fix(flow): ignore transition labels in flow.mmd

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- A `flow.mmd` with a transition label (`a --> b : text`) failed with `state 'a' has no path to [*]`. steplock read `b : text` as the target state. It now ignores the label (#232)
+
 ## [0.2.2] - 2026-10-04
 
 ### Fixed

core/Cargo.toml

@@ -89,6 +89,7 @@ manual_let_else = "deny"
 items_after_statements = "deny"
 needless_pass_by_value = "deny"
 trivially_copy_pass_by_ref = "deny"
+explicit_into_iter_loop = "deny"
 
 [dependencies]
 cel-interpreter = "0.10"

core/src/flow.rs

@@ -128,7 +128,10 @@ pub fn parse_mmd(path: &str, content: &str) -> Result<FlowGraph> {
 }
 
 fn split_transition(line: &str) -> Option<(&str, &str)> {
-    line.split_once("-->")
+    let (lhs, rhs) = line.split_once("-->")?;
+    // Drop a transition label (`a --> b : text`) so the target is just `b`.
+    let rhs = rhs.split_once(':').map_or(rhs, |(target, _)| target);
+    Some((lhs, rhs))
 }
 
 fn split_label(line: &str) -> Option<(&str, &str)> {

core/src/flow_tests.rs

@@ -52,6 +52,25 @@ stateDiagram-v2
     assert!(g.is_terminal("skip_reason"));
 }
 
+#[test]
+fn ignores_transition_labels() {
+    let mmd = r"
+stateDiagram-v2
+    [*] --> tests
+    tests --> docs : yes
+    tests --> fix : no
+    fix --> docs
+    docs --> [*] : done
+    tests : Did all tests pass?
+";
+    let g = parse_mmd("test.mmd", mmd).unwrap();
+    let mut nexts = g.next_states("tests");
+    nexts.sort();
+    assert_eq!(nexts, vec!["docs", "fix"]);
+    assert!(g.is_terminal("docs"));
+    assert_eq!(g.labels["tests"], "Did all tests pass?");
+}
+
 #[test]
 fn error_on_missing_initial_state() {
     let mmd = "stateDiagram-v2\n    a --> b\n";