nogo: use bazel validations and don't fail compile

go/private/actions/archive.bzl

@@ -62,9 +62,17 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
     out_export = go.declare_file(go, name = source.library.name, ext = pre_ext + ".x")
     out_cgo_export_h = None  # set if cgo used in c-shared or c-archive mode
 
+    # capture the nogo_log output but don't fail the compile, later we assert that the log is empty
+    out_nogo_log = None
+    out_nogo_validation = None
+    if go.nogo:
+        out_nogo_log = go.declare_file(go, name = source.library.name, ext = pre_ext + ".nogo.log")
+        out_nogo_validation = go.declare_file(go, name = source.library.name, ext = pre_ext + ".nogo")
+
     direct = [get_archive(dep) for dep in source.deps]
     runfiles = source.runfiles
     data_files = runfiles.files
+    validations = []
 
     files = []
     for a in direct:
@@ -106,6 +114,7 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
             out_lib = out_lib,
             out_export = out_export,
             out_cgo_export_h = out_cgo_export_h,
+            out_nogo_log = out_nogo_log,
             gc_goopts = source.gc_goopts,
             cgo = True,
             cgo_inputs = cgo.inputs,
@@ -129,12 +138,28 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
             archives = direct,
             out_lib = out_lib,
             out_export = out_export,
+            out_nogo_log = out_nogo_log,
             gc_goopts = source.gc_goopts,
             cgo = False,
             testfilter = testfilter,
             recompile_internal_deps = recompile_internal_deps,
         )
 
+    if go.nogo:
+        validations.append(out_nogo_validation)
+        go.actions.run_shell(
+            inputs = [out_nogo_log],
+            outputs = [out_nogo_validation],
+            # Create the expected output file if there are no errors, otherwise print the errors to stderr.
+            command = '[ -s "$1" ] && cat <(echo) "$1" <(echo) 1>&2 || touch $2',
+            arguments = [
+                out_nogo_log.path,
+                out_nogo_validation.path,
+            ],
+            progress_message = "Nogo Static Analysis",
+            mnemonic = "GoNogo",
+        )
+
     data = GoArchiveData(
         # TODO(#2578): reconsider the provider API. There's a lot of redundant
         # information here. Some fields are tuples instead of lists or dicts
@@ -198,4 +223,5 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
         cgo_exports = cgo_exports,
         runfiles = runfiles,
         mode = go.mode,
+        validations = validations,
     )

go/private/actions/compilepkg.bzl

@@ -54,6 +54,7 @@ def emit_compilepkg(
         clinkopts = [],
         out_lib = None,
         out_export = None,
+        out_nogo_log = None,
         out_cgo_export_h = None,
         gc_goopts = [],
         testfilter = None,  # TODO: remove when test action compiles packages
@@ -112,6 +113,9 @@ def emit_compilepkg(
     if go.nogo:
         args.add("-nogo", go.nogo)
         inputs.append(go.nogo)
+        if out_nogo_log:
+            args.add("-nogo_log", out_nogo_log.path)
+            outputs.append(out_nogo_log)
     if out_cgo_export_h:
         args.add("-cgoexport", out_cgo_export_h)
         outputs.append(out_cgo_export_h)

go/private/rules/binary.bzl

@@ -129,6 +129,7 @@ def _go_binary_impl(ctx):
         OutputGroupInfo(
             cgo_exports = archive.cgo_exports,
             compilation_outputs = [archive.data.file],
+            _validation = depset(archive.validations),
         ),
     ]
 

go/private/rules/library.bzl

@@ -61,6 +61,7 @@ def _go_library_impl(ctx):
         OutputGroupInfo(
             cgo_exports = archive.cgo_exports,
             compilation_outputs = [archive.data.file],
+            _validation = depset(archive.validations),
         ),
     ]
 

go/private/rules/test.bzl

@@ -182,6 +182,7 @@ def _go_test_impl(ctx):
         ),
         OutputGroupInfo(
             compilation_outputs = [internal_archive.data.file],
+            _validation = test_archive.validations,
         ),
         coverage_common.instrumented_files_info(
             ctx,

go/tools/builders/compilepkg.go

@@ -51,7 +51,7 @@ func compilePkg(args []string) error {
 	goenv := envFlags(fs)
 	var unfilteredSrcs, coverSrcs, embedSrcs, embedLookupDirs, embedRoots, recompileInternalDeps multiFlag
 	var deps archiveMultiFlag
-	var importPath, packagePath, nogoPath, packageListPath, coverMode string
+	var importPath, packagePath, nogoPath, nogoLogPath, packageListPath, coverMode string
 	var outPath, outFactsPath, cgoExportHPath string
 	var testFilter string
 	var gcFlags, asmFlags, cppFlags, cFlags, cxxFlags, objcFlags, objcxxFlags, ldFlags quoteMultiFlag
@@ -74,6 +74,7 @@ func compilePkg(args []string) error {
 	fs.Var(&objcxxFlags, "objcxxflags", "Objective-C++ compiler flags")
 	fs.Var(&ldFlags, "ldflags", "C linker flags")
 	fs.StringVar(&nogoPath, "nogo", "", "The nogo binary. If unset, nogo will not be run.")
+	fs.StringVar(&nogoLogPath, "nogo_log", "", "The path of the nogo log to write to. Required if -nogo is set.")
 	fs.StringVar(&packageListPath, "package_list", "", "The file containing the list of standard library packages")
 	fs.StringVar(&coverMode, "cover_mode", "", "The coverage mode to use. Empty if coverage instrumentation should not be added.")
 	fs.StringVar(&outPath, "o", "", "The output archive file to write compiled code")
@@ -158,6 +159,7 @@ func compilePkg(args []string) error {
 		objcxxFlags,
 		ldFlags,
 		nogoPath,
+		nogoLogPath,
 		packageListPath,
 		outPath,
 		outFactsPath,
@@ -189,6 +191,7 @@ func compileArchive(
 	objcxxFlags []string,
 	ldFlags []string,
 	nogoPath string,
+	nogoLogPath string,
 	packageListPath string,
 	outPath string,
 	outXPath string,
@@ -449,18 +452,25 @@ func compileArchive(
 		// Add unknown origin source files into the mix.
 		nogoSrcs = append(nogoSrcs, goSrc)
 	}
-	if nogoPath != "" && len(nogoSrcs) > 0 {
-		ctx, cancel := context.WithCancel(context.Background())
-		nogoChan = make(chan error)
-		go func() {
-			nogoChan <- runNogo(ctx, workDir, nogoPath, nogoSrcs, deps, packagePath, importcfgPath, outFactsPath)
-		}()
-		defer func() {
-			if nogoChan != nil {
-				cancel()
-				<-nogoChan
-			}
-		}()
+	if nogoPath != "" {
+		nogoLogFile, err := os.OpenFile(nogoLogPath, os.O_CREATE|os.O_RDWR, 0644)
+		if err != nil {
+			return fmt.Errorf("error opening nogo log file: %v", err)
+		}
+		defer nogoLogFile.Close()
+		if len(nogoSrcs) > 0 {
+			ctx, cancel := context.WithCancel(context.Background())
+			nogoChan = make(chan error)
+			go func() {
+				nogoChan <- runNogo(ctx, workDir, nogoPath, nogoSrcs, deps, packagePath, importcfgPath, outFactsPath, nogoLogFile)
+			}()
+			defer func() {
+				if nogoChan != nil {
+					cancel()
+					<-nogoChan
+				}
+			}()
+		}
 	}
 
 	// If there are Go assembly files and this is go1.12+: generate symbol ABIs.
@@ -577,7 +587,7 @@ func compileGo(goenv *env, srcs []string, packagePath, importcfgPath, embedcfgPa
 	return goenv.runCommand(args)
 }
 
-func runNogo(ctx context.Context, workDir string, nogoPath string, srcs []string, deps []archive, packagePath, importcfgPath, outFactsPath string) error {
+func runNogo(ctx context.Context, workDir string, nogoPath string, srcs []string, deps []archive, packagePath, importcfgPath, outFactsPath string, logFile *os.File) error {
 	args := []string{nogoPath}
 	args = append(args, "-p", packagePath)
 	args = append(args, "-importcfg", importcfgPath)
@@ -601,7 +611,10 @@ func runNogo(ctx context.Context, workDir string, nogoPath string, srcs []string
 				cmdLine := strings.Join(args, " ")
 				return fmt.Errorf("nogo command '%s' exited unexpectedly: %s", cmdLine, exitErr.String())
 			}
-			return errors.New(string(relativizePaths(out.Bytes())))
+			_, err := logFile.Write(relativizePaths(out.Bytes()))
+			if err != nil {
+				return fmt.Errorf("error writing nogo log: %v", err)
+			}
 		} else {
 			if out.Len() != 0 {
 				fmt.Fprintln(os.Stderr, out.String())

go/tools/builders/nogo_main.go

@@ -87,14 +87,14 @@ func run(args []string) error {
 	if err != nil {
 		return fmt.Errorf("error running analyzers: %v", err)
 	}
-	if diagnostics != "" {
-		return fmt.Errorf("errors found by nogo during build-time code analysis:\n%s\n", diagnostics)
-	}
 	if *xPath != "" {
 		if err := ioutil.WriteFile(abs(*xPath), facts, 0o666); err != nil {
 			return fmt.Errorf("error writing facts: %v", err)
 		}
 	}
+	if diagnostics != "" {
+		return fmt.Errorf("errors found by nogo during build-time code analysis:\n%s\n", diagnostics)
+	}
 
 	return nil
 }