fix: Don't panic when rev-parsing ^^^ and similar (#1914)

Author: Byron

gix/src/revision/spec/parse/delegate/navigate.rs

@@ -25,7 +25,13 @@ impl delegate::Navigate for Delegate<'_> {
 
         let mut replacements = Replacements::default();
         let mut errors = Vec::new();
-        let objs = self.objs[self.idx].as_mut()?;
+        let objs = match self.objs[self.idx].as_mut() {
+            Some(objs) => objs,
+            None => {
+                self.err.push(Error::TraversalWithoutStartObject);
+                return None;
+            }
+        };
         let repo = self.repo;
 
         for obj in objs.iter() {

gix/src/revision/spec/parse/error.rs

@@ -105,7 +105,6 @@ impl Error {
     }
 
     pub(crate) fn from_errors(errors: Vec<Self>) -> Self {
-        assert!(!errors.is_empty());
         match errors.len() {
             0 => unreachable!(
                 "BUG: cannot create something from nothing, must have recorded some errors to call from_errors()"

gix/src/revision/spec/parse/types.rs

@@ -188,6 +188,8 @@ pub enum Error {
     },
     #[error(transparent)]
     Traverse(#[from] crate::revision::walk::iter::Error),
+    #[error("Tried to navigate the commit-graph without providing an anchor first")]
+    TraversalWithoutStartObject,
     #[error(transparent)]
     Walk(#[from] crate::revision::walk::Error),
     #[error("Spec does not contain a single object id")]

gix/tests/fixtures/generated-archives/make_rev_spec_parse_repos.tar

@@ -356,6 +356,7 @@ EOF
   baseline "@^{/!-B}"    # negation from branch
   baseline ":file"      # index lookup, default stage 0
   baseline ":1:file"    # stage 1
+  baseline ":5:file"    # invalid stage
   baseline ":foo"       # not found
   # parents
   baseline "a"
@@ -381,6 +382,10 @@ EOF
   baseline "b^3^2"
   baseline "a^^3^2"
 
+  # invalid
+  baseline "^^"
+  baseline "^^HEAD"
+
   baseline "@{-1}"
   baseline "@{-2}"
   baseline "@{-3}"

gix/tests/fixtures/make_rev_spec_parse_repos.sh

@@ -64,6 +64,12 @@ mod index {
             "Path \"file\" did not exist in index at stage 1. It does exist at stage 0. It exists on disk",
         );
 
+        assert_eq!(
+            parse_spec(":5:file", &repo).unwrap_err().to_string(),
+            "Path \"5:file\" did not exist in index at stage 0. It does not exist on disk",
+            "invalid stage ids are interpreted as part of the filename"
+        );
+
         assert_eq!(
             parse_spec(":foo", &repo).unwrap_err().to_string(),
             "Path \"foo\" did not exist in index at stage 0. It does not exist on disk",

gix/tests/gix/revision/spec/from_bytes/mod.rs

@@ -24,8 +24,16 @@ fn complex() -> crate::Result {
 #[test]
 fn freestanding_negation_yields_descriptive_error() -> crate::Result {
     let repo = repo("complex_graph")?;
-    let expected = "The rev-spec is malformed and misses a ref name";
-    assert_eq!(parse_spec("^", &repo).unwrap_err().to_string(), expected);
+    for revspec in ["^^", "^^HEAD"] {
+        assert_eq!(
+            parse_spec(revspec, &repo).unwrap_err().to_string(),
+            "Tried to navigate the commit-graph without providing an anchor first"
+        );
+    }
+    assert_eq!(
+        parse_spec("^", &repo).unwrap_err().to_string(),
+        "The rev-spec is malformed and misses a ref name"
+    );
     assert_eq!(
         parse_spec("^!", &repo).unwrap_err().to_string(),
         "The ref partially named \"!\" could not be found"