REP-6882 Track mismatch length

agg/accum/accumulators.go

@@ -0,0 +1,60 @@
+// Package accum exposes helper types for accumulation operators.
+package accum
+
+import "go.mongodb.org/mongo-driver/v2/bson"
+
+type Sum [1]any
+
+var _ bson.Marshaler = Sum{}
+
+func (s Sum) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{{"$sum", s[0]}})
+}
+
+//----------------------------------------------------------------------
+
+type Max [1]any
+
+var _ bson.Marshaler = Max{}
+
+func (m Max) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{{"$max", m[0]}})
+}
+
+//----------------------------------------------------------------------
+
+type FirstN struct {
+	N     any
+	Input any
+}
+
+var _ bson.Marshaler = FirstN{}
+
+func (t FirstN) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{
+		{"$firstN", bson.D{
+			{"n", t.N},
+			{"input", t.Input},
+		}},
+	})
+}
+
+//----------------------------------------------------------------------
+
+type TopN struct {
+	N      any
+	SortBy bson.D
+	Output any
+}
+
+var _ bson.Marshaler = TopN{}
+
+func (t TopN) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{
+		{"$topN", bson.D{
+			{"n", t.N},
+			{"sortBy", t.SortBy},
+			{"output", t.Output},
+		}},
+	})
+}

agg/agg.go

@@ -0,0 +1,235 @@
+// Package agg provides convenience types for aggregation operators.
+// This yields two major advantages over using bson.D or bson.M:
+// - simpler syntax
+// - auto-completion (i.e., via gopls)
+//
+// Guiding principles are:
+// - Prefer [1]any for unary operators (e.g., `$bsonSize`).
+// - Prefer struct types for operators with named parameters.
+// - Use functions sparingly, e.g., for “tuple” operators like `$in`.
+package agg
+
+import (
+	"go.mongodb.org/mongo-driver/v2/bson"
+)
+
+type Eq []any
+
+var _ bson.Marshaler = Eq{}
+
+func (e Eq) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{{"$eq", []any(e)}})
+}
+
+// ---------------------------------------------
+
+type Gt [2]any
+
+func (g Gt) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{{"$gt", []any(g[:])}})
+}
+
+// ---------------------------------------------
+
+func In[T any](needle any, haystack []T) bson.D {
+	return bson.D{{"$in", bson.A{needle, haystack}}}
+}
+
+// ---------------------------------------------
+
+type BSONSize [1]any
+
+var _ bson.Marshaler = BSONSize{}
+
+func (b BSONSize) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{{"$bsonSize", b[0]}})
+}
+
+// ---------------------------------------------
+
+type Type [1]any
+
+var _ bson.Marshaler = Type{}
+
+func (t Type) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{{"$type", t[0]}})
+}
+
+// ---------------------------------------------
+
+type Not [1]any
+
+var _ bson.Marshaler = Not{}
+
+func (n Not) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{{"$not", n[0]}})
+}
+
+// ---------------------------------------------
+
+type And []any
+
+var _ bson.Marshaler = And{}
+
+func (a And) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{
+		{"$and", []any(a)},
+	})
+}
+
+// ---------------------------------------------
+
+type Or []any
+
+var _ bson.Marshaler = Or{}
+
+func (o Or) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{
+		{"$or", []any(o)},
+	})
+}
+
+// ---------------------------------------------
+
+type MergeObjects []any
+
+var _ bson.Marshaler = MergeObjects{}
+
+func (m MergeObjects) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{
+		{"$mergeObjects", []any(m)},
+	})
+}
+
+// ---------------------------------------------
+
+type GetField struct {
+	Input, Field any
+}
+
+var _ bson.Marshaler = GetField{}
+
+func (gf GetField) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(
+		bson.D{
+			{"$getField", bson.D{
+				{"input", gf.Input},
+				{"field", gf.Field},
+			}},
+		},
+	)
+}
+
+// ---------------------------------------------
+
+type Cond struct {
+	If, Then, Else any
+}
+
+var _ bson.Marshaler = Cond{}
+
+func (c Cond) D() bson.D {
+	return bson.D{
+		{"$cond", bson.D{
+			{"if", c.If},
+			{"then", c.Then},
+			{"else", c.Else},
+		}},
+	}
+}
+
+func (c Cond) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(c.D())
+}
+
+// ---------------------------------------------
+
+type Switch struct {
+	Branches []SwitchCase
+	Default  any
+}
+
+var _ bson.Marshaler = Switch{}
+
+type SwitchCase struct {
+	Case any
+	Then any
+}
+
+func (s Switch) D() bson.D {
+	return bson.D{{"$switch", bson.D{
+		{"branches", s.Branches},
+		{"default", s.Default},
+	}}}
+}
+
+func (s Switch) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(s.D())
+}
+
+// ---------------------------------------------
+
+type ArrayElemAt struct {
+	Array any
+	Index int
+}
+
+var _ bson.Marshaler = ArrayElemAt{}
+
+func (a ArrayElemAt) D() bson.D {
+	return bson.D{{"$arrayElemAt", bson.A{
+		a.Array,
+		a.Index,
+	}}}
+}
+
+func (a ArrayElemAt) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(a.D())
+}
+
+// ---------------------------------------------
+
+type Map struct {
+	Input, As, In any
+}
+
+var _ bson.Marshaler = Map{}
+
+func (m Map) D() bson.D {
+	return bson.D{
+		{"$map", bson.D{
+			{"input", m.Input},
+			{"as", m.As},
+			{"in", m.In},
+		}},
+	}
+}
+
+func (m Map) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(m.D())
+}
+
+// ------------------------------------------
+
+type Filter struct {
+	Input, As, Cond, Limit any
+}
+
+var _ bson.Marshaler = Filter{}
+
+func (f Filter) D() bson.D {
+	d := bson.D{
+		{"input", f.Input},
+		{"as", f.As},
+		{"cond", f.Cond},
+	}
+
+	if f.Limit != nil {
+		d = append(d, bson.E{"limit", f.Limit})
+	}
+	return bson.D{{"$filter", d}}
+}
+
+func (f Filter) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(f.D())
+}

agg/helpers/exist.go

@@ -0,0 +1,14 @@
+// Package helpers exposes functions that express common operations
+// that don’t map to a single aggregation operator.
+package helpers
+
+import (
+	"github.com/10gen/migration-verifier/agg"
+	"go.mongodb.org/mongo-driver/v2/bson"
+)
+
+type Exists [1]any
+
+func (e Exists) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(agg.Not{agg.Eq{"missing", agg.Type{e[0]}}})
+}

agg/math.go

@@ -0,0 +1,11 @@
+package agg
+
+import "go.mongodb.org/mongo-driver/v2/bson"
+
+type Subtract [2]any
+
+var _ bson.Marshaler = Subtract{}
+
+func (s Subtract) MarshalBSON() ([]byte, error) {
+	return bson.Marshal(bson.D{{"$subtract", [2]any(s)}})
+}