Add function for linearizing BuildStep substeps

src/build_helper/src/metrics.rs

@@ -156,12 +156,10 @@ impl BuildStep {
             child.find_by_type(r#type, result);
         }
     }
-}
-
-/// Writes build steps into a nice indented table.
-pub fn format_build_steps(root: &BuildStep) -> String {
-    use std::fmt::Write;
 
+    /// Returns a Vec with all substeps, ordered by their hierarchical order.
+    /// The first element of the tuple is the depth of a given step.
+    fn linearize_steps(&self) -> Vec<(u32, &BuildStep)> {
         let mut substeps: Vec<(u32, &BuildStep)> = Vec::new();
 
         fn visit<'a>(step: &'a BuildStep, level: u32, substeps: &mut Vec<(u32, &'a BuildStep)>) {
@@ -171,10 +169,17 @@ pub fn format_build_steps(root: &BuildStep) -> String {
             }
         }
 
-    visit(root, 0, &mut substeps);
+        visit(self, 0, &mut substeps);
+        substeps
+    }
+}
+
+/// Writes build steps into a nice indented table.
+pub fn format_build_steps(root: &BuildStep) -> String {
+    use std::fmt::Write;
 
     let mut output = String::new();
-    for (level, step) in substeps {
+    for (level, step) in root.linearize_steps() {
         let label = format!(
             "{}{}",
             ".".repeat(level as usize),