Strip comments before macro expansion in config (#193)

A bug fix that ensures comments don't interfere with macro expansion by
removing them first. This prevents unwanted comment text from appearing
in the final expanded command.

Co-authored-by: Yathiraj Bollimbala G <yathi@yStudio.localdomain>

proxy/config.go

@@ -255,6 +255,10 @@ func LoadConfigFromReader(r io.Reader) (Config, error) {
 	for _, modelId := range modelIds {
 		modelConfig := config.Models[modelId]
 
+		// Strip comments from command fields before macro expansion
+		modelConfig.Cmd = StripComments(modelConfig.Cmd)
+		modelConfig.CmdStop = StripComments(modelConfig.CmdStop)
+
 		// go through model config fields: cmd, cmdStop, proxy, checkEndPoint and replace macros with macro values
 		for macroName, macroValue := range config.Macros {
 			macroSlug := fmt.Sprintf("${%s}", macroName)
@@ -406,3 +410,16 @@ func SanitizeCommand(cmdStr string) ([]string, error) {
 
 	return args, nil
 }
+
+func StripComments(cmdStr string) string {
+	var cleanedLines []string
+	for _, line := range strings.Split(cmdStr, "\n") {
+		trimmed := strings.TrimSpace(line)
+		// Skip comment lines
+		if strings.HasPrefix(trimmed, "#") {
+			continue
+		}
+		cleanedLines = append(cleanedLines, line)
+	}
+	return strings.Join(cleanedLines, "\n")
+}

proxy/config_test.go

@@ -1,6 +1,7 @@
 package proxy
 
 import (
+	"slices"
 	"strings"
 	"testing"
 
@@ -325,3 +326,117 @@ models:
 		assert.Equal(t, []string{"temperature", "top_k", "top_p"}, sanitized)
 	}
 }
+
+func TestStripComments(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "no comments",
+			input:    "echo hello\necho world",
+			expected: "echo hello\necho world",
+		},
+		{
+			name:     "single comment line",
+			input:    "# this is a comment\necho hello",
+			expected: "echo hello",
+		},
+		{
+			name:     "multiple comment lines",
+			input:    "# comment 1\necho hello\n# comment 2\necho world",
+			expected: "echo hello\necho world",
+		},
+		{
+			name:     "comment with spaces",
+			input:    "   # indented comment\necho hello",
+			expected: "echo hello",
+		},
+		{
+			name:     "empty lines preserved",
+			input:    "echo hello\n\necho world",
+			expected: "echo hello\n\necho world",
+		},
+		{
+			name:     "only comments",
+			input:    "# comment 1\n# comment 2",
+			expected: "",
+		},
+		{
+			name:     "empty string",
+			input:    "",
+			expected: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := StripComments(tt.input)
+			if result != tt.expected {
+				t.Errorf("StripComments() = %q, expected %q", result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestConfig_MacroInCommentStrippedBeforeExpansion(t *testing.T) {
+	// Test case that reproduces the original bug where a macro in a comment
+	// would get expanded and cause the comment text to be included in the command
+	content := `
+startPort: 9990
+macros:
+  "latest-llama": >
+    /user/llama.cpp/build/bin/llama-server
+    --port ${PORT}
+
+models:
+  "test-model":
+    cmd: |
+      # ${latest-llama} is a macro that is defined above
+      ${latest-llama}
+      --model /path/to/model.gguf
+      -ngl 99
+`
+
+	config, err := LoadConfigFromReader(strings.NewReader(content))
+	assert.NoError(t, err)
+
+	// Get the sanitized command
+	sanitizedCmd, err := SanitizeCommand(config.Models["test-model"].Cmd)
+	assert.NoError(t, err)
+
+	// Join the command for easier inspection
+	cmdStr := strings.Join(sanitizedCmd, " ")
+
+	// Verify that comment text is NOT present in the final command as separate arguments
+	commentWords := []string{"is", "macro", "that", "defined", "above"}
+	for _, word := range commentWords {
+		found := slices.Contains(sanitizedCmd, word)
+		assert.False(t, found, "Comment text '%s' should not be present as a separate argument in final command", word)
+	}
+
+	// Verify that the actual command components ARE present
+	expectedParts := []string{
+		"/user/llama.cpp/build/bin/llama-server",
+		"--port",
+		"9990",
+		"--model",
+		"/path/to/model.gguf",
+		"-ngl",
+		"99",
+	}
+
+	for _, part := range expectedParts {
+		assert.Contains(t, cmdStr, part, "Expected command part '%s' not found in final command", part)
+	}
+
+	// Verify the server path appears exactly once (not duplicated due to macro expansion)
+	serverPath := "/user/llama.cpp/build/bin/llama-server"
+	count := strings.Count(cmdStr, serverPath)
+	assert.Equal(t, 1, count, "Expected exactly 1 occurrence of server path, found %d", count)
+
+	// Verify the expected final command structure
+	expectedCmd := "/user/llama.cpp/build/bin/llama-server --port 9990 --model /path/to/model.gguf -ngl 99"
+	assert.Equal(t, expectedCmd, cmdStr, "Final command does not match expected structure")
+}

proxy/process.go

@@ -212,11 +212,11 @@ func (p *Process) start() error {
 		if curState, swapErr := p.swapState(StateStarting, StateStopped); swapErr != nil {
 			p.state = StateStopped // force it into a stopped state
 			return fmt.Errorf(
-				"failed to start command and state swap failed. command error: %v, current state: %v, state swap error: %v",
-				err, curState, swapErr,
+				"failed to start command '%s' and state swap failed. command error: %v, current state: %v, state swap error: %v",
+				strings.Join(args, " "), err, curState, swapErr,
 			)
 		}
-		return fmt.Errorf("start() failed: %v", err)
+		return fmt.Errorf("start() failed for command '%s': %v", strings.Join(args, " "), err)
 	}
 
 	// Capture the exit error for later signalling

proxy/process_test.go

@@ -107,7 +107,7 @@ func TestProcess_BrokenModelConfig(t *testing.T) {
 	w = httptest.NewRecorder()
 	process.ProxyRequest(w, req)
 	assert.Equal(t, http.StatusBadGateway, w.Code)
-	assert.Contains(t, w.Body.String(), "start() failed: ")
+	assert.Contains(t, w.Body.String(), "start() failed for command 'nonexistent-command':")
 }
 
 func TestProcess_UnloadAfterTTL(t *testing.T) {