Improve error messages for PostCSS etc.

Fixes #9730

4 files changed, 26 insertions, 5 deletions

diff --git a/resources/resource_transformers/babel/babel.go b/resources/resource_transformers/babel/babel.go
index 5f8fcb00f..2999d73cb 100644
--- a/resources/resource_transformers/babel/babel.go
+++ b/resources/resource_transformers/babel/babel.go
@@ -181,7 +181,7 @@ func (t *babelTransformation) Transform(ctx *resources.ResourceTransformationCtx
 	if err != nil {
 		if hexec.IsNotFound(err) {
 			// This may be on a CI server etc. Will fall back to pre-built assets.
-			return herrors.ErrFeatureNotAvailable
+			return &herrors.FeatureNotAvailableError{Cause: err}
 		}
 		return err
 	}
@@ -200,7 +200,7 @@ func (t *babelTransformation) Transform(ctx *resources.ResourceTransformationCtx
 	err = cmd.Run()
 	if err != nil {
 		if hexec.IsNotFound(err) {
-			return herrors.ErrFeatureNotAvailable
+			return &herrors.FeatureNotAvailableError{Cause: err}
 		}
 		return fmt.Errorf(errBuf.String()+": %w", err)
 	}
diff --git a/resources/resource_transformers/postcss/integration_test.go b/resources/resource_transformers/postcss/integration_test.go
index c920fe17d..74aaa2661 100644
--- a/resources/resource_transformers/postcss/integration_test.go
+++ b/resources/resource_transformers/postcss/integration_test.go
@@ -168,6 +168,25 @@ func TestTransformPostCSSError(t *testing.T) {
 
 }
 
+func TestTransformPostCSSNotInstalledError(t *testing.T) {
+	if !htesting.IsCI() {
+		t.Skip("Skip long running test when running locally")
+	}
+
+	c := qt.New(t)
+
+	s, err := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{
+			T:           c,
+			NeedsOsFS:   true,
+			TxtarString: postCSSIntegrationTestFiles,
+		}).BuildE()
+
+	s.AssertIsFileError(err)
+	c.Assert(err.Error(), qt.Contains, `binary with name "npx" not found`)
+
+}
+
 // #9895
 func TestTransformPostCSSImportError(t *testing.T) {
 	if !htesting.IsCI() {
diff --git a/resources/resource_transformers/postcss/postcss.go b/resources/resource_transformers/postcss/postcss.go
index 083607246..a65fa3783 100644
--- a/resources/resource_transformers/postcss/postcss.go
+++ b/resources/resource_transformers/postcss/postcss.go
@@ -205,7 +205,7 @@ func (t *postcssTransformation) Transform(ctx *resources.ResourceTransformationC
 	if err != nil {
 		if hexec.IsNotFound(err) {
 			// This may be on a CI server etc. Will fall back to pre-built assets.
-			return herrors.ErrFeatureNotAvailable
+			return &herrors.FeatureNotAvailableError{Cause: err}
 		}
 		return err
 	}
@@ -240,7 +240,9 @@ func (t *postcssTransformation) Transform(ctx *resources.ResourceTransformationC
 	err = cmd.Run()
 	if err != nil {
 		if hexec.IsNotFound(err) {
-			return herrors.ErrFeatureNotAvailable
+			return &herrors.FeatureNotAvailableError{
+				Cause: err,
+			}
 		}
 		return imp.toFileError(errBuf.String())
 	}
diff --git a/resources/transform.go b/resources/transform.go
index 9e5b57625..eb7d8fb0b 100644
--- a/resources/transform.go
+++ b/resources/transform.go
@@ -449,7 +449,7 @@ func (r *resourceAdapter) transform(publish, setContent bool) error {
 		newErr := func(err error) error {
 			msg := fmt.Sprintf("%s: failed to transform %q (%s)", strings.ToUpper(tr.Key().Name), tctx.InPath, tctx.InMediaType.Type)
 
-			if err == herrors.ErrFeatureNotAvailable {
+			if herrors.IsFeatureNotAvailableError(err) {
 				var errMsg string
 				if tr.Key().Name == "postcss" {
 					// This transformation is not available in this