errs: Add

3 files changed, 51 insertions, 0 deletions

diff --git a/errs/doc.go b/errs/doc.go
new file mode 100644
index 00000000..f9891334
--- /dev/null
+++ b/errs/doc.go
@@ -0,0 +1,2 @@
+// Package errs defines error types shared across furgit.
+package errs
diff --git a/errs/missing.go b/errs/missing.go
new file mode 100644
index 00000000..0630846c
--- /dev/null
+++ b/errs/missing.go
@@ -0,0 +1,25 @@
+package errs
+
+import (
+	"fmt"
+
+	"lindenii.org/go/furgit/object/id"
+)
+
+// ObjectMissingError indicates that
+// a referenced object is absent from the repository object store.
+//
+// This should only be used
+// in situations where objects are being queried recursively
+// or otherwise by some chain that the caller may not be aware of.
+//
+// Failures on direct object access
+// should instead use [lindenii.org/go/furgit/object/store.ErrObjectNotFound].
+type ObjectMissingError struct {
+	OID id.ObjectID
+}
+
+// Error implements error.
+func (e *ObjectMissingError) Error() string {
+	return fmt.Sprintf("missing object %s", e.OID)
+}
diff --git a/errs/type.go b/errs/type.go
new file mode 100644
index 00000000..f726e89b
--- /dev/null
+++ b/errs/type.go
@@ -0,0 +1,24 @@
+package errs
+
+import (
+	"fmt"
+
+	"lindenii.org/go/furgit/object/id"
+	"lindenii.org/go/furgit/object/typ"
+)
+
+// ObjectTypeError indicates that a referenced object
+// has a different type than what the operation expected.
+type ObjectTypeError struct {
+	OID  id.ObjectID
+	Got  typ.Type
+	Want typ.Type
+}
+
+// Error implements error.
+func (e *ObjectTypeError) Error() string {
+	return fmt.Sprintf(
+		"object %s has type %s, want %s",
+		e.OID, e.Got.Name(), e.Want.Name(),
+	)
+}