Merge pull request #1922 from dolthub/andy/read-empty-conflicts

[no-release-notes] Andy/read empty conflicts

go/libraries/doltcore/doltdb/table.go

@@ -154,23 +154,19 @@ func (t *Table) SetConflicts(ctx context.Context, schemas Conflict, conflictData
 
 func (t *Table) GetConflicts(ctx context.Context) (Conflict, types.Map, error) {
 	schemasVal, ok, err := t.tableStruct.MaybeGet(conflictSchemasKey)
-
 	if err != nil {
 		return Conflict{}, types.EmptyMap, err
 	}
-
 	if !ok {
 		return Conflict{}, types.EmptyMap, ErrNoConflicts
 	}
 
 	schemas, err := ConflictFromTuple(schemasVal.(types.Tuple))
-
 	if err != nil {
 		return Conflict{}, types.EmptyMap, err
 	}
 
 	conflictsVal, _, err := t.tableStruct.MaybeGet(conflictsKey)
-
 	if err != nil {
 		return Conflict{}, types.EmptyMap, err
 	}

go/libraries/doltcore/merge/conflict_source.go

@@ -47,7 +47,10 @@ type ConflictReader struct {
 // NewConflictReader returns a new conflict reader for a given table
 func NewConflictReader(ctx context.Context, tbl *doltdb.Table) (*ConflictReader, error) {
 	base, sch, mergeSch, err := tbl.GetConflictSchemas(ctx)
-
+	if err == doltdb.ErrNoConflicts {
+		base, err = tbl.GetSchema(ctx)
+		sch, mergeSch = base, base
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -63,19 +66,19 @@ func NewConflictReader(ctx context.Context, tbl *doltdb.Table) (*ConflictReader,
 			theirsStr: func(colName string) string { return theirsStr + "_" + colName },
 		},
 	)
-
 	if err != nil {
 		return nil, err
 	}
 
 	_, confData, err := tbl.GetConflicts(ctx)
-
+	if err == doltdb.ErrNoConflicts {
+		confData, err = types.NewMap(ctx, tbl.ValueReadWriter())
+	}
 	if err != nil {
 		return nil, err
 	}
 
 	confItr, err := confData.Iterator(ctx)
-
 	if err != nil {
 		return nil, err
 	}

integration-tests/bats/sql-conflicts.bats

@@ -30,6 +30,10 @@ teardown() {
 	teardown_common
 }
 
+@test "sql-conflicts: read from empty table" {
+    dolt sql -q "SELECT * FROM dolt_conflicts_empty"
+}
+
 @test "sql-conflicts: add conflict" {
   dolt branch feature_branch master
   dolt SQL -q "INSERT INTO one_pk (pk1,c1,c2) VALUES (0,0,0)"