mkDummySrc: rework to only stub bins if they actually exist

CHANGELOG.md

@@ -9,6 +9,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Changed
 * **Breaking**: dropped compatibility for Nix versions below 2.24.10
 * **Breaking**: dropped compatibility for nixpkgs-23.11
+* `mkDummySrc` has been reworked to match cargo's `autobin` detection logic,
+  meaning that only real binary targets defined by the project will be dummified
+  if they exist (no more injecting `src/bin/crane-dummy-*`). This does mean that
+  adding a new bin target definition will invalidate caches and require
+  rebuilding all dependencies once more. (If this is a frequent enough
+  occurrence for your project to cause headaches, please open an issue!)
 
 ## [0.19.4] - 2024-11-30
 

checks/default.nix

@@ -469,7 +469,7 @@ in
     lib.optionalAttrs x64Linux (noStdLib.buildPackage {
       src = noStdLib.cleanCargoSource ./no_std;
       CARGO_BUILD_TARGET = "x86_64-unknown-none";
-      cargoCheckExtraArgs = "--lib --bins --examples";
+      cargoCheckExtraArgs = "--bins --examples";
       doCheck = false;
     });
 
@@ -485,7 +485,7 @@ in
     lib.optionalAttrs x64Linux (bindepsLib.buildPackage {
       src = bindepsLib.cleanCargoSource ./bindeps;
       CARGO_BUILD_TARGET = "x86_64-unknown-none";
-      cargoCheckExtraArgs = "--lib --bins --examples";
+      cargoCheckExtraArgs = "--bins --examples";
       doCheck = false;
     });
 
@@ -808,6 +808,13 @@ in
     pname = "workspace-root";
   };
 
+  # https://github.com/ipetkov/crane/issues/268
+  workspaceRootSpecificBin = myLib.buildPackage {
+    src = myLib.cleanCargoSource ./workspace-root;
+    pname = "workspace-root";
+    cargoExtraArgs = "--bin print";
+  };
+
   workspaceGit = myLib.buildPackage {
     src = myLib.cleanCargoSource ./workspace-git;
   };

docs/API.md

@@ -1268,6 +1268,9 @@ build caches. More specifically:
   - Any changes to the `[package]` definition such as name and version
   - Any changes to the name or path of any target (such as benches, bins,
     examples, libs, or tests)
+  - Any removal or new definition of a `[[bin]]` target, or, any removal or new
+    definition of a file under `src/bin` when `autolib` is enabled in the
+    `Cargo.toml` file (this setting is `true` by default)
 
 #### Required attributes
 * `src`: a source directory which should be turned into a "dummy" form

lib/mkDummySrc.nix

@@ -19,7 +19,6 @@ let
   inherit (builtins)
     dirOf
     concatStringsSep
-    hasAttr
     match
     storeDir;
 
@@ -162,6 +161,9 @@ let
         cargoTomlDest = builtins.unsafeDiscardStringContext (removePrefix cargoTomlsBase (toString p));
         parentDir = "$out/${dirOf cargoTomlDest}";
 
+        # NB: do not use string interpolation or toString or else the path checks won't work
+        shallowJoinPath = rest: p + "/../${rest}";
+
         # Override the cleaned Cargo.toml with a build script which points to our dummy
         # source. We need a build script present to cache build-dependencies, which can be
         # achieved by dropping a build.rs file in the source directory. Except that is the most
@@ -187,10 +189,44 @@ let
           else
             cleanedCargoToml;
 
-        safeStubLib =
-          if hasAttr "lib" trimmedCargoToml
-          then cpDummy parentDir (trimmedCargoToml.lib.path or "src/lib.rs")
-          else "";
+
+        hasDir = root: sub: root.${sub} or "" == "directory";
+        hasFile = root: sub: root.${sub} or "" == "regular";
+
+        crateRoot = builtins.readDir (shallowJoinPath ".");
+        srcDir = lib.optionalAttrs (hasDir crateRoot "src") (builtins.readDir (shallowJoinPath "src"));
+        hasLibrs = (trimmedCargoToml.package.autolib or true) && hasFile srcDir "lib.rs";
+        autobins = trimmedCargoToml.package.autobins or true;
+        hasMainrs = autobins && hasFile srcDir "main.rs";
+        srcBinDir = lib.optionalAttrs (autobins && hasDir srcDir "bin") (builtins.readDir (shallowJoinPath "src/bin"));
+
+        # NB: sort the result here to be as deterministic as possible and avoid rebuilds if
+        # directory listings happen to change their order
+        discoveredBins = concatStringsSep " " (lib.sortOn (x: x) (lib.filter (p: p != null)
+          (lib.flip map (lib.attrsToList srcBinDir) ({ name, value }:
+            let
+              short = "src/bin/${name}";
+              long = "${short}/main.rs";
+            in
+            lib.escapeShellArg (
+              if value == "regular"
+              then short
+              else if value == "directory" && builtins.pathExists (shallowJoinPath long)
+              then long
+              else null
+            )
+          ))
+        ));
+
+        stubBins = ''(
+          cd ${parentDir}
+          echo ${discoveredBins} | xargs --no-run-if-empty -n1 dirname | sort -u | xargs --no-run-if-empty mkdir -p
+          echo ${discoveredBins} | xargs --no-run-if-empty -n1 cp -f ${dummyrs}
+        )'';
+
+        safeStubLib = lib.optionalString
+          (trimmedCargoToml ? lib || hasLibrs)
+          (cpDummy parentDir (trimmedCargoToml.lib.path or "src/lib.rs"));
 
         safeStubList = attr: defaultPath:
           let
@@ -205,8 +241,8 @@ let
         cp ${writeTOML "Cargo.toml" trimmedCargoToml} $out/${cargoTomlDest}
       '' + optionalString (trimmedCargoToml ? package) ''
         # To build regular and dev dependencies (cargo build + cargo test)
-        ${cpDummy parentDir "src/lib.rs"}
-        ${cpDummy parentDir "src/bin/crane-dummy-${trimmedCargoToml.package.name or "no-name"}/main.rs"}
+        ${lib.optionalString hasMainrs (cpDummy parentDir "src/main.rs")}
+        ${stubBins}
 
         # Stub all other targets in case they have particular feature combinations
         ${safeStubLib}

lib/setupHooks/inheritCargoArtifactsHook.sh

@@ -74,10 +74,22 @@ inheritCargoArtifacts() {
         --executability \
         --exclude 'deps/*.rlib' \
         --exclude 'deps/*.rmeta' \
-        --exclude '.cargo-lock' \
         "${preparedArtifacts}/" \
         "${cargoTargetDir}/"
 
+      # NB: cargo also doesn't like it if `.cargo-lock` files remain with a
+      # timestamp in the distant past so we need to delete them here
+      # NB: `.cargo-lock` files tend to appear in "top level" profile artifact directories.
+      # Those directories usually contain a `*.d` file for each binary target, but these are NOT
+      # content addressed, so we will want to copy them directly so they become writable in place
+      find "${cargoTargetDir}" -name '.cargo-lock' -delete \
+       -execdir bash -c '
+         for f in *.d; do
+           cp --preserve=timestamps --no-preserve=ownership --remove-destination "$(readlink "${f}")" "${f}"
+           chmod u+w "${f}"
+         done
+       ' \;
+
       local linkCandidates=$(mktemp linkCandidatesXXXX.txt)
       find "${preparedArtifacts}" \
         '(' -path '*/deps/*.rlib' -or -path '*/deps/*.rmeta' ')' \