go/doltcore/{merge,sqle}: populate description column for dolt_schema_conflicts table

go/libraries/doltcore/merge/merge_schema.go

@@ -38,18 +38,6 @@ const (
 	DeletedCheckCollision
 )
 
-// todo: link to docs explaining how to resolve schema conflicts.
-func SchemaConflictErr(cc ...SchemaConflict) error {
-	var sb strings.Builder
-	sb.WriteString("merge aborted: schema conflict found for tables: \n")
-	for i := range cc {
-		sb.WriteRune('\t')
-		sb.WriteString(cc[i].TableName)
-		sb.WriteRune('\n')
-	}
-	return errors.New(sb.String())
-}
-
 type SchemaConflict struct {
 	TableName    string
 	ColConflicts []ColConflict
@@ -63,21 +51,37 @@ func (sc SchemaConflict) Count() int {
 	return len(sc.ColConflicts) + len(sc.IdxConflicts) + len(sc.ChkConflicts)
 }
 
+// String implements fmt.Stringer. This method is used to
+// display schema conflicts on schema conflict read paths.
+func (sc SchemaConflict) String() string {
+	return strings.Join(sc.messages(), "\n")
+}
+
+// Error implements error. This error will be returned to the
+// user if merge is configured to error upon schema conflicts.
+// todo: link to docs explaining how to resolve schema conflicts.
 func (sc SchemaConflict) Error() string {
+	template := "merge aborted: schema conflict found for table %s \n" +
+		" please resolve schema conflicts before merging: %s"
 	var b strings.Builder
-	b.WriteString("merge aborted: schema conflict found for table ")
-	b.WriteString(sc.TableName)
-	b.WriteString("\n please resolve schema conflicts before merging")
+	for _, m := range sc.messages() {
+		b.WriteString("\n\t")
+		b.WriteString(m)
+	}
+	return fmt.Sprintf(template, sc.TableName, b.String())
+}
+
+func (sc SchemaConflict) messages() (mm []string) {
 	for _, c := range sc.ColConflicts {
-		b.WriteString(fmt.Sprintf("\t%s\n", c.String()))
+		mm = append(mm, c.String())
 	}
 	for _, c := range sc.IdxConflicts {
-		b.WriteString(fmt.Sprintf("\t%s\n", c.String()))
+		mm = append(mm, c.String())
 	}
 	for _, c := range sc.ChkConflicts {
-		b.WriteString(fmt.Sprintf("\t%s\n", c.String()))
+		mm = append(mm, c.String())
 	}
-	return b.String()
+	return
 }
 
 type ColConflict struct {

go/libraries/doltcore/sqle/dtables/schema_conflicts_table.go

@@ -24,9 +24,11 @@ import (
 
 	"github.com/dolthub/dolt/go/libraries/doltcore/diff"
 	"github.com/dolthub/dolt/go/libraries/doltcore/doltdb"
+	"github.com/dolthub/dolt/go/libraries/doltcore/merge"
 	"github.com/dolthub/dolt/go/libraries/doltcore/schema"
 	"github.com/dolthub/dolt/go/libraries/doltcore/sqle/dsess"
 	"github.com/dolthub/dolt/go/libraries/doltcore/sqle/sqlutil"
+	noms "github.com/dolthub/dolt/go/store/types"
 )
 
 var _ sql.Table = (*SchemaConflictsTable)(nil)
@@ -148,8 +150,20 @@ type schemaConflict struct {
 	description string
 }
 
-func newSchemaConflict(ctx context.Context, table string, br *doltdb.RootValue, c doltdb.SchemaConflict) (schemaConflict, error) {
-	base, err := getCreateTableStatementFromRoot(ctx, table, br)
+func newSchemaConflict(ctx context.Context, table string, baseRoot *doltdb.RootValue, c doltdb.SchemaConflict) (schemaConflict, error) {
+	bs, err := baseRoot.GetAllSchemas(ctx)
+	if err != nil {
+		return schemaConflict{}, err
+	}
+	baseSch := bs[table]
+
+	fkc, err := baseRoot.GetForeignKeyCollection(ctx)
+	if err != nil {
+		return schemaConflict{}, err
+	}
+	baseFKs, _ := fkc.KeysForTable(table)
+
+	base, err := getCreateTableStatement(table, baseSch, baseFKs, bs)
 	if err != nil {
 		return schemaConflict{}, err
 	}
@@ -164,30 +178,20 @@ func newSchemaConflict(ctx context.Context, table string, br *doltdb.RootValue,
 		return schemaConflict{}, err
 	}
 
+	desc, err := getSchemaConflictDescription(ctx, table, baseSch, c.ToSch, c.FromSch)
+	if err != nil {
+		return schemaConflict{}, err
+	}
+
 	return schemaConflict{
-		table:    table,
-		baseSch:  base,
-		ourSch:   ours,
-		theirSch: theirs,
+		table:       table,
+		baseSch:     base,
+		ourSch:      ours,
+		theirSch:    theirs,
+		description: desc,
 	}, nil
 }
 
-func getCreateTableStatementFromRoot(ctx context.Context, table string, root *doltdb.RootValue) (string, error) {
-	schemas, err := root.GetAllSchemas(ctx)
-	if err != nil {
-		return "", err
-	}
-	sch := schemas[table]
-
-	fkc, err := root.GetForeignKeyCollection(ctx)
-	if err != nil {
-		return "", err
-	}
-	fks, _ := fkc.KeysForTable(table)
-
-	return getCreateTableStatement(table, sch, fks, schemas)
-}
-
 func getCreateTableStatement(table string, sch schema.Schema, fks []doltdb.ForeignKey, parents map[string]schema.Schema) (string, error) {
 	pkSch, err := sqlutil.FromDoltSchema(table, sch)
 	if err != nil {
@@ -196,6 +200,15 @@ func getCreateTableStatement(table string, sch schema.Schema, fks []doltdb.Forei
 	return diff.GenerateCreateTableStatement(table, sch, pkSch, fks, parents)
 }
 
+func getSchemaConflictDescription(ctx context.Context, table string, base, ours, theirs schema.Schema) (string, error) {
+	nbf := noms.Format_Default
+	_, conflict, err := merge.SchemaMerge(ctx, nbf, ours, theirs, base, table)
+	if err != nil {
+		return "", err
+	}
+	return conflict.String(), nil
+}
+
 type schemaConflictsIter struct {
 	conflicts   []schemaConflict
 	baseSchemas map[string]schema.Schema

go/libraries/doltcore/sqle/enginetest/dolt_queries_merge.go

@@ -2906,7 +2906,7 @@ var SchemaConflictScripts = []queries.ScriptTest{
 					"CREATE TABLE `t` (\n  `pk` int NOT NULL,\n  `c0` varchar(20),\n  PRIMARY KEY (`pk`)\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin;",
 					"CREATE TABLE `t` (\n  `pk` int NOT NULL,\n  `c0` datetime(6),\n  PRIMARY KEY (`pk`)\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin;",
 					"CREATE TABLE `t` (\n  `pk` int NOT NULL,\n  `c0` int,\n  PRIMARY KEY (`pk`)\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin;",
-					"",
+					"different column definitions for our column c0 and their column c0",
 				}},
 			},
 			{