Allow passing YAML directly instead of writing to a file

Author: joecorall

README.md

@@ -107,6 +107,7 @@ PPB also supports these environment variables for runtime configuration:
 
 | Variable                         | Description                                  | Default                  |
 |----------------------------------|----------------------------------------------|--------------------------|
+| `PPB_YAML`                       | YAML configuration content (takes priority)  | -                        |
 | `PPB_CONFIG_PATH`                | Path to YAML configuration file              | /app/ppb.yaml            |
 | `LOG_LEVEL`                      | Log level (`DEBUG`, `INFO`, `WARN`, `ERROR`) | `INFO`                   |
 | `GOOGLE_APPLICATION_CREDENTIALS` | Path to service account JSON file            | Uses default credentials |

pkg/config/config.go

@@ -52,15 +52,27 @@ func (i *IPNet) UnmarshalYAML(value *yaml.Node) error {
 }
 
 func LoadConfig() (*Config, error) {
-	filename := os.Getenv("PPB_CONFIG_PATH")
-	if filename == "" {
-		filename = "ppb.yaml"
-	}
-	slog.Debug("Loading config", "filename", filename)
-	data, err := os.ReadFile(filename)
-	if err != nil {
-		return nil, err
+	var data []byte
+	var err error
+
+	// Check for PPB_YAML environment variable first (highest priority)
+	yamlContent := os.Getenv("PPB_YAML")
+	if yamlContent != "" {
+		slog.Debug("Loading config from PPB_YAML environment variable")
+		data = []byte(yamlContent)
+	} else {
+		// Fall back to file-based configuration
+		filename := os.Getenv("PPB_CONFIG_PATH")
+		if filename == "" {
+			filename = "ppb.yaml"
+		}
+		slog.Debug("Loading config", "filename", filename)
+		data, err = os.ReadFile(filename)
+		if err != nil {
+			return nil, err
+		}
 	}
+
 	expandedYaml := os.ExpandEnv(string(data))
 
 	var config Config

pkg/config/config_test.go

@@ -3,6 +3,7 @@ package config
 import (
 	"net"
 	"net/http"
+	"os"
 	"testing"
 
 	yaml "gopkg.in/yaml.v3"
@@ -320,6 +321,97 @@ func TestConfig_setProxyTimeoutDefaults(t *testing.T) {
 	}
 }
 
+func TestLoadConfig_WithPPB_YAML(t *testing.T) {
+	// Save original env vars
+	originalYAML := os.Getenv("PPB_YAML")
+	originalPath := os.Getenv("PPB_CONFIG_PATH")
+	defer func() {
+		os.Setenv("PPB_YAML", originalYAML)
+		os.Setenv("PPB_CONFIG_PATH", originalPath)
+	}()
+
+	tests := []struct {
+		name        string
+		yamlContent string
+		wantErr     bool
+		wantType    string
+	}{
+		{
+			name: "valid YAML via PPB_YAML",
+			yamlContent: `type: google_compute_engine
+scheme: https
+port: 443
+allowedIps:
+  - 0.0.0.0/0
+machineMetadata:
+  project_id: test-project
+  zone: us-central1-a
+  name: test-instance`,
+			wantErr:  false,
+			wantType: "google_compute_engine",
+		},
+		{
+			name:        "invalid YAML via PPB_YAML",
+			yamlContent: "invalid: yaml: content: [[[",
+			wantErr:     true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			os.Setenv("PPB_YAML", tt.yamlContent)
+			os.Unsetenv("PPB_CONFIG_PATH")
+
+			config, err := LoadConfig()
+
+			if (err != nil) != tt.wantErr {
+				t.Errorf("LoadConfig() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+
+			if !tt.wantErr {
+				if config.Type != tt.wantType {
+					t.Errorf("LoadConfig() Type = %v, want %v", config.Type, tt.wantType)
+				}
+			}
+		})
+	}
+}
+
+func TestLoadConfig_PriorityOrder(t *testing.T) {
+	// Save original env vars
+	originalYAML := os.Getenv("PPB_YAML")
+	originalPath := os.Getenv("PPB_CONFIG_PATH")
+	defer func() {
+		os.Setenv("PPB_YAML", originalYAML)
+		os.Setenv("PPB_CONFIG_PATH", originalPath)
+	}()
+
+	yamlContent := `type: google_compute_engine
+scheme: https
+port: 443
+allowedIps:
+  - 0.0.0.0/0
+machineMetadata:
+  project_id: from-env-var
+  zone: us-central1-a
+  name: test-instance`
+
+	// Test that PPB_YAML takes priority over PPB_CONFIG_PATH
+	os.Setenv("PPB_YAML", yamlContent)
+	os.Setenv("PPB_CONFIG_PATH", "/nonexistent/file.yaml")
+
+	config, err := LoadConfig()
+	if err != nil {
+		t.Errorf("LoadConfig() should succeed with PPB_YAML even if PPB_CONFIG_PATH is invalid, error = %v", err)
+		return
+	}
+
+	if config.Machine.ProjectId != "from-env-var" {
+		t.Errorf("LoadConfig() should load from PPB_YAML, got project_id = %v, want from-env-var", config.Machine.ProjectId)
+	}
+}
+
 func TestProxyTimeouts_UnmarshalYAML(t *testing.T) {
 	tests := []struct {
 		name     string