From dcbcbd9457d4bd4d21bcf8dbcc9e416fff463d92 Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Fri, 20 Mar 2020 08:46:16 +0200
Subject: Change: make error message for wrong number of goals more helpful

---
 legend.yaml |  5 +++++
 src/map.rs  | 17 ++++++++++++++---
 src/step.rs |  7 +++++++
 3 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/legend.yaml b/legend.yaml
index fc17ba8..951d369 100644
--- a/legend.yaml
+++ b/legend.yaml
@@ -1,3 +1,8 @@
+goal2: {}
+goal3: {}
+goal4: {}
+goal5: {}
+
 goal:
   label: |
     This is the end goal:
diff --git a/src/map.rs b/src/map.rs
index 77b2feb..c1294bf 100644
--- a/src/map.rs
+++ b/src/map.rs
@@ -27,7 +27,10 @@ impl Roadmap {
 
     // Find steps that nothing depends on.
     fn goals(&self) -> Vec<&Step> {
-        self.steps.iter().filter(|step| self.is_goal(step)).collect()
+        self.steps
+            .iter()
+            .filter(|step| self.is_goal(step))
+            .collect()
     }
 
     /// Count number of steps that nothing depends on.
@@ -125,10 +128,18 @@ impl Roadmap {
     // Validate that the parsed, constructed roadmap is valid.
     pub fn validate(&self) -> RoadmapResult<()> {
         // Is there exactly one goal?
-        match self.count_goals() {
+        let goals = self.goals();
+        let n = goals.len();
+        match n {
             0 => return Err(format!("the roadmap doesn't have a goal").into()),
             1 => (),
-            _ => return Err(format!("must have exactly one goal for roadmap").into()),
+            _ => {
+                let mut names: Vec<&str> = goals.iter().map(|s| s.name()).collect();
+                names.sort();
+                let names = names.join(", ");
+                let msg = format!("only one goal allowed, found {}: {}", n, names);
+                return Err(msg.into());
+            }
         }
 
         // Does every dependency exist?
diff --git a/src/step.rs b/src/step.rs
index 1ed495b..92b8eec 100644
--- a/src/step.rs
+++ b/src/step.rs
@@ -1,4 +1,5 @@
 use super::Status;
+use std::fmt;
 
 /// A roadmap step.
 ///
@@ -62,6 +63,12 @@ impl Step {
     }
 }
 
+impl fmt::Display for Step {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.name)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::{Status, Step};
-- 
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