coverage: make crate_features key optional

Currently, if a crate wishes to run the coverage test with some cargo
features enabled, it must explicitly list them out in the
`crate_features` key of the coverage json files.

Change this so that if this key is omitted from the json file, then
test_coverage.py passes `--all-features` to cargo.

No functional change, as currently `crate_features` is a mandatory key,
so to opt-in to this new behavior, crates must remove this key from
their coverage json file(s).

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

integration_tests/test_coverage.py

@@ -49,11 +49,11 @@ def _read_test_config():
 
     assert "coverage_score" in coverage_config
     assert "exclude_path" in coverage_config
-    assert "crate_features" in coverage_config
 
-    assert (
-        " " not in coverage_config["crate_features"]
-    ), "spaces are not allowed in crate_features value"
+    if "crate_features" in coverage_config:
+        assert (
+            " " not in coverage_config["crate_features"]
+        ), "spaces are not allowed in crate_features value"
 
     return coverage_config
 
@@ -87,9 +87,11 @@ def _get_current_coverage(coverage_config, no_cleanup, test_scope):
     if test_scope == pytest.workspace:
         llvm_cov_command += " --workspace "
 
-    crate_features = coverage_config["crate_features"]
+    crate_features = coverage_config.get("crate_features")
     if crate_features:
         llvm_cov_command += " --features=" + crate_features
+    if crate_features is None:
+        llvm_cov_command += " --all-features"
 
     # Pytest closes stdin by default, but some tests might need it to be open.
     # In the future, should the need arise, we can feed custom data to stdin.