Change: check for non-existent dependencies

Also, rework how errors are defined

1 files changed, 36 insertions, 3 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 97ce6c3..2a46767 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -33,6 +33,8 @@ use serde_yaml;
 use serde_yaml::Value;
 use std::collections::HashMap;
 use textwrap::fill;
+use std::fmt;
+use std::error::Error;
 
 /// A step in a roadmap.
 #[derive(Clone,Debug,PartialEq)]
@@ -95,6 +97,17 @@ pub struct Roadmap {
     steps: Vec<Step>,
 }
 
+#[derive(Debug)]
+struct ParseError(String);
+
+impl fmt::Display for ParseError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "ERROR: {}", self.0)
+    }
+}
+
+impl Error for ParseError {}
+
 impl Roadmap {
     /// Create a new, empty roadmap.
     pub fn new() -> Roadmap {
@@ -102,7 +115,7 @@ impl Roadmap {
     }
 
     /// Create a new roadmap from a YAML representation.
-    pub fn from_yaml(yaml: &str) -> Result<Roadmap, Box<dyn std::error::Error>> {
+    pub fn from_yaml(yaml: &str) -> Result<Roadmap, Box<dyn Error>> {
         let mut roadmap = Roadmap::new();
         let map: HashMap<String, serde_yaml::Value> = serde_yaml::from_str(yaml)?;
 
@@ -111,6 +124,7 @@ impl Roadmap {
             roadmap.add_step(&step)?;
         }
 
+        roadmap.validate()?;
         Ok(roadmap)
     }
 
@@ -170,6 +184,25 @@ impl Roadmap {
         }
     }
 
+    // Validate that the parsed, constructed roadmap is valid.
+    fn validate(&self) -> Result<(), Box<dyn std::error::Error>> {
+        // Does every dependency exist?
+        for step in self.steps.iter() {
+            for depname in step.dependencies() {
+                match self.get_step(depname) {
+                    None => {
+                        let msg = format!("step {} depends on missing {}",
+                                          step.name(), depname);
+                        return Result::Err(Box::new(ParseError(msg.into())));
+                    }
+                    Some(_) => (),
+                }
+            }
+        }
+
+        Ok(())
+    }
+
     /// Return list of step names.
     pub fn step_names<'a>(&'a self) -> Vec<&'a str> {
         let mut names = vec![];
@@ -397,8 +430,8 @@ mod tests {
     }
 
     #[test]
-    fn parse_yaml_map_entries_not_maps() {
-        let r = Roadmap::from_yaml("foo: []");
+    fn parse_yaml_unknown_dep() {
+        let r = Roadmap::from_yaml("foo: {depends: [bar]}");
         match r {
             Ok(_) => panic!("expected a parse error"),
             _ => (),