From ff10e0e85e561c98e5936822c0d5d8af563a32a0 Mon Sep 17 00:00:00 2001
From: raeidish <118611562+raeidish@users.noreply.github.com>
Date: Tue, 2 May 2023 15:37:49 +0200
Subject: [PATCH 1/3] Remove version and name assertions in integration tests
 (#2552)

Closes #2500.
---
 integration/commands_diagnostic_test.go | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/integration/commands_diagnostic_test.go b/integration/commands_diagnostic_test.go
index ba4b3964a764..ecaea501a875 100644
--- a/integration/commands_diagnostic_test.go
+++ b/integration/commands_diagnostic_test.go
@@ -16,7 +16,6 @@ package integration
 
 import (
 	"net"
-	"runtime"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -222,11 +221,6 @@ func TestCommandsDiagnosticHostInfo(t *testing.T) {
 	os := m["os"].(bson.D)
 	assert.Equal(t, []string{"type", "name", "version"}, CollectKeys(t, os))
 
-	if runtime.GOOS == "linux" {
-		require.NotEmpty(t, os.Map()["name"], "os name should not be empty")
-		require.NotEmpty(t, os.Map()["version"], "os version should not be empty")
-	}
-
 	system := m["system"].(bson.D)
 	keys := CollectKeys(t, system)
 	assert.Contains(t, keys, "currentTime")

From 30dd84203a10aa5ed21b7245043534cb8ae365cf Mon Sep 17 00:00:00 2001
From: Alexey Palazhchenko <alexey.palazhchenko@ferretdb.io>
Date: Wed, 3 May 2023 14:47:35 +0400
Subject: [PATCH 2/3] Add helpers for iterators and generators (#2542)

---
 internal/util/iterator/count.go         | 42 +++++++++++++
 internal/util/iterator/func.go          | 79 +++++++++++++++++++++++++
 internal/util/iterator/iterator.go      |  2 +-
 internal/util/iterator/iterator_test.go | 36 +++++++++++
 internal/util/iterator/slice.go         |  8 ++-
 internal/util/iterator/values.go        |  1 +
 internal/util/iterator/with_close.go    | 15 ++---
 7 files changed, 172 insertions(+), 11 deletions(-)
 create mode 100644 internal/util/iterator/count.go
 create mode 100644 internal/util/iterator/func.go

diff --git a/internal/util/iterator/count.go b/internal/util/iterator/count.go
new file mode 100644
index 000000000000..ecb67e4f0d2f
--- /dev/null
+++ b/internal/util/iterator/count.go
@@ -0,0 +1,42 @@
+// Copyright 2021 FerretDB Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package iterator
+
+import "errors"
+
+// ConsumeCount returns the number of elements in the iterator.
+// ErrIteratorDone error is returned as nil; any other error is returned as-is.
+//
+// Iterator is always closed at the end.
+func ConsumeCount[K, V any](iter Interface[K, V]) (int, error) {
+	defer iter.Close()
+
+	var count int
+	var err error
+
+	for {
+		_, _, err = iter.Next()
+		if err == nil {
+			count++
+			continue
+		}
+
+		if errors.Is(err, ErrIteratorDone) {
+			err = nil
+		}
+
+		return count, err
+	}
+}
diff --git a/internal/util/iterator/func.go b/internal/util/iterator/func.go
new file mode 100644
index 000000000000..42db78acbd25
--- /dev/null
+++ b/internal/util/iterator/func.go
@@ -0,0 +1,79 @@
+// Copyright 2021 FerretDB Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package iterator
+
+import (
+	"fmt"
+	"sync"
+
+	"github.com/FerretDB/FerretDB/internal/util/resource"
+)
+
+// NextFunc is a part of Interface for the Next method.
+type NextFunc[K, V any] func() (K, V, error)
+
+// valuesIterator implements iterator.Interface.
+//
+//nolint:vet // for readability
+type funcIterator[K, V any] struct {
+	m sync.Mutex
+	f NextFunc[K, V]
+
+	token *resource.Token
+}
+
+// ForFunc returns an iterator for the given function.
+func ForFunc[K, V any](f NextFunc[K, V]) Interface[K, V] {
+	iter := &funcIterator[K, V]{
+		f:     f,
+		token: resource.NewToken(),
+	}
+
+	resource.Track(iter, iter.token)
+
+	return iter
+}
+
+// Next implements iterator.Interface.
+func (iter *funcIterator[K, V]) Next() (K, V, error) {
+	iter.m.Lock()
+	defer iter.m.Unlock()
+
+	if iter.f == nil {
+		var k K
+		var v V
+
+		return k, v, fmt.Errorf("%w (f is nil)", ErrIteratorDone)
+	}
+
+	return iter.f()
+}
+
+// Close implements iterator.Interface.
+func (iter *funcIterator[K, V]) Close() {
+	iter.m.Lock()
+	defer iter.m.Unlock()
+
+	iter.f = nil
+
+	resource.Untrack(iter, iter.token)
+}
+
+// check interfaces
+var (
+	_ Interface[any, any] = (*funcIterator[any, any])(nil)
+	_ NextFunc[any, any]  = (*funcIterator[any, any])(nil).Next
+	_ Closer              = (*funcIterator[any, any])(nil)
+)
diff --git a/internal/util/iterator/iterator.go b/internal/util/iterator/iterator.go
index 805e5f03e0b8..e10883f6fe64 100644
--- a/internal/util/iterator/iterator.go
+++ b/internal/util/iterator/iterator.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package iterator describes a generic Iterator interface.
+// Package iterator describes a generic Iterator interface and related utilities.
 package iterator
 
 import "errors"
diff --git a/internal/util/iterator/iterator_test.go b/internal/util/iterator/iterator_test.go
index 13fce12f878f..76d2c5af4542 100644
--- a/internal/util/iterator/iterator_test.go
+++ b/internal/util/iterator/iterator_test.go
@@ -54,3 +54,39 @@ func TestConsumeValuesN(t *testing.T) {
 	require.NoError(t, err)
 	assert.Nil(t, actual)
 }
+
+func TestForFunc(t *testing.T) {
+	var i int
+	f := func() (struct{}, int, error) {
+		var k struct{}
+
+		i++
+		if i > 3 {
+			return k, 0, ErrIteratorDone
+		}
+
+		return k, i, nil
+	}
+
+	iter1 := ForFunc(f)
+	iter2 := ForFunc(f)
+
+	defer iter1.Close()
+	defer iter2.Close()
+
+	_, v, err := iter1.Next()
+	require.NoError(t, err)
+	assert.Equal(t, 1, v)
+
+	_, v, err = iter2.Next()
+	require.NoError(t, err)
+	assert.Equal(t, 2, v)
+
+	_, v, err = iter1.Next()
+	require.NoError(t, err)
+	assert.Equal(t, 3, v)
+
+	_, v, err = iter2.Next()
+	require.ErrorIs(t, err, ErrIteratorDone)
+	assert.Equal(t, 0, v)
+}
diff --git a/internal/util/iterator/slice.go b/internal/util/iterator/slice.go
index 0f6269ddd0ac..9ca84d886d41 100644
--- a/internal/util/iterator/slice.go
+++ b/internal/util/iterator/slice.go
@@ -15,6 +15,7 @@
 package iterator
 
 import (
+	"fmt"
 	"sync"
 
 	"github.com/FerretDB/FerretDB/internal/util/resource"
@@ -50,9 +51,9 @@ func (iter *sliceIterator[V]) Next() (int, V, error) {
 	iter.n++
 	n := int(iter.n) - 1
 
-	var zero V
-	if n >= len(iter.s) {
-		return 0, zero, ErrIteratorDone
+	if l := len(iter.s); n >= l {
+		var v V
+		return 0, v, fmt.Errorf("%w (n (%d) >= len (%d)", ErrIteratorDone, n, l)
 	}
 
 	return n, iter.s[n], nil
@@ -71,5 +72,6 @@ func (iter *sliceIterator[V]) Close() {
 // check interfaces
 var (
 	_ Interface[int, any] = (*sliceIterator[any])(nil)
+	_ NextFunc[int, any]  = (*sliceIterator[any])(nil).Next
 	_ Closer              = (*sliceIterator[any])(nil)
 )
diff --git a/internal/util/iterator/values.go b/internal/util/iterator/values.go
index a9584059f8ed..51d86215562b 100644
--- a/internal/util/iterator/values.go
+++ b/internal/util/iterator/values.go
@@ -105,5 +105,6 @@ func (iter *valuesIterator[K, V]) Close() {
 // check interfaces
 var (
 	_ Interface[struct{}, any] = (*valuesIterator[any, any])(nil)
+	_ NextFunc[struct{}, any]  = (*valuesIterator[any, any])(nil).Next
 	_ Closer                   = (*valuesIterator[any, any])(nil)
 )
diff --git a/internal/util/iterator/with_close.go b/internal/util/iterator/with_close.go
index 51125cf3321f..812393cf151d 100644
--- a/internal/util/iterator/with_close.go
+++ b/internal/util/iterator/with_close.go
@@ -14,8 +14,8 @@
 
 package iterator
 
-// withClose wraps an iterator with a custom close function.
-type withClose[K, V any] struct {
+// withCloseIterator wraps an iterator with a custom close function.
+type withCloseIterator[K, V any] struct {
 	iter  Interface[K, V]
 	close func()
 }
@@ -24,25 +24,26 @@ type withClose[K, V any] struct {
 //
 // That function should call Close() method of the wrapped iterator.
 func WithClose[K, V any](iter Interface[K, V], close func()) Interface[K, V] {
-	return &withClose[K, V]{
+	return &withCloseIterator[K, V]{
 		iter:  iter,
 		close: close,
 	}
 }
 
 // Next implements iterator.Interface by calling Next() method of the wrapped iterator.
-func (iter *withClose[K, V]) Next() (K, V, error) {
+func (iter *withCloseIterator[K, V]) Next() (K, V, error) {
 	return iter.iter.Next()
 }
 
 // Close implements iterator.Interface by calling the provided close function.
-func (iter *withClose[K, V]) Close() {
+func (iter *withCloseIterator[K, V]) Close() {
 	// we might want to wrap it with sync.Once if needed
 	iter.close()
 }
 
 // check interfaces
 var (
-	_ Interface[any, any] = (*withClose[any, any])(nil)
-	_ Closer              = (*withClose[any, any])(nil)
+	_ Interface[any, any] = (*withCloseIterator[any, any])(nil)
+	_ NextFunc[any, any]  = (*withCloseIterator[any, any])(nil).Next
+	_ Closer              = (*withCloseIterator[any, any])(nil)
 )

From 717f0fa34d006074cabec360712c929d63a8fe60 Mon Sep 17 00:00:00 2001
From: Alexey Palazhchenko <alexey.palazhchenko@ferretdb.io>
Date: Wed, 3 May 2023 15:16:02 +0400
Subject: [PATCH 3/3] Do various small cleanups (#2561)

---
 integration/Taskfile.yml           |  2 +-
 internal/handlers/common/params.go | 37 ++++++++++++++++++++++--------
 internal/types/document.go         |  9 ++++++++
 internal/util/iterator/count.go    |  2 +-
 internal/util/iterator/values.go   |  2 +-
 internal/util/must/must.go         | 13 +++++++++++
 tools/Taskfile.yml                 |  2 +-
 7 files changed, 53 insertions(+), 14 deletions(-)

diff --git a/integration/Taskfile.yml b/integration/Taskfile.yml
index f104d12f3373..58e806d9f014 100644
--- a/integration/Taskfile.yml
+++ b/integration/Taskfile.yml
@@ -5,7 +5,7 @@ version: 3
 vars:
   BENCHTIME: 5s
   BENCHNAME: '{{default "." .BENCHNAME}}'
-  RACEFLAG: -race={{ne OS "windows"}}
+  RACEFLAG: -race={{and (ne OS "windows") (ne ARCH "arm") (ne ARCH "riscv64")}}
 
 tasks:
   env-data:
diff --git a/internal/handlers/common/params.go b/internal/handlers/common/params.go
index 53f7095c321b..1d95ecb7c829 100644
--- a/internal/handlers/common/params.go
+++ b/internal/handlers/common/params.go
@@ -25,12 +25,13 @@ import (
 	"github.com/FerretDB/FerretDB/internal/util/must"
 )
 
-// GetRequiredParam returns doc's value for key or protocol error for missing or invalid parameter.
+// GetRequiredParam returns doc's value for key
+// or protocol error for missing key or invalid type.
 func GetRequiredParam[T types.Type](doc *types.Document, key string) (T, error) {
 	var zero T
 
-	v, err := doc.Get(key)
-	if err != nil {
+	v, _ := doc.Get(key)
+	if v == nil {
 		msg := fmt.Sprintf("required parameter %q is missing", key)
 		return zero, commonerrors.NewCommandErrorMsgWithArgument(commonerrors.ErrBadValue, msg, key)
 	}
@@ -44,13 +45,15 @@ func GetRequiredParam[T types.Type](doc *types.Document, key string) (T, error)
 	return res, nil
 }
 
-// GetOptionalParam returns doc's value for key, default value for missing parameter, or protocol error for invalid parameter.
+// GetOptionalParam returns doc's value for key, default value for missing parameter,
+// or protocol error for invalid type.
 func GetOptionalParam[T types.Type](doc *types.Document, key string, defaultValue T) (T, error) {
-	v, err := doc.Get(key)
-	if err != nil {
+	v, _ := doc.Get(key)
+	if v == nil {
 		return defaultValue, nil
 	}
 
+	// require exact type; do not threat nulls as default values in this helper
 	res, ok := v.(T)
 	if !ok {
 		msg := fmt.Sprintf(
@@ -64,13 +67,27 @@ func GetOptionalParam[T types.Type](doc *types.Document, key string, defaultValu
 	return res, nil
 }
 
+// GetOptionalNullParam returns doc's value for key, default value for missing parameter or null,
+// or protocol error for other invalid type.
+func GetOptionalNullParam[T types.Type](doc *types.Document, key string, defaultValue T) (T, error) {
+	v, err := GetOptionalParam(doc, key, defaultValue)
+	if err != nil {
+		// the only possible error here is type mismatch, so the key is present
+		if _, ok := must.NotFail(doc.Get(key)).(types.NullType); ok {
+			err = nil
+		}
+	}
+
+	return v, err
+}
+
 // GetBoolOptionalParam returns doc's bool value for key.
 // Non-zero double, long, and int values return true.
 // Zero values for those types, as well as nulls and missing fields, return false.
 // Other types return a protocol error.
 func GetBoolOptionalParam(doc *types.Document, key string) (bool, error) {
-	v, err := doc.Get(key)
-	if err != nil {
+	v, _ := doc.Get(key)
+	if v == nil {
 		return false, nil
 	}
 
@@ -495,8 +512,8 @@ func multiplyLongSafely(v1, v2 int64) (int64, error) {
 
 // GetOptionalPositiveNumber returns doc's value for key or protocol error for invalid parameter.
 func GetOptionalPositiveNumber(document *types.Document, key string) (int32, error) {
-	v, err := document.Get(key)
-	if err != nil {
+	v, _ := document.Get(key)
+	if v == nil {
 		return 0, nil
 	}
 
diff --git a/internal/types/document.go b/internal/types/document.go
index ce6761fd62dc..2bc60b1526b6 100644
--- a/internal/types/document.go
+++ b/internal/types/document.go
@@ -236,6 +236,15 @@ func (d *Document) Has(key string) bool {
 
 // Get returns a value at the given key.
 // If the key is duplicated, it panics.
+//
+// The only possible error is returned for a missing key.
+// In that case, Get returns nil for the value.
+// The new code is encouraged to do this:
+//
+//	v, _ := d.Get("key")
+//	if v == nil { ... }
+//
+// The error value will be removed in the future.
 func (d *Document) Get(key string) (any, error) {
 	if d.isKeyDuplicate(key) {
 		panic(fmt.Sprintf("types.Document.Get: key is duplicated: %s", key))
diff --git a/internal/util/iterator/count.go b/internal/util/iterator/count.go
index ecb67e4f0d2f..7bfa688ab368 100644
--- a/internal/util/iterator/count.go
+++ b/internal/util/iterator/count.go
@@ -19,7 +19,7 @@ import "errors"
 // ConsumeCount returns the number of elements in the iterator.
 // ErrIteratorDone error is returned as nil; any other error is returned as-is.
 //
-// Iterator is always closed at the end.
+// It always closes the iterator.
 func ConsumeCount[K, V any](iter Interface[K, V]) (int, error) {
 	defer iter.Close()
 
diff --git a/internal/util/iterator/values.go b/internal/util/iterator/values.go
index 51d86215562b..d00590f3ed3c 100644
--- a/internal/util/iterator/values.go
+++ b/internal/util/iterator/values.go
@@ -23,7 +23,7 @@ import (
 // ConsumeValues consumes all values from iterator until it is done.
 // ErrIteratorDone error is returned as nil; any other error is returned as-is.
 //
-// Iterator is always closed at the end.
+// It always closes the iterator.
 func ConsumeValues[K, V any](iter Interface[K, V]) ([]V, error) {
 	defer iter.Close()
 
diff --git a/internal/util/must/must.go b/internal/util/must/must.go
index e29aee547f09..3eccb8dc4252 100644
--- a/internal/util/must/must.go
+++ b/internal/util/must/must.go
@@ -15,6 +15,8 @@
 // Package must provides helper functions that panic on error.
 package must
 
+import "fmt"
+
 // NotFail panics if the error is not nil, returns res otherwise.
 //
 // Use that function only for static initialization, test code, or code that "can't" fail.
@@ -36,6 +38,17 @@ func NoError(err error) {
 	}
 }
 
+// NotBeZero panics if argument has zero value.
+//
+// Use that function only for static initialization, test code, or code that "can't" fail.
+// When in doubt, don't.
+func NotBeZero[T comparable](v T) {
+	var zero T
+	if v == zero {
+		panic(fmt.Sprintf("v has zero value (%#v)", v))
+	}
+}
+
 // BeTrue panic if the b is not true.
 //
 // Use that function only for static initialization, test code, or statemants that
diff --git a/tools/Taskfile.yml b/tools/Taskfile.yml
index c474eeaf6421..3c37afe51c1a 100644
--- a/tools/Taskfile.yml
+++ b/tools/Taskfile.yml
@@ -3,7 +3,7 @@
 version: 3
 
 vars:
-  RACEFLAG: -race={{ne OS "windows"}}
+  RACEFLAG: -race={{and (ne OS "windows") (ne ARCH "arm") (ne ARCH "riscv64")}}
 
 tasks:
   tools-test: