Avoid calling go_path rule in source mode

extras/gomock.bzl

@@ -19,33 +19,49 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
-load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_context", "go_path")
-load("@io_bazel_rules_go//go/private:providers.bzl", "GoLibrary", "GoPath")
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_context")
+load("@io_bazel_rules_go//go/private:providers.bzl", "GoLibrary")
+load("@bazel_skylib//lib:paths.bzl", "paths")
 
 _MOCKGEN_TOOL = "@com_github_golang_mock//mockgen"
 _MOCKGEN_MODEL_LIB = "@com_github_golang_mock//mockgen/model:go_default_library"
 
 def _gomock_source_impl(ctx):
     go_ctx = go_context(ctx)
-    gopath = "$(pwd)/" + ctx.bin_dir.path + "/" + ctx.attr.gopath_dep[GoPath].gopath
 
+    # create GOPATH and copy source into GOPATH
+    source_relative_path = paths.join("src", ctx.attr.library[GoLibrary].importmap, ctx.file.source.basename)
+    source = ctx.actions.declare_file(paths.join("gopath", source_relative_path))
+    # trim the relative path of source to get GOPATH
+    gopath = source.path[:-len(source_relative_path)]
+    ctx.actions.run_shell(
+        outputs=[source],
+        inputs=[ctx.file.source],
+        command = "mkdir -p {0} && cp -L {1} {0}".format(source.dirname, ctx.file.source.path),
+    )
     # passed in source needs to be in gopath to not trigger module mode
-    args = ["-source", gopath + "/src/" + ctx.attr.library[GoLibrary].importmap + "/" + ctx.file.source.basename]
+    args = ["-source", source.path]
 
     args, needed_files = _handle_shared_args(ctx, args)
 
     if len(ctx.attr.aux_files) > 0:
         aux_files = []
-        for pkg, files in ctx.attr.aux_files.items():
-            for f in files:
-                mapped_f = gopath + "/src/" + ctx.attr.library[GoLibrary].importmap + "/" + f
-                aux_files.append("{0}={1}".format(pkg, mapped_f))
+        for target, pkg in ctx.attr.aux_files.items():
+            f = target.files.to_list()[0]
+            aux = ctx.actions.declare_file(paths.join(gopath, "src", pkg, f.basename))
+            ctx.actions.run_shell(
+                outputs=[aux],
+                inputs=[f],
+                command = "mkdir -p {0} && cp -L {1} {0}".format(aux.dirname, f.path)
+            )
+            aux_files.append("{0}={1}".format(pkg, aux.path))
+            needed_files.append(f)
         args += ["-aux_files", ",".join(aux_files)]
 
     inputs = (
-        ctx.attr.gopath_dep.files.to_list() + needed_files +
+        needed_files +
         go_ctx.sdk.headers + go_ctx.sdk.srcs + go_ctx.sdk.tools
-    ) + [ctx.file.source]
+    ) + [source]
 
     # We can use the go binary from the stdlib for most of the environment
     # variables, but our GOPATH is specific to the library target we were given.
@@ -57,22 +73,18 @@ def _gomock_source_impl(ctx):
             go_ctx.go,
         ],
         command = """
-           source <($PWD/{godir}/go env) &&
-           export PATH=$GOROOT/bin:$PWD/{godir}:$PATH &&
-           export GOPATH={gopath} &&
-           mkdir -p .gocache &&
-           export GOCACHE=$PWD/.gocache &&
-           {cmd} {args} > {out}
+            export GOPATH=$(pwd)/{gopath} &&
+            {cmd} {args} > {out}
         """.format(
-            godir = go_ctx.go.path[:-1 - len(go_ctx.go.basename)],
             gopath = gopath,
             cmd = "$(pwd)/" + ctx.file.mockgen_tool.path,
             args = " ".join(args),
             out = ctx.outputs.out.path,
             mnemonic = "GoMockSourceGen",
         ),
         env = {
-            "GO111MODULE": "off",  # explicitly relying on passed in go_path to not download modules while doing codegen
+            # GOCACHE is required starting in Go 1.12
+            "GOCACHE": "./.gocache",
         },
     )
 
@@ -98,9 +110,10 @@ _gomock_source = rule(
             doc = "Ignored. If `source` is not set, this would be the list of Go interfaces to generate mocks for.",
             mandatory = True,
         ),
-        "aux_files": attr.string_list_dict(
+        "aux_files": attr.label_keyed_string_dict(
             default = {},
-            doc = "A map from packages to auxilliary Go source files to load for those packages.",
+            doc = "A map from auxilliary Go source files to their packages.",
+            allow_files = True,
         ),
         "package": attr.string(
             doc = "The name of the package the generated mocks should be in. If not specified, uses mockgen's default.",
@@ -120,11 +133,6 @@ _gomock_source = rule(
             allow_single_file = True,
             mandatory = False,
         ),
-        "gopath_dep": attr.label(
-            doc = "The go_path label to use to create the GOPATH for the given library. Will be set correctly by the gomock macro, so you don't need to set it.",
-            providers = [GoPath],
-            mandatory = False,
-        ),
         "mockgen_tool": attr.label(
             doc = "The mockgen tool to run",
             default = Label(_MOCKGEN_TOOL),
@@ -146,15 +154,9 @@ def gomock(name, library, out, **kwargs):
         mockgen_tool = kwargs["mockgen_tool"]
 
     if kwargs.get("source", None):
-        gopath_name = name + "_gomock_gopath"
-        go_path(
-            name = gopath_name,
-            deps = [library, mockgen_tool],
-        )
         _gomock_source(
             name = name,
             library = library,
-            gopath_dep = gopath_name,
             out = out,
             **kwargs
         )