates/build.nix.tera

@@ -22,6 +22,8 @@ rec {
 
   {% if root_package_id -%}
   rootCrate = {
+    packageId = {{root_package_id}};
+
     # Use this attribute to refer to the derivation building your root crate package.
     # You can override the features with rootCrate.build.override { features = [ "default" "feature1" ... ]; }.
     build = buildRustCrateWithFeatures {
@@ -39,6 +41,7 @@ rec {
   workspaceMembers = {
   {%- for name, pkg_id in workspace_members %}
     {{name}} = {
+      packageId = {{pkg_id}};
       build = buildRustCrateWithFeatures {
         packageId = {{pkg_id}};
         features = rootFeatures;

templates/nix/crate2nix/default.nix

@@ -183,9 +183,16 @@ rec {
       (depName: dep:
         builtins.isString dep
         || dep.target or true
-        && (!(dep.optional or false) || builtins.elem depName features))
+        && (!(dep.optional or false) || builtins.any (doesFeatureEnableDependency depName) features))
       dependencies;
 
+  /* Returns whether the given feature should enable the given dependency. */
+  doesFeatureEnableDependency = depName: feature:
+    let prefix = "${depName}/";
+        len = builtins.stringLength prefix;
+        startsWithPrefix = builtins.substring 0 len feature == prefix;
+    in feature == depName || startsWithPrefix;
+
   /* Returns the expanded features for the given inputFeatures by applying the rules in featureMap.
 
      featureMap is an attribute set which maps feature names to lists of further feature names to enable in case this

templates/nix/crate2nix/tests/packageFeatures.nix

@@ -43,12 +43,68 @@ let crateConfigs = {
         crateName = "id3";
         features = {};
       };
+
+      "pkg_numtest" = {
+        crateName = "numtest";
+        dependencies = {
+            "num" = "pkg_num";
+        };
+      };
+
+      "pkg_num_bigint" = {
+        crateName = "num-bigint";
+      };
+
+      "pkg_num" = {
+        crateName = "num";
+        dependencies = {
+            "num-bigint" = {
+                packageId = "pkg_num_bigint";
+                usesDefaultFeatures = false;
+                optional = true;
+            };
+        };
+        features = {
+            "default" = [ "std" ];
+            "std" = [ "num-bigint/std" ];
+        };
+      };
     };
     packageFeatures = packageId: features: {
         list = crate2nix.listOfPackageFeatures {inherit crateConfigs packageId features;};
         merged = crate2nix.mergePackageFeatures {inherit crateConfigs packageId features;};
       };
 in lib.runTests {
+  testNumDependencies = {
+    expr = packageFeatures "pkg_num" ["default"];
+    expected = {
+      list = [
+        { packageId = "pkg_num"; features = ["default" "num-bigint/std" "std"]; }
+        { packageId = "pkg_num_bigint"; features = ["std"]; }
+      ];
+      merged = {
+        "pkg_num" = ["default" "num-bigint/std" "std"];
+        "pkg_num_bigint" = ["std"];
+      };
+    };
+  };
+
+  testNumTestDependencies = {
+    expr = packageFeatures "pkg_numtest" ["default"];
+    expected = {
+      list = [
+        { packageId = "pkg_numtest"; features = ["default"]; }
+        { packageId = "pkg_num"; features = ["default" "num-bigint/std" "std"]; }
+        { packageId = "pkg_num_bigint"; features = ["std"]; }
+      ];
+      merged = {
+        "pkg_numtest" = ["default"];
+        "pkg_num" = ["default" "num-bigint/std" "std"];
+        "pkg_num_bigint" = ["std"];
+      };
+    };
+  };
+
   testTerminalPackageDependency = {
     expr = packageFeatures "pkg_id1" [];
     expected = {

tests/sample_projects.rs

@@ -103,6 +103,19 @@ fn build_and_run_with_problematic_crates() {
     assert_eq!("Hello, with_problematic_crates!\n", &output);
 }
 
+#[test]
+fn build_and_run_numtest() {
+    let output = build_and_run(
+        "sample_projects/numtest/Cargo.toml",
+        "sample_projects/numtest",
+        "rootCrate",
+        "numtest",
+        &["default"],
+    );
+
+    assert_eq!("Hello from numtest, world!\n", &output);
+}
+
 #[test]
 fn build_and_run_bin_with_lib_git_dep() {
     let output = build_and_run(