Fix merge issues and more tests

go/cmd/dolt/commands/diff.go

@@ -17,7 +17,7 @@ package commands
 import (
 	"context"
 	"fmt"
-	"reflect"
+	"io"
 	"sort"
 	"strings"
 
@@ -444,13 +444,12 @@ func newSqlEngine(ctx context.Context, dEnv *env.DoltEnv) (*engine.SqlEngine, er
 		ctx,
 		mrEnv,
 		engine.FormatCsv,
-		dbName,
-		false,
-		"",
-		"",
-		"root",
-		"",
-		false,
+		&engine.SqlEngineConfig{
+			InitialDb:    dbName,
+			IsReadOnly:   false,
+			ServerUser:   "root",
+			Autocommit:   false,
+		},
 	)
 }
 

go/libraries/doltcore/sqle/dtables/diff_table.go

@@ -526,18 +526,25 @@ func GetDiffTableSchemaAndJoiner(format *types.NomsBinFormat, fromSch, toSch sch
 			return nil, nil, err
 		}
 	} else {
-		colCollection := toSch.GetAllCols()
-		colCollection = colCollection.Append(
-			schema.NewColumn("commit", schema.DiffCommitTag, types.StringKind, false),
-			schema.NewColumn("commit_date", schema.DiffCommitDateTag, types.TimestampKind, false))
-		toSch = schema.MustSchemaFromCols(colCollection)
 
-		colCollection = fromSch.GetAllCols()
+		colCollection := schema.NewColCollection()
+		if fromSch != nil {
+			colCollection = fromSch.GetAllCols()
+		}
 		colCollection = colCollection.Append(
 			schema.NewColumn("commit", schema.DiffCommitTag, types.StringKind, false),
 			schema.NewColumn("commit_date", schema.DiffCommitDateTag, types.TimestampKind, false))
 		fromSch = schema.MustSchemaFromCols(colCollection)
 
+		colCollection = schema.NewColCollection()
+		if toSch != nil {
+			colCollection = toSch.GetAllCols()
+		}
+		colCollection = colCollection.Append(
+			schema.NewColumn("commit", schema.DiffCommitTag, types.StringKind, false),
+			schema.NewColumn("commit_date", schema.DiffCommitDateTag, types.TimestampKind, false))
+		toSch = schema.MustSchemaFromCols(colCollection)
+
 		j, err = rowconv.NewJoiner(
 			[]rowconv.NamedSchema{{Name: diff.To, Sch: toSch}, {Name: diff.From, Sch: fromSch}},
 			map[string]rowconv.ColNamingFunc{

go/libraries/doltcore/sqle/enginetest/dolt_queries.go

@@ -2992,12 +2992,20 @@ var DiffTableFunctionScriptTests = []queries.ScriptTest{
 		Name:         "new table",
 		SetUpScript:  []string{
 			"create table t1 (a int primary key, b int)",
-			"insert into t1 values (1,1)",
+			"insert into t1 values (1,2)",
 		},
-		Assertions:   []queries.ScriptTestAssertion{
+		Assertions: []queries.ScriptTestAssertion{
 			{
-				Query:                           "select * from dolt_diff",
-				Expected:                        nil,
+				Query:    "select to_a, to_b, from_commit, to_commit, diff_type from dolt_diff('t1', 'HEAD', 'WORKING')",
+				Expected: []sql.Row{{1, 2, "HEAD", "WORKING", "added"}},
+			},
+			{
+				Query:    "select to_a, from_b, from_commit, to_commit, diff_type from dolt_diff('t1', 'HEAD', 'WORKING')",
+				ExpectedErr: sql.ErrColumnNotFound,
+			},
+			{
+				Query:    "select from_a, from_b, from_commit, to_commit, diff_type from dolt_diff('t1', 'WORKING', 'HEAD')",
+				Expected: []sql.Row{{1, 2, "WORKING", "HEAD", "removed"}},
 			},
 		},
 	},