Remove redundant and unreliable coverage test results

The `coverage-reports` tests still generate counters and JSON reports
for inspection, but these files are no longer used in Makefile diffs, to
reduce complexity and confusion from unreliable or unexpected test
results, especially when maintaining them (i.e., generating `--bless`ed
results).

The associated `expected_` files for counters and JSON reports have been
removed, leaving only the files actually used for testing: the `llvm-cov
show` reports.

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

@@ -9,11 +9,13 @@
 BASEDIR=../coverage-reports
 SOURCEDIR=../coverage
 
-# The `llvm-cov show` flag `--debug`, used to generate the `counters` output files, is only enabled
-# if LLVM assertions are enabled. Requires Rust config `llvm/optimize` and not
+# The `llvm-cov show` flag `--debug`, used to generate the `counters` output files, is only
+# enabled if LLVM assertions are enabled. This requires Rust config `llvm/optimize` and not
 # `llvm/release_debuginfo`. Note that some CI builds disable debug assertions (by setting
-# `NO_LLVM_ASSERTIONS=1`), so it is not OK to fail the test, but `bless`ed test results cannot be
-# generated without debug assertions.
+# `NO_LLVM_ASSERTIONS=1`), so the tests must still pass even if the `--debug` flag is
+# not supported. (Note that `counters` files are only produced in the `$(TMPDIR)`
+# directory, for inspection and debugging support. They are *not* copied to `expected_*`
+# files when `--bless`ed.)
 LLVM_COV_DEBUG := $(shell \
 		"$(LLVM_BIN_DIR)"/llvm-cov show --debug 2>&1 | \
 		grep -q "Unknown command line argument '--debug'"; \
@@ -51,11 +53,10 @@ endif
 # 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.
+# (Note that it's also possible the `_counters.<test>.txt` and `<test>.json` files (if generated)
+# 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. Note, the path separators
+# appear to be normalized to `/` in those files, thankfully.)
 LLVM_COV_IGNORE_FILES=\
 	--ignore-filename-regex=uses_crate.rs
 
@@ -77,9 +78,7 @@ endif
 .PHONY: clear_expected_if_blessed
 clear_expected_if_blessed:
 ifdef RUSTC_BLESS_TEST
-	rm -f expected_export_coverage.*.json
-	rm -f expected_show_coverage.*.txt
-	rm -f expected_show_coverage_counters.*.txt
+	rm -f expected_*
 endif
 
 -include clear_expected_if_blessed
@@ -140,12 +139,8 @@ endif
 ifdef RUSTC_BLESS_TEST
 	cp "$(TMPDIR)"/actual_show_coverage.$@.txt \
 			expected_show_coverage.$@.txt
-	cp "$(TMPDIR)"/actual_show_coverage_counters.$@.txt \
-			expected_show_coverage_counters.$@.txt
 else
-	# Compare the show coverage output (`--bless` refreshes `typical` files)
-	# Note `llvm-cov show` output for some programs can vary, but can be ignored
-	# by inserting `// ignore-llvm-cov-show-diffs` at the top of the source file.
+	# Compare the show coverage output (`--bless` refreshes `typical` files).
 	#
 	# FIXME(richkadel): None of the Rust test source samples have the
 	# `// ignore-llvm-cov-show-diffs` anymore. This directive exists to work around a limitation
@@ -158,8 +153,10 @@ else
 	#
 	# This workaround only works if the coverage counts are identical across all reported
 	# instantiations. If there is no way to ensure this, you may need to apply the
-	# `// ignore-llvm-cov-show-diffs` directive, and rely on the `.json` and counter
-	# files for validating results have not changed.
+	# `// ignore-llvm-cov-show-diffs` directive, and check for differences using the
+	# `.json` files to validate that results have not changed. (Until then, the JSON
+	# files are redundant, so there is no need to generate `expected_*.json` files or
+	# compare actual JSON results.)
 
 	$(DIFF) --ignore-matching-lines='::<.*>.*:$$' \
 		expected_show_coverage.$@.txt "$(TMPDIR)"/actual_show_coverage.$@.txt || \
@@ -169,37 +166,77 @@ else
 		( >&2 echo 'diff failed, and not suppressed without `// ignore-llvm-cov-show-diffs` in $(SOURCEDIR)/$@.rs'; \
 			false \
 		)
-
-ifdef DEBUG_FLAG
-	$(DIFF) expected_show_coverage_counters.$@.txt "$(TMPDIR)"/actual_show_coverage_counters.$@.txt || \
-		( grep -q '^\/\/ ignore-llvm-cov-show-diffs' $(SOURCEDIR)/$@.rs && \
-			>&2 echo 'diff failed, but suppressed with `// ignore-llvm-cov-show-diffs` in $(SOURCEDIR)/$@.rs' \
-		) || \
-		( >&2 echo 'diff failed, and not suppressed without `// ignore-llvm-cov-show-diffs` in $(SOURCEDIR)/$@.rs'; \
-			>&2 echo '(Ignore anyway until mangled function names in "counters" files are demangled.)' \
-		)
-
-		# FIXME(richkadel): Apply the demangler to the `*_show_coverage_counters.*.txt` files,
-		# so the crate disambiguator differences will be stripped away. At that point, these files
-		# will be less likely to vary, and the last `echo` above (starting with "Ignore anyway")
-		# can be replaced with `false` to fail the test.
 endif
 
-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)"/$@) \
-		| "$(PYTHON)" $(BASEDIR)/prettify_json.py \
-		> "$(TMPDIR)"/actual_export_coverage.$@.json
+# The following Makefile content was used to copy the generated `counters` files
+# to `expected_` files (when `--bless`ed) and to compare them via `diff`; but for
+# multiple reasons, these files cannot easily be used for test validation:
+#
+#   * Output lines can be produced in non-deterministic order (depending on the
+#     target platform, and sometimes on unrelated codegen changes).
+#   * Some lines include demangled function names, making them more challenging
+#     to interpret and compare.
+#
+# The files are still generated (in `$(TMPDIR)`) to support developers wanting
+# to inspect the counters, for debugging purposes.
+#
+# ifdef RUSTC_BLESS_TEST
+# 	cp "$(TMPDIR)"/actual_show_coverage_counters.$@.txt \
+# 			expected_show_coverage_counters.$@.txt
+# else
+#
+# ifdef DEBUG_FLAG
+# 	$(DIFF) expected_show_coverage_counters.$@.txt "$(TMPDIR)"/actual_show_coverage_counters.$@.txt || \
+# 		( grep -q '^\/\/ ignore-llvm-cov-show-diffs' $(SOURCEDIR)/$@.rs && \
+# 			>&2 echo 'diff failed, but suppressed with `// ignore-llvm-cov-show-diffs` in $(SOURCEDIR)/$@.rs' \
+# 		) || \
+# 		( >&2 echo 'diff failed, and not suppressed without `// ignore-llvm-cov-show-diffs` in $(SOURCEDIR)/$@.rs'; \
+# 			>&2 echo '(Ignore anyway until mangled function names in "counters" files are demangled.)' \
+# 		)
+# endif
+#
+# endif
 
-ifdef RUSTC_BLESS_TEST
-	cp "$(TMPDIR)"/actual_export_coverage.$@.json expected_export_coverage.$@.json
-else
-	# Check that exported JSON coverage data matches what we expect (`--bless` refreshes `expected`)
-	$(DIFF) expected_export_coverage.$@.json "$(TMPDIR)"/actual_export_coverage.$@.json
-endif
+####################################################################################################
+
+# The following Makefile content, and short JSON script, were used to generate
+# coverage reports in JSON when the `llvm-cov show` reports were less reliable for
+# testing. At the present time, however, the `llvm-cov show` results, and methods
+# for comparing them, are working for all tests, making the JSON reports redundant.
+#
+# If this changes in the future, the scripts are left here, commented out, but can
+# be resurrected if desired. This could be used to compare *only* the JSON files;
+# and in that case, the `llvm-cov show` reports can be ignored by inserting
+# `// ignore-llvm-cov-show-diffs` at the top of the source file.
+#
+# 	# 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)"/$@) \
+# 		| "$(PYTHON)" $(BASEDIR)/prettify_json.py \
+# 		> "$(TMPDIR)"/actual_export_coverage.$@.json
+#
+# ifdef RUSTC_BLESS_TEST
+# 	cp "$(TMPDIR)"/actual_export_coverage.$@.json expected_export_coverage.$@.json
+# else
+# 	# Check that exported JSON coverage data matches what we expect (`--bless` refreshes `expected`)
+# 	$(DIFF) expected_export_coverage.$@.json "$(TMPDIR)"/actual_export_coverage.$@.json
+# endif
+#
+# # # If generating coverage reports in JSON, this Makefile is accompanied by
+# # # a Python script, `prettify_json.py`, which is defined:
+# #
+# # #!/usr/bin/env python
+# #
+# # import sys
+# # import json
+# #
+# # # Try to decode line in order to ensure it is a valid JSON document
+# # for line in sys.stdin:
+# #     parsed = json.loads(line)
+# #     print (json.dumps(parsed, indent=2, separators=(',', ': '), sort_keys=True))