Workaround for inconsistent order of llvm-cov results on Windows

Author: richkadel

src/test/run-make-fulldeps/coverage-reports/Makefile

@@ -22,6 +22,43 @@ ifeq ($(LLVM_COV_DEBUG), 1)
 DEBUG_FLAG=--debug
 endif
 
+# FIXME(richkadel): I'm adding `--ignore-filename-regex=` line(s) for specific test(s) that produce
+# `llvm-cov` results for multiple files (for example `uses_crate.rs` and `used_crate/mod.rs`) as a
+# workaround for two problems causing tests to fail on Windows:
+#
+# 1. When multiple files appear in the `llvm-cov show` results, each file's coverage results can
+#    appear in different a different order. Whether this is random or, somehow, platform-specific,
+#    the Windows output flips the order of the files, compared to Linux. In the `uses_crate.rs`
+#    test, the only test-unique (interesting) results we care about are the results for only one
+#    of the two files, `mod/uses_crate.rs`, so the workaround is to ignore all but this one file.
+#    In the future, we may want a more sophisticated solution that splits apart `llvm-cov show`
+#    results into separate results files for each result (taking care not to create new file
+#    paths that might be too long for Windows MAX_PATH limits when creating these new sub-results,
+#    as well).
+# 2. When multiple files appear in the `llvm-cov show` results, the results for each file are
+#    prefixed with their filename, including platform-specific path separators (`\` for Windows,
+#    and `/` everywhere else). This could be filtered or normalized of course, but by ignoring
+#    coverage results for all but one of the file, the filenames are no longer included anyway.
+#    If this changes (if/when we decide to support `llvm-cov show` results for multiple files),
+#    the file path separator differences may need to be addressed.
+#
+# Since this is only a workaround, I decided to implement the override by adding an option for
+# each file to be ignored, using a `--ignore-filename-regex=` entry for each one, rather than
+# implement some more sophisticated solution with a new custom test directive in the test file
+# itself (similar to `expect-exit-status`) because that would add a lot of complexity and still
+# be a workaround, with the same result, with no benefit.
+#
+# Yes these `--ignore-filename-regex=` options are included in all invocations of `llvm-cov show`
+# for now, but it is effectively ignored for all tests that don't include this file anyway.
+#
+# Note that it's also possible the `_counters.<test>.txt` and `<test>.json` files may order
+# results from multiple files inconsistently, which might also have to be accomodated if and when
+# we allow `llvm-cov` to produce results for multiple files. (The path separators appear to be
+# normalized to `/` in those files, thankfully.) But since we are ignoring results for all but one
+# file, this workaround addresses those potential issues as well.
+LLVM_COV_IGNORE_FILES=\
+	--ignore-filename-regex=uses_crate.rs
+
 # When generating `expected_*` results (using `x.py test --bless`), the `--debug` flag is forced.
 # If assertions are disabled, the command will fail with an error, rather than attempt to generate
 # only partial results.
@@ -76,6 +113,7 @@ endif
 	# Generate a coverage report using `llvm-cov show`.
 	"$(LLVM_BIN_DIR)"/llvm-cov show \
 			$(DEBUG_FLAG) \
+			$(LLVM_COV_IGNORE_FILES) \
 			--Xdemangler="$(RUST_DEMANGLER)" \
 			--show-line-counts-or-regions \
 			--instr-profile="$(TMPDIR)"/$@.profdata \
@@ -133,6 +171,7 @@ endif
 	# Generate a coverage report in JSON, using `llvm-cov export`, and fail if
 	# there are differences from the expected output.
 	"$(LLVM_BIN_DIR)"/llvm-cov export \
+			$(LLVM_COV_IGNORE_FILES) \
 			--summary-only \
 			--instr-profile="$(TMPDIR)"/$@.profdata \
 			$(call BIN,"$(TMPDIR)"/$@) \

src/test/run-make-fulldeps/coverage-reports/expected_export_coverage.uses_crate.json

@@ -27,55 +27,29 @@
               "percent": 37.5
             }
           }
-        },
-        {
-          "filename": "../coverage/uses_crate.rs",
-          "summary": {
-            "functions": {
-              "count": 1,
-              "covered": 1,
-              "percent": 100
-            },
-            "instantiations": {
-              "count": 1,
-              "covered": 1,
-              "percent": 100
-            },
-            "lines": {
-              "count": 6,
-              "covered": 6,
-              "percent": 100
-            },
-            "regions": {
-              "count": 1,
-              "covered": 1,
-              "notcovered": 0,
-              "percent": 100
-            }
-          }
         }
       ],
       "totals": {
         "functions": {
-          "count": 4,
-          "covered": 4,
+          "count": 3,
+          "covered": 3,
           "percent": 100
         },
         "instantiations": {
-          "count": 5,
-          "covered": 5,
+          "count": 4,
+          "covered": 4,
           "percent": 100
         },
         "lines": {
-          "count": 37,
-          "covered": 20,
-          "percent": 54.054054054054056
+          "count": 31,
+          "covered": 14,
+          "percent": 45.16129032258064
         },
         "regions": {
-          "count": 17,
-          "covered": 7,
+          "count": 16,
+          "covered": 6,
           "notcovered": 10,
-          "percent": 41.17647058823529
+          "percent": 37.5
         }
       }
     }

src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.uses_crate.txt

@@ -1,4 +1,3 @@
-../coverage/used_crate/mod.rs:
     1|       |#![allow(unused_assignments, unused_variables)]
     2|       |
     3|       |use std::fmt::Debug;
@@ -55,15 +54,3 @@
    42|      0|    }
    43|      0|}
 
-../coverage/uses_crate.rs:
-    1|       |#![allow(unused_assignments, unused_variables)]
-    2|       |
-    3|       |mod used_crate;
-    4|       |
-    5|      1|fn main() {
-    6|      1|    used_crate::used_function();
-    7|      1|    let some_vec = vec![1, 2, 3, 4];
-    8|      1|    used_crate::used_generic_function(&some_vec);
-    9|      1|    used_crate::used_twice_generic_function(some_vec);
-   10|      1|}
-

src/test/run-make-fulldeps/coverage-reports/expected_show_coverage_counters.uses_crate.txt

@@ -73,8 +73,3 @@ Combined regions:
   21:1 -> 23:2 (count=1)
 Segment at 21:1 (count = 1), RegionEntry
 Segment at 23:2 (count = 0), Skipped
-Emitting segments for file: ../coverage/uses_crate.rs
-Combined regions:
-  5:1 -> 10:2 (count=1)
-Segment at 5:1 (count = 1), RegionEntry
-Segment at 10:2 (count = 0), Skipped