bazel: fix python stub paths

pkgs/development/tools/build-managers/bazel/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, lib, fetchurl, fetchpatch, runCommand, makeWrapper
+{ stdenv, callPackage, lib, fetchurl, fetchpatch, runCommand, makeWrapper
 , jdk, zip, unzip, bash, writeCBin, coreutils
 , which, python, perl, gnused, gnugrep, findutils
 # Apple dependencies
@@ -38,6 +38,11 @@ stdenv.mkDerivation rec {
     platforms = platforms.linux ++ platforms.darwin;
   };
 
+  # additional tests that check bazel’s functionality
+  passthru.tests = {
+    python_bin_path = callPackage ./python-bin-path-test.nix {};
+  };
+
   name = "bazel-${version}";
 
   src = fetchurl {
@@ -47,8 +52,10 @@ stdenv.mkDerivation rec {
 
   sourceRoot = ".";
 
-  patches =
-    lib.optional enableNixHacks ./nix-hacks.patch;
+  patches = [
+    (lib.optional enableNixHacks ./nix-hacks.patch)
+    ./python-stub-path-fix.patch
+    ];
 
   # Bazel expects several utils to be available in Bash even without PATH. Hence this hack.
 
@@ -118,6 +125,10 @@ stdenv.mkDerivation rec {
     '';
 
     genericPatches = ''
+      # Substitute python's stub shebang to plain python path. (see TODO add pr URL)
+      substituteInPlace src/main/java/com/google/devtools/build/lib/bazel/rules/python/python_stub_template.txt\
+          --replace "/usr/bin/env python" "${python}/bin/python" \
+          --replace "NIX_STORE_PYTHON_PATH" "${python}/bin/python" \
       # substituteInPlace is rather slow, so prefilter the files with grep
       grep -rlZ /bin src/main/java/com/google/devtools | while IFS="" read -r -d "" path; do
         # If you add more replacements here, you must change the grep above!
@@ -137,6 +148,7 @@ stdenv.mkDerivation rec {
         --replace '"jvm_opts": JDK9_JVM_OPTS' \
                   '"jvm_opts": JDK8_JVM_OPTS'
 
+
       # add nix environment vars to .bazelrc
       cat >> .bazelrc <<EOF
       build --experimental_distdir=${distDir}

pkgs/development/tools/build-managers/bazel/python-bin-path-test.nix

@@ -0,0 +1,55 @@
+{ stdenv, lib, writeText, runCommandCC, bazel }:
+
+let
+  WORKSPACE = writeText "WORKSPACE" ''
+    workspace(name = "our_workspace")
+  '';
+
+  pythonLib = writeText "lib.py" ''
+    def foo():
+      return 43
+  '';
+
+  pythonBin = writeText "bin.py" ''
+    from lib import foo
+
+    assert foo() == 43
+  '';
+
+  pythonBUILD = writeText "BUILD" ''
+    py_library(
+      name = "lib",
+      srcs = [ "lib.py" ],
+    )
+
+    py_test(
+      name = "bin",
+      srcs = [ "bin.py" ],
+      deps = [ ":lib" ],
+    )
+  '';
+
+  runLocal = name: script: runCommandCC name { preferLocalBuild = true; } script;
+
+  workspaceDir = runLocal "our_workspace" ''
+    mkdir $out
+    cp ${WORKSPACE} $out/WORKSPACE
+    mkdir $out/python
+    cp ${pythonLib} $out/python/lib.py
+    cp ${pythonBin} $out/python/bin.py
+    cp ${pythonBUILD} $out/python/BUILD.bazel
+  '';
+
+  testBazel = runLocal "bazel-test-builtin-rules" ''
+    export HOME=$(mktemp -d)
+    cp -r ${workspaceDir}/* .
+    ${bazel}/bin/bazel --output_base=/tmp/bazel-tests/wd\
+      test \
+        --test_output=errors \
+        --host_javabase='@local_jdk//:jdk' \
+        //...
+
+    touch $out
+  '';
+
+in testBazel

pkgs/development/tools/build-managers/bazel/python-stub-path-fix.patch

@@ -0,0 +1,13 @@
+diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/python_stub_template.txt b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/python_stub_template.txt
+index dac21c9a83..69b11c283f 100644
+--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/python_stub_template.txt
++++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/python_stub_template.txt
+@@ -67,7 +67,7 @@ def FindPythonBinary(module_space):
+     return os.path.join(module_space, PYTHON_BINARY)
+   else:
+     # Case 4: Path has to be looked up in the search path.
+-    return SearchPath(PYTHON_BINARY)
++    return "NIX_STORE_PYTHON_PATH"
+
+ def CreatePythonPathEntries(python_imports, module_space):
+   parts = python_imports.split(':');