fix: address PR review comments (#3, #4, #5)

- --help now always takes precedence over --doc regardless of arg order
- Updated AsMain doc comment to document all invocation modes
- Removed no-op strings.TrimPrefix in test assertion

Signed-off-by: Fiachra Corcoran <fiachra.corcoran@est.tech>

Author: efiacor

go/fn/run.go

@@ -42,12 +42,20 @@ func WithDocs(readme []byte, meta []byte) Option {
 	}
 }
 
-// AsMain evaluates the ResourceList from STDIN to STDOUT.
+// AsMain evaluates a KRM function. By default it reads a ResourceList from
+// STDIN, processes it, and writes the result to STDOUT.
+//
 // `input` can be
 // - a `ResourceListProcessor` which implements `Process` method
 // - a function `Runner` which implements `Run` method
 //
-// Options configure additional behavior such as --help and --doc support
+// Invocation modes (checked in this order):
+//   - --help: prints human-readable documentation to STDOUT and returns nil.
+//   - --doc: prints machine-readable JSON documentation to STDOUT and returns nil.
+//   - positional file args: reads KRM resources from files instead of STDIN.
+//   - no args: reads ResourceList from STDIN (default behavior).
+//
+// Options configure additional behavior such as documentation support
 // via WithDocs. Existing callers with no options continue to work unchanged.
 func AsMain(input any, opts ...Option) error {
 	// Apply options to build configuration.
@@ -57,10 +65,13 @@ func AsMain(input any, opts ...Option) error {
 	}
 
 	// Check for --help and --doc flags before reading STDIN.
+	// --help always takes precedence over --doc regardless of argument order.
 	for _, arg := range os.Args[1:] {
 		if arg == "--help" {
 			return handleHelp(&cfg)
 		}
+	}
+	for _, arg := range os.Args[1:] {
 		if arg == "--doc" {
 			return handleDoc(&cfg)
 		}

go/fn/run_filemode_test.go

@@ -17,7 +17,6 @@ package fn
 import (
 	"os"
 	"path/filepath"
-	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -423,6 +422,6 @@ func TestFileMode_NonExistentAmongValid(t *testing.T) {
 		err := AsMain(noopProcessor)
 		require.Error(t, err)
 		assert.Contains(t, err.Error(), "file not found")
-		assert.Contains(t, err.Error(), strings.TrimPrefix(nonExistent, ""))
+		assert.Contains(t, err.Error(), nonExistent)
 	})
 }