More tidying up

go/libraries/doltcore/merge/merge_prolly_rows.go

@@ -422,14 +422,12 @@ func (cv checkValidator) validateDiff(ctx *sql.Context, diff tree.ThreeWayDiff)
 			valueTuple = diff.Merged
 			valueDesc = cv.tableMerger.leftSch.GetValueDescriptor()
 		case tree.DiffOpDivergentDeleteConflict, tree.DiffOpDivergentModifyConflict:
-			// TODO: Add a test case to trigger this... would this even get this far?
-			return 0, fmt.Errorf("check constraint validation not supported for divergent conflicts")
+			// Don't bother validating divergent conflicts, just let them get reported as conflicts
+			return 0, nil
 		}
 
-		// TODO: Do we need to honor column defaults here? Seems like it?
-		// TEST: A new column with a column default is added, and the column default value causes a check violation
-		//       (check must be just added on one side of the merge to trigger this)
 		newTuple := valueTuple
+		// TODO: Why are our tests working without this?!
 		if false {
 			// TODO: If we're using diff.Merged, then that means we don't need to do any remapping, right?
 			// TODO: This right mapping needs to be different, right? for each diff op type?
@@ -448,9 +446,8 @@ func (cv checkValidator) validateDiff(ctx *sql.Context, diff tree.ThreeWayDiff)
 		}
 
 		if result == nil || result == true {
-			// If a check constraint returns NULL (aka UNKNOWN) or TRUE, then the check constraint is fulfilled
+			// If a check constraint returns NULL or TRUE, then the check constraint is fulfilled
 			// https://dev.mysql.com/doc/refman/8.0/en/create-table-check-constraints.html
-			// TODO: Add a test case for CHECK(NULL = NULL) –something that will always return NULL
 			continue
 		} else if result == false {
 			conflictCount++

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

@@ -4381,11 +4381,73 @@ var ThreeWayMergeWithSchemaChangeTestScripts = []MergeScriptTest{
 			},
 		},
 	},
+	{
+		Name: "check constraint violation - divergent edits",
+		AncSetUpScript: []string{
+			"set autocommit = 0;",
+			"CREATE table t (pk int primary key, col1 varchar(100) default ('hello'));",
+			"INSERT into t values (1, 'hi');",
+			"alter table t add index idx1 (col1);",
+		},
+		RightSetUpScript: []string{
+			"alter table t add constraint CHECK (col1 != concat('he', 'llo'))",
+			"update t set col1 = 'bye' where pk=1;",
+		},
+		LeftSetUpScript: []string{
+			"update t set col1 = 'adios' where pk=1;",
+		},
+		Assertions: []queries.ScriptTestAssertion{
+			{
+				Query:    "call dolt_merge('right');",
+				Expected: []sql.Row{{0, 0x1}},
+			},
+		},
+	},
+	{
+		Name: "check constraint violation - check is always NULL",
+		AncSetUpScript: []string{
+			"CREATE table t (pk int primary key, col1 varchar(100) default ('hello'));",
+			"INSERT into t values (1, 'hi');",
+			"alter table t add index idx1 (col1);",
+		},
+		RightSetUpScript: []string{
+			"alter table t add constraint CHECK (NULL = NULL)",
+		},
+		LeftSetUpScript: []string{
+			"insert into t values (2, DEFAULT);",
+		},
+		Assertions: []queries.ScriptTestAssertion{
+			{
+				Query:    "call dolt_merge('right');",
+				Expected: []sql.Row{{0, 0x0}},
+			},
+		},
+	},
+	{
+		Name: "check constraint violation - check is always false",
+		AncSetUpScript: []string{
+			"SET @@dolt_force_transaction_commit=1;",
+			"CREATE table t (pk int primary key, col1 varchar(100) default ('hello'));",
+			"alter table t add index idx1 (col1);",
+		},
+		RightSetUpScript: []string{
+			"alter table t add constraint CHECK (1 = 2)",
+		},
+		LeftSetUpScript: []string{
+			"insert into t values (1, DEFAULT);",
+		},
+		Assertions: []queries.ScriptTestAssertion{
+			{
+				Query:    "call dolt_merge('right');",
+				Expected: []sql.Row{{0, 0x1}},
+			},
+		},
+	},
 	{
 		Name: "check constraint violation - left side violates new check constraint",
 		AncSetUpScript: []string{
 			"set autocommit = 0;",
-			"CREATE table t (pk int primary key, col1 varchar(100));",
+			"CREATE table t (pk int primary key, col1 varchar(100) default ('hello'));",
 			"INSERT into t values (1, 'hi');",
 			"alter table t add index idx1 (col1);",
 		},
@@ -4393,7 +4455,7 @@ var ThreeWayMergeWithSchemaChangeTestScripts = []MergeScriptTest{
 			"alter table t add constraint CHECK (col1 != concat('he', 'llo'))",
 		},
 		LeftSetUpScript: []string{
-			"insert into t values (2, 'hello');",
+			"insert into t values (2, DEFAULT);",
 		},
 		Assertions: []queries.ScriptTestAssertion{
 			{