Do not ignore command errors in ExecRecipeCollectStdErr

Previously, this function would ignore any errors returned by `Run()`
since the command is expected to fail in most cases. However, in
addition to ignoring a non-zero exit code from the command, it would
also ignore errors in running the command itself.

With this commit, `ExecRecipeCollectStdErr()` simply returns all errors,
but its caller checks the type of the error. If it is `ExitError`, this
indicates a non-zero exit status, which is ignored. Otherwise, the error
is reported as normal.

Signed-off-by: Matthijs Kooijman <matthijs@stdin.nl>

builder_utils/utils.go

@@ -410,8 +410,8 @@ func ExecRecipeCollectStdErr(buildProperties properties.Map, recipe string, remo
 
 	buffer := &bytes.Buffer{}
 	command.Stderr = buffer
-	command.Run()
-	return string(buffer.Bytes()), nil
+	err = command.Run()
+	return string(buffer.Bytes()), err
 }
 
 func RemoveHyphenMDDFlagFromGCCCommandLine(buildProperties properties.Map) {

container_find_includes.go

@@ -110,6 +110,7 @@ import (
 	"encoding/json"
 	"io/ioutil"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"time"
 
@@ -324,7 +325,12 @@ func findIncludesUntilDone(ctx *types.Context, cache *includeCache, sourceFile t
 			}
 		} else {
 			stderr, err := GCCPreprocRunnerForDiscoveringIncludes(ctx, sourcePath, targetFilePath, includes)
-			if err != nil {
+			// Unwrap error and see if it is an ExitError.
+			// Ignore ExitErrors (e.g. gcc returning
+			// non-zero status), but bail out on other
+			// errors
+			_, is_exit_error := i18n.UnwrapError(err).(*exec.ExitError)
+			if err != nil && !is_exit_error {
 				return i18n.WrapError(err)
 			}
 			include = IncludesFinderWithRegExp(ctx, stderr)

gcc_preproc_runner.go

@@ -77,7 +77,7 @@ func GCCPreprocRunnerForDiscoveringIncludes(ctx *types.Context, sourceFilePath s
 
 	stderr, err := builder_utils.ExecRecipeCollectStdErr(properties, constants.RECIPE_PREPROC_MACROS, true, verbose, verbose, logger)
 	if err != nil {
-		return "", i18n.WrapError(err)
+		return string(stderr), i18n.WrapError(err)
 	}
 
 	return string(stderr), nil

i18n/errors.go

@@ -18,3 +18,14 @@ func WrapError(err error) error {
 	}
 	return errors.Wrap(err, 0)
 }
+
+func UnwrapError(err error) error {
+	// Perhaps go-errors can do this already in later versions?
+	// See https://github.com/go-errors/errors/issues/14
+	switch e := err.(type) {
+		case *errors.Error:
+			return e.Err
+		default:
+			return err
+	}
+}