fix: Support reading database connection string from environment variable

internal/cli/commands.go

@@ -20,6 +20,16 @@ var (
 	errInvalidTimeFormat        = errors.New("time format may not be empty")
 )
 
+// databaseFromEnv reads the database connection string from the specified environment variable.
+// Returns the value if set, or an error if the environment variable is not set or empty.
+func databaseFromEnv(envName string) (string, error) {
+	val := os.Getenv(envName)
+	if val == "" {
+		return "", fmt.Errorf("environment variable %s is not set or empty", envName)
+	}
+	return val, nil
+}
+
 func nextSeqVersion(matches []string, seqDigits int) (string, error) {
 	if seqDigits <= 0 {
 		return "", errInvalidSequenceWidth

internal/cli/commands_test.go

@@ -253,6 +253,47 @@
 	}
 }
 
+func TestDatabaseFromEnv(t *testing.T) {
+	cases := []struct {
+		name           string
+		envName        string
+		envValue       string
+		setEnv         bool
+		expectedResult string
+		expectedErrStr string
+	}{
+		{"valid env var", "TEST_DB_URL", "postgres://localhost:5432/test", true, "postgres://localhost:5432/test", ""},
+		{"empty env var", "TEST_DB_URL_EMPTY", "", true, "", "environment variable TEST_DB_URL_EMPTY is not set or empty"},
+		{"unset env var", "TEST_DB_URL_UNSET", "", false, "", "environment variable TEST_DB_URL_UNSET is not set or empty"},
+	}
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if c.setEnv {
+				os.Setenv(c.envName, c.envValue)
+				defer os.Unsetenv(c.envName)
+			}
+
+			result, err := databaseFromEnv(c.envName)
+
+			if c.expectedErrStr != "" {
+				if err == nil {
+					t.Errorf("Expected error: %s but got nil", c.expectedErrStr)
+				} else if err.Error() != c.expectedErrStr {
+					t.Errorf("Expected error: %s but got: %s", c.expectedErrStr, err.Error())
+				}
+			} else {
+				if err != nil {
+					t.Errorf("Unexpected error: %s", err.Error())
+				}
+				if result != c.expectedResult {
+					t.Errorf("Expected result: %s but got: %s", c.expectedResult, result)
+				}
+			}
+		})
+	}
+}
+
 func TestNumDownFromArgs(t *testing.T) {
 	cases := []struct {
 		name                string

internal/cli/main.go

@@ -68,6 +68,7 @@ func Main(version string) {
 	pathPtr := flag.String("path", "", "")
 	databasePtr := flag.String("database", "", "")
 	sourcePtr := flag.String("source", "", "")
+	envPtr := flag.String("env", "", "")
 
 	flag.Usage = func() {
 		fmt.Fprintf(os.Stderr,
@@ -78,6 +79,7 @@ Options:
   -source          Location of the migrations (driver://url)
   -path            Shorthand for -source=file://path
   -database        Run migrations against this database (driver://url)
+  -env             Read database connection string from environment variable
   -prefetch N      Number of migrations to load in advance before executing (default 10)
   -lock-timeout N  Allow N seconds to acquire database lock (default 15)
   -verbose         Print verbose logging
@@ -119,6 +121,15 @@ Database drivers: `+strings.Join(database.List(), ", ")+"\n", createUsage, gotoU
 		*sourcePtr = fmt.Sprintf("file://%v", *pathPtr)
 	}
 
+	// read database connection string from environment variable if -env is given
+	if *envPtr != "" {
+		dbFromEnv, err := databaseFromEnv(*envPtr)
+		if err != nil {
+			log.fatalErr(err)
+		}
+		*databasePtr = dbFromEnv
+	}
+
 	// initialize migrate
 	// don't catch migraterErr here and let each command decide
 	// how it wants to handle the error