wip: Implement Test Coverage Reporting

Author: maennchen

.github/workflows/ci.yml

@@ -21,13 +21,16 @@ permissions:
 
 jobs:
   test_linux:
-    name: Ubuntu 24.04, Erlang/OTP ${{ matrix.otp_version }}${{ matrix.deterministic && ' (deterministic)' || '' }}
+    name: Ubuntu 24.04, Erlang/OTP ${{ matrix.otp_version }}${{ matrix.deterministic && ' (deterministic)' || '' }}${{ matrix.coverage && ' (coverage)' || '' }}
     strategy:
       fail-fast: false
       matrix:
         include:
           - otp_version: "27.1"
             deterministic: true
+          - otp_version: "27.1"
+            erlc_opts: "warnings_as_errors"
+            coverage: true
           - otp_version: "27.1"
             otp_latest: true
             erlc_opts: "warnings_as_errors"
@@ -65,9 +68,14 @@ jobs:
       - name: Erlang test suite
         run: make test_erlang
         continue-on-error: ${{ matrix.development }}
+        if: "${{ !matrix.coverage }}"
       - name: Elixir test suite
         run: make test_elixir
         continue-on-error: ${{ matrix.development }}
+        if: "${{ !matrix.coverage }}"
+      - name: "Calculate Coverage"
+        run: make cover
+        if: "${{ matrix.coverage }}"
       - name: Build docs (ExDoc main)
         if: ${{ matrix.otp_latest }}
         run: |
@@ -85,6 +93,12 @@ jobs:
           # Recompile System without .git
           cd lib/elixir && ../../bin/elixirc -o ebin lib/system.ex && cd -
           taskset 1 make check_reproducible
+      - name: "Upload Coverage Artifact"
+        if: "${{ matrix.coverage }}"
+        uses: actions/upload-artifact@4cec3d8aa04e39d1a68397de0c4cd6fb9dce8ec1 # v4.6.1
+        with:
+          name: TestCoverage
+          path: cover/*
 
   test_windows:
     name: Windows Server 2019, Erlang/OTP ${{ matrix.otp_version }}

.gitignore

@@ -15,3 +15,4 @@
 /.eunit
 .elixir.plt
 erl_crash.dump
+/cover/

Makefile

@@ -53,6 +53,11 @@ lib/$(1)/ebin/Elixir.$(2).beam: $(wildcard lib/$(1)/lib/*.ex) $(wildcard lib/$(1
 test_$(1): test_formatted $(1)
 	@ echo "==> $(1) (ex_unit)"
 	$(Q) cd lib/$(1) && ../../bin/elixir -r "test/test_helper.exs" -pr "test/**/$(TEST_FILES)";
+
+cover/exunit_$(1).coverdata:
+	$(Q) mkdir -p cover
+	$(Q) COVER_FILE="cover/exunit_$(1).coverdata" $(MAKE) test_$(1)
+cover/combined.coverdata: cover/exunit_$(1).coverdata
 endef
 
 define WRITE_SOURCE_DATE_EPOCH
@@ -175,6 +180,7 @@ clean: clean_man
 	rm -rf lib/mix/test/fixtures/git_sparse_repo/
 	rm -rf lib/mix/test/fixtures/archive/ebin/
 	rm -f erl_crash.dump
+	rm -rf cover/*
 
 clean_elixir:
 	$(Q) rm -f lib/*/ebin/Elixir.*.beam
@@ -287,6 +293,22 @@ test_stdlib: compile
 		cd lib/elixir && ../../bin/elixir --sname primary -r "test/elixir/test_helper.exs" -pr "test/elixir/**/$(TEST_FILES)"; \
 	fi
 
+cover/exunit_stdlib.coverdata:
+	$(Q) mkdir -p cover
+	$(Q) COVER_FILE="$(realpath cover)/exunit_stdlib.coverdata" $(MAKE) test_stdlib
+cover/combined.coverdata: cover/exunit_stdlib.coverdata
+
+cover/eunit_stdlib.coverdata:
+	$(Q) mkdir -p cover
+	$(Q) COVER_FILE="$(realpath cover)/eunit_stdlib.coverdata" $(MAKE) test_erlang
+cover/combined.coverdata: cover/eunit_stdlib.coverdata
+
+cover/combined.coverdata:
+	$(Q) bin/elixir ./lib/elixir/scripts/cover.exs
+
+.PHONY: cover
+cover: cover/combined.coverdata
+
 #==> Dialyzer tasks
 
 DIALYZER_OPTS = --no_check_plt --fullpath -Werror_handling -Wunmatched_returns -Wunderspecs

lib/eex/test/test_helper.exs

@@ -5,6 +5,8 @@
 {line_exclude, line_include} =
   if line = System.get_env("LINE"), do: {[:test], [line: line]}, else: {[], []}
 
+Code.eval_file("../../../elixir/scripts/cover_record.exs", __ENV__.file)
+
 ExUnit.start(
   trace: !!System.get_env("TRACE"),
   include: line_include,

lib/elixir/scripts/cover.exs

@@ -0,0 +1,42 @@
+#!bin/elixir
+
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: 2021 The Elixir Team
+
+root_dir = __ENV__.file |> Path.dirname() |> Path.join("../../..")
+cover_dir = Path.join(root_dir, "cover")
+coverdata_inputs = cover_dir |> Path.join("{exunit,eunit}_*.coverdata") |> Path.wildcard()
+coverdata_output = Path.join(cover_dir, "combined.coverdata")
+ebins = root_dir |> Path.join("lib/*/ebin") |> Path.wildcard()
+
+_ = :cover.stop()
+{:ok, cover_pid} = :cover.start()
+
+for ebin <- ebins,
+    result <- :cover.compile_beam_directory(String.to_charlist(ebin)) do
+  case result do
+    {:ok, _module} ->
+      :ok
+
+    {:error, reason} ->
+      raise "Failed to cover compile directory #{ebin} with reason: #{inspect(reason)}"
+  end
+end
+
+for file <- coverdata_inputs do
+  :ok = :cover.import(String.to_charlist(file))
+end
+
+:ok = :cover.export(String.to_charlist(coverdata_output))
+
+{:ok, _} = Application.ensure_all_started(:mix)
+
+# Silence analyse import messages emitted by cover
+{:ok, string_io} = StringIO.open("")
+Process.group_leader(cover_pid, string_io)
+
+:ok =
+  Mix.Tasks.Test.Coverage.generate_cover_results(
+    output: cover_dir,
+    summary: [threshold: 0]
+  )

lib/elixir/scripts/cover_record.exs

@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: 2021 The Elixir Team
+
+root_dir = __ENV__.file |> Path.dirname() |> Path.join("../../..")
+ebins = root_dir |> Path.join("lib/*/ebin") |> Path.wildcard()
+
+case System.fetch_env("COVER_FILE") do
+  {:ok, file} ->
+    _ = :cover.stop()
+    {:ok, _pid} = :cover.start()
+
+    for ebin <- ebins,
+        result <- :cover.compile_beam_directory(String.to_charlist(ebin)) do
+      case result do
+        {:ok, _module} ->
+          :ok
+
+        {:error, reason} ->
+          raise "Failed to cover compile directory #{ebin} with reason: #{inspect(reason)}"
+      end
+    end
+
+    System.at_exit(fn _status ->
+      :ok = :cover.export(String.to_charlist(file))
+    end)
+
+    true
+
+  :error ->
+    false
+end

lib/elixir/test/elixir/exception_test.exs

@@ -556,7 +556,9 @@ defmodule ExceptionTest do
     end
 
     test "annotates function clause errors" do
-      assert blame_message(Access, & &1.fetch(:foo, :bar)) =~ """
+      message = blame_message(Access, & &1.fetch(:foo, :bar))
+
+      assert message =~ """
              no function clause matching in Access.fetch/2
 
              The following arguments were given to Access.fetch/2:
@@ -566,11 +568,15 @@ defmodule ExceptionTest do
 
                  # 2
                  :bar
+             """
 
-             Attempted function clauses (showing 5 out of 5):
+      if Access not in :cover.modules() do
+        assert message =~ """
+               Attempted function clauses (showing 5 out of 5):
 
-                 def fetch(-%module{} = container-, key)
-             """
+                   def fetch(-%module{} = container-, key)
+               """
+      end
     end
 
     test "annotates undefined function error with suggestions" do
@@ -863,10 +869,16 @@ defmodule ExceptionTest do
       {exception, stack} =
         Exception.blame(:error, :function_clause, [{Keyword, :pop, args, [line: 13]}])
 
-      assert %FunctionClauseError{kind: :def, args: ^args, clauses: [_]} = exception
+      if Keyword in :cover.modules() do
+        assert %FunctionClauseError{kind: nil, args: ^args, clauses: nil} = exception
+      else
+        assert %FunctionClauseError{kind: :def, args: ^args, clauses: [_]} = exception
+      end
+
       assert stack == [{Keyword, :pop, 3, [line: 13]}]
     end
 
+    @tag :require_ast
     test "annotates args and clauses from mfa" do
       import PathHelpers
 

lib/elixir/test/elixir/kernel/dialyzer_test.exs

@@ -8,6 +8,7 @@ defmodule Kernel.DialyzerTest do
   use ExUnit.Case, async: true
 
   @moduletag :dialyzer
+  @moduletag :require_ast
   import PathHelpers
 
   setup_all do

lib/elixir/test/elixir/module/types/integration_test.exs

@@ -458,6 +458,7 @@ defmodule Module.Types.IntegrationTest do
       assert_warnings(files, warnings)
     end
 
+    @tag :require_ast
     test "String.Chars protocol dispatch" do
       files = %{
         "a.ex" => """
@@ -520,6 +521,7 @@ defmodule Module.Types.IntegrationTest do
       assert_warnings(files, warnings, consolidate_protocols: true)
     end
 
+    @tag :require_ast
     test "Enumerable protocol dispatch" do
       files = %{
         "a.ex" => """

lib/elixir/test/elixir/module_test.exs

@@ -431,6 +431,7 @@ defmodule ModuleTest do
     assert backend.debug_info(:elixir_v1, ModuleCreateNoDebugInfo, data, []) == {:error, :missing}
   end
 
+  @tag :require_ast
   test "compiles to core" do
     {:ok, {Atom, [{~c"Dbgi", dbgi}]}} = Atom |> :code.which() |> :beam_lib.chunks([~c"Dbgi"])
     {:debug_info_v1, backend, data} = :erlang.binary_to_term(dbgi)