Represent failure with index instead of is_error in data lookup.

core/src/data_lookup/compact.rs

@@ -35,7 +35,7 @@ where
 	}
 }
 
-// If .size is equal to u32::MAX then the no commitment was generated
+// If .size is 0, and index contains items then no commitment was generated
 // because of an error that occurred.
 //
 // This is just a temporary solution that will be replaced by a more
@@ -56,17 +56,22 @@ impl CompactDataLookup {
 		Self { size, index }
 	}
 
+	pub fn is_error(&self) -> bool {
+		// For backward compatibility, case when size is u32::MAX is also supported
+		self.size == u32::MAX || (self.size == 0 && !self.index.is_empty())
+	}
+
+	// Data lookup is not valid if size is 0 and lookup index is not empty
+	fn new_error() -> Self {
+		Self {
+			size: 0,
+			index: [DataLookupItem::new(AppId(0), 0)].to_vec(),
+		}
+	}
+
 	pub fn from_data_lookup(lookup: &DataLookup) -> Self {
-		if lookup.is_error {
-			// Data lookup is not valid if size is 0 and lookup index is not empty
-			return CompactDataLookup {
-				size: 0,
-				index: [DataLookupItem {
-					app_id: AppId(0),
-					start: 0,
-				}]
-				.to_vec(),
-			};
+		if lookup.is_error() {
+			return Self::new_error();
 		}
 
 		let index = lookup

core/src/data_lookup/mod.rs

@@ -33,7 +33,6 @@
 )]
 pub struct DataLookup {
 	pub(crate) index: Vec<(AppId, DataLookupRange)>,
-	pub(crate) is_error: bool,
 }
 
 impl DataLookup {
@@ -45,6 +44,10 @@
 		self.len() == 0
 	}
 
+	pub fn is_error(&self) -> bool {
+		self.is_empty() && !self.index.is_empty()
+	}
+
 	pub fn range_of(&self, app_id: AppId) -> Option<DataLookupRange> {
 		self.index
 			.iter()
@@ -113,25 +116,18 @@
 			})
 			.collect::<Result<_, _>>()?;
 
-		Ok(Self {
-			index,
-			is_error: false,
-		})
+		Ok(Self { index })
 	}
 
 	/// This function is used a block contains no data submissions.
 	pub fn new_empty() -> Self {
-		Self {
-			index: Vec::new(),
-			is_error: false,
-		}
+		Self { index: Vec::new() }
 	}
 
 	/// This function is only used when something has gone wrong during header extension building
 	pub fn new_error() -> Self {
 		Self {
-			index: Vec::new(),
-			is_error: true,
+			index: vec![(AppId(0), 0..0)],
 		}
 	}
 }
@@ -140,7 +136,7 @@
 	type Error = Error;
 
 	fn try_from(compacted: CompactDataLookup) -> Result<Self, Self::Error> {
-		if compacted.size == u32::MAX {
+		if compacted.is_error() {
 			return Ok(DataLookup::new_error());
 		}
 
@@ -165,10 +161,7 @@
 			index.push((prev_id, offset..compacted.size));
 		}
 
-		let lookup = DataLookup {
-			index,
-			is_error: false,
-		};
+		let lookup = DataLookup { index };
 		ensure!(lookup.len() == compacted.size, Error::DataNotSorted);
 
 		Ok(lookup)
@@ -181,7 +174,7 @@
 impl Encode for DataLookup {
 	/// Encodes as a `compact::DataLookup`.
 	fn encode(&self) -> Vec<u8> {
 		let compacted: CompactDataLookup = CompactDataLookup::from_data_lookup(&self);
 		compacted.encode()
 	}
 }