java_export: Fix Make variable substitution (#960)

This requires forwarding `toolchains` to all rules as well as evaluating
Make variables for dependency coordinates in `pom_file`.

private/rules/java_export.bzl

@@ -84,6 +84,7 @@ def java_export(
     javadocopts = kwargs.pop("javadocopts", [])
     doc_deps = kwargs.pop("doc_deps", [])
     doc_url = kwargs.pop("doc_url", "")
+    toolchains = kwargs.pop("toolchains", [])
 
     # Construct the java_library we'll export from here.
     native.java_library(
@@ -108,6 +109,7 @@ def java_export(
         classifier_artifacts = classifier_artifacts,
         doc_deps = doc_deps,
         doc_url = doc_url,
+        toolchains = toolchains,
     )
 
 def maven_export(
@@ -124,7 +126,8 @@ def maven_export(
         classifier_artifacts = {},
         *,
         doc_deps = [],
-        doc_url = ""):
+        doc_url = "",
+        toolchains = None):
     """
     All arguments are the same as java_export with the addition of:
       lib_name: Name of the library that has been built.
@@ -210,6 +213,7 @@ def maven_export(
         visibility = visibility,
         tags = tags + maven_coordinates_tags,
         testonly = testonly,
+        toolchains = toolchains,
     )
 
     native.filegroup(
@@ -251,6 +255,7 @@ def maven_export(
             visibility = visibility,
             tags = tags,
             testonly = testonly,
+            toolchains = toolchains,
         )
         classifier_artifacts.setdefault("javadoc", docs_jar)
 
@@ -262,6 +267,7 @@ def maven_export(
         visibility = visibility,
         tags = tags,
         testonly = testonly,
+        toolchains = toolchains,
     )
 
     maven_publish(
@@ -273,6 +279,7 @@ def maven_export(
         visibility = visibility,
         tags = tags,
         testonly = testonly,
+        toolchains = toolchains,
     )
 
     # We may want to aggregate several `java_export` targets into a single Maven BOM POM
@@ -287,6 +294,7 @@ def maven_export(
         testonly = testonly,
         tags = tags,
         visibility = visibility,
+        toolchains = toolchains,
     )
 
     # Finally, alias the primary output

private/rules/pom_file.bzl

@@ -15,14 +15,18 @@ def _pom_file_impl(ctx):
     for dep in additional_deps:
         for coords in dep[MavenInfo].as_maven_dep.to_list():
             all_maven_deps.append(coords)
+    expanded_maven_deps = [
+        ctx.expand_make_variables("additional_deps", coords, ctx.var)
+        for coords in all_maven_deps
+    ]
 
     # Expand maven coordinates for any variables to be replaced.
     coordinates = ctx.expand_make_variables("coordinates", info.coordinates, ctx.var)
 
     out = generate_pom(
         ctx,
         coordinates = coordinates,
-        versioned_dep_coordinates = sorted(all_maven_deps),
+        versioned_dep_coordinates = sorted(expanded_maven_deps),
         pom_template = ctx.file.pom_template,
         out_name = "%s.xml" % ctx.label.name,
     )