Use bazel's native json decode method

This means that `rules_jvm_external` is only compatible with
Bazel 4 and later. That shipped on 2021-01-21, and so should
be widely adopted already. Older versions of this ruleset
will continue to work for repos using older versions of Bazel
so it's not removing any existing functionality, and the new
Bazel 5 release should have already shipped.

The main reason for doing this is that the native json
decoding is significantly faster than the starlark-based one.

The following options were explored as alternatives:

1. Making the `json_parse` method check the bazel version and
   optionally use the `json` module if it was present. This
   doesn't work because of #12735

2. Create a `json` repository rule that creates a repo that
   exposes a `json.bzl` file that delegates to the native
   `json` module if present, or the starlark one if not
   (as determined by looking at the major version number of
   bazel). This doesn't work because `maven_install` is used
   by RJE's own `repositories.bzl` file, so there's no chance
   to load the repository rule before it's needed.

Links:

12735: bazelbuild/bazel#12735

BUILD

@@ -55,7 +55,6 @@ bzl_library(
         "//private/rules:maven_publish.bzl",
         "//private/rules:pom_file.bzl",
         "//settings:stamp_manifest.bzl",
-        "//third_party/bazel_json/lib:json_parser.bzl",
     ],
     visibility = [
         # This library is only visible to allow others who depend on

coursier.bzl

@@ -11,7 +11,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 
-load("//third_party/bazel_json/lib:json_parser.bzl", _json_parse = "json_parse")
 load("//private/rules:jetifier.bzl", "jetify_artifact_dependencies", "jetify_maven_coord")
 load("//:specs.bzl", "parse", "utils")
 load("//private:artifact_utilities.bzl", "deduplicate_and_sort_artifacts")
@@ -84,15 +83,6 @@ sh_binary(
 )
 """
 
-def json_parse(json_string, fail_on_invalid = True):
-    # Bazel has had a native JSON decoder since 4.0.0, but
-    # we need to support older versions of Bazel. In addition,
-    # we sometimes need to survive poorly formed JSON, so
-    # a fallback to the Starlark parser is provided.
-    if getattr(native, "json_decode", None) and not fail_on_invalid:
-        return native.json_decode(json_string)
-    return _json_parse(json_string, fail_on_invalid)
-
 def _is_verbose(repository_ctx):
     return bool(repository_ctx.os.environ.get("RJE_VERBOSE"))
 
@@ -132,7 +122,9 @@ def _execute(repository_ctx, cmd, timeout = 600, environment = {}, progress_mess
 # The representation of a Windows path when read from the parsed Coursier JSON
 # is delimited by 4 back slashes. Replace them with 1 forward slash.
 def _normalize_to_unix_path(path):
-    return path.replace("\\\\", "/")
+    if path == None:
+        return None
+    return path.replace("\\", "/")
 
 # Relativize an absolute path to an artifact in coursier's default cache location.
 # After relativizing, also symlink the path into the workspace's output base.
@@ -227,7 +219,7 @@ def _compute_dependency_tree_signature(artifacts):
         if artifact["file"] != None:
             artifact_group.extend([
                 artifact["sha256"],
-                artifact["file"],
+                artifact["file"].replace("\\", "/"),  # Make sure we represent files in a stable way cross-platform
                 artifact["url"],
             ])
         if len(artifact["dependencies"]) > 0:
@@ -243,7 +235,7 @@ def _compute_dependency_tree_signature(artifacts):
 def compute_dependency_inputs_signature(artifacts):
     artifact_inputs = []
     for artifact in artifacts:
-        parsed = json_parse(artifact)
+        parsed = json.decode(artifact)
 
         # Sort the keys to provide a stable order
         keys = sorted(parsed.keys())
@@ -385,11 +377,11 @@ def _pinned_coursier_fetch_impl(repository_ctx):
 
     repositories = []
     for repository in repository_ctx.attr.repositories:
-        repositories.append(json_parse(repository))
+        repositories.append(json.decode(repository))
 
     artifacts = []
     for artifact in repository_ctx.attr.artifacts:
-        artifacts.append(json_parse(artifact))
+        artifacts.append(json.decode(artifact))
 
     _check_artifacts_are_unique(artifacts, repository_ctx.attr.duplicate_version_warning)
 
@@ -398,11 +390,10 @@ def _pinned_coursier_fetch_impl(repository_ctx):
         repository_ctx.path(repository_ctx.attr.maven_install_json),
         repository_ctx.path("imported_maven_install.json"),
     )
-    maven_install_json_content = json_parse(
+    maven_install_json_content = json.decode(
         repository_ctx.read(
             repository_ctx.path("imported_maven_install.json"),
-        ),
-        fail_on_invalid = False,
+        )
     )
 
     # Validation steps for maven_install.json.
@@ -783,7 +774,7 @@ def make_coursier_dep_tree(
         fail("Error while fetching artifact with coursier: " + exec_result.stderr)
 
     return deduplicate_and_sort_artifacts(
-        json_parse(repository_ctx.read(repository_ctx.path("dep-tree.json"))),
+        json.decode(repository_ctx.read(repository_ctx.path("dep-tree.json"))),
         artifacts,
         excluded_artifacts,
         _is_verbose(repository_ctx),
@@ -831,17 +822,17 @@ def _coursier_fetch_impl(repository_ctx):
     # Deserialize the spec blobs
     repositories = []
     for repository in repository_ctx.attr.repositories:
-        repositories.append(json_parse(repository))
+        repositories.append(json.decode(repository))
 
     artifacts = []
     for artifact in repository_ctx.attr.artifacts:
-        artifacts.append(json_parse(artifact))
+        artifacts.append(json.decode(artifact))
 
     _check_artifacts_are_unique(artifacts, repository_ctx.attr.duplicate_version_warning)
 
     excluded_artifacts = []
     for artifact in repository_ctx.attr.excluded_artifacts:
-        excluded_artifacts.append(json_parse(artifact))
+        excluded_artifacts.append(json.decode(artifact))
 
     # Once coursier finishes a fetch, it generates a tree of artifacts and their
     # transitive dependencies in a JSON file. We use that as the source of truth
@@ -929,7 +920,8 @@ def _coursier_fetch_impl(repository_ctx):
         # that mirrors the URL where the artifact's fetched from. Using
         # this, we can reconstruct the original URL.
         primary_url_parts = []
-        filepath_parts = artifact["file"].split("/")
+        # _normalize_to_unix_path uses 2 backslashes, but the paths themselves have a single backslash at this point
+        filepath_parts = artifact["file"].replace("\\", "/").split("/")
         protocol = None
 
         # Only support http/https transports
@@ -938,7 +930,7 @@ def _coursier_fetch_impl(repository_ctx):
                 protocol = part
                 break
         if protocol == None:
-            fail("Only artifacts downloaded over http(s) are supported: %s" % artifact["coord"])
+            fail("Only artifacts downloaded over http(s) are supported: %s - %s (analyzed %s)" % (artifact["coord"], artifact["file"], filepath_parts))
         primary_url_parts.extend([protocol, "://"])
         for part in filepath_parts[filepath_parts.index(protocol) + 1:]:
             primary_url_parts.extend([part, "/"])

private/rules/maven_install.bzl

@@ -1,5 +1,5 @@
 load("//:coursier.bzl", "DEFAULT_AAR_IMPORT_LABEL", "coursier_fetch", "pinned_coursier_fetch")
-load("//:specs.bzl", "json", "parse")
+load("//:specs.bzl", _json = "json", "parse")
 load("//private:constants.bzl", "DEFAULT_REPOSITORY_NAME")
 load("//private:dependency_tree_parser.bzl", "JETIFY_INCLUDE_LIST_JETIFY_ALL")
 
@@ -77,15 +77,15 @@ def maven_install(
     """
     repositories_json_strings = []
     for repository in parse.parse_repository_spec_list(repositories):
-        repositories_json_strings.append(json.write_repository_spec(repository))
+        repositories_json_strings.append(_json.write_repository_spec(repository))
 
     artifacts_json_strings = []
     for artifact in parse.parse_artifact_spec_list(artifacts):
-        artifacts_json_strings.append(json.write_artifact_spec(artifact))
+        artifacts_json_strings.append(_json.write_artifact_spec(artifact))
 
     excluded_artifacts_json_strings = []
     for exclusion in parse.parse_exclusion_spec_list(excluded_artifacts):
-        excluded_artifacts_json_strings.append(json.write_exclusion_spec(exclusion))
+        excluded_artifacts_json_strings.append(_json.write_exclusion_spec(exclusion))
 
     if additional_netrc_lines and maven_install_json == None:
         fail("`additional_netrc_lines` is only supported with `maven_install_json` specified", "additional_netrc_lines")