Fix issue with first week of month not being visible in calendar selector (#29722)

frontend/src/metabase/components/Calendar/Calendar.tsx

-/* eslint-disable react/prop-types */
 import React, { Component } from "react";
 import cx from "classnames";
 import moment, { Moment } from "moment-timezone";
@@ -13,7 +12,7 @@ import { CalendarDay } from "./Calendar.styled";
 
 export type SelectAll = "after" | "before";
 
-type Props = {
+export type CalendarProps = {
   initial?: Moment;
   selected?: Moment;
   selectedEnd?: Moment;
@@ -33,8 +32,8 @@ type State = {
   current?: Moment;
 };
 
-export default class Calendar extends Component<Props, State> {
-  constructor(props: Props) {
+export default class Calendar extends Component<CalendarProps, State> {
+  constructor(props: CalendarProps) {
     super(props);
     this.state = {
       current: moment(props.initial || undefined),
@@ -45,7 +44,7 @@ export default class Calendar extends Component<Props, State> {
     isRangePicker: true,
   };
 
-  UNSAFE_componentWillReceiveProps(nextProps: Props) {
+  UNSAFE_componentWillReceiveProps(nextProps: CalendarProps) {
     if (
       // `selected` became null or not null
       (nextProps.selected == null) !== (this.props.selected == null) ||
@@ -158,6 +157,11 @@ export default class Calendar extends Component<Props, State> {
     const firstDayOfWeek = getFirstDayOfWeekIndex();
     const date = moment(current).startOf("month").isoWeekday(firstDayOfWeek);
 
+    // if set week doesn't start with 1st day of month, then add the previous week
+    if (date.date() > 1) {
+      date.add(-1, "w");
+    }
+
     let done = false;
     let monthIndex = date.month();
     let count = 0;

frontend/src/metabase/components/Calendar/Calendar.unit.spec.js

-import React from "react";
-import moment from "moment-timezone";
-import mockDate from "mockdate";
-
-import { render, screen } from "@testing-library/react";
-import userEvent from "@testing-library/user-event";
-
-import Calendar from "metabase/components/Calendar";
-
-describe("Calendar", () => {
-  afterEach(() => {
-    mockDate.reset();
-  });
-
-  it("should switch months correctly", () => {
-    mockDate.set("2018-01-12T12:00:00Z", 0);
-    render(<Calendar selected={moment("2018-01-01")} onChange={() => {}} />);
-
-    const PREVIOUS = screen.getByRole("img", { name: /chevronleft icon/i });
-    const NEXT = screen.getByRole("img", { name: /chevronright icon/i });
-
-    expect(screen.getByText("January 2018")).toBeInTheDocument();
-
-    userEvent.click(PREVIOUS);
-    expect(screen.getByText("December 2017")).toBeInTheDocument();
-
-    userEvent.click(NEXT);
-    userEvent.click(NEXT);
-    expect(screen.getByText("February 2018")).toBeInTheDocument();
-  });
-});

frontend/src/metabase/components/Calendar.unit.spec.tsx → frontend/src/metabase/components/Calendar/Calendar.unit.spec.tsx

 import React from "react";
+import moment from "moment-timezone";
+import mockDate from "mockdate";
+import userEvent from "@testing-library/user-event";
 import { render, screen } from "__support__/ui";
+
 import MetabaseSettings from "metabase/lib/settings";
 import { updateMomentStartOfWeek } from "metabase/lib/i18n";
-import Calendar from "./Calendar";
+import Calendar, { CalendarProps } from "./Calendar";
 
 describe("Calendar", () => {
+  afterEach(() => {
+    mockDate.reset();
+  });
+
+  it("should switch months correctly", () => {
+    mockDate.set("2018-01-12T12:00:00Z", 0);
+    setup({ selected: moment("2018-01-01") });
+
+    const PREVIOUS = screen.getByRole("img", { name: /chevronleft icon/i });
+    const NEXT = screen.getByRole("img", { name: /chevronright icon/i });
+
+    expect(screen.getByText("January 2018")).toBeInTheDocument();
+
+    userEvent.click(PREVIOUS);
+    expect(screen.getByText("December 2017")).toBeInTheDocument();
+
+    userEvent.click(NEXT);
+    userEvent.click(NEXT);
+    expect(screen.getByText("February 2018")).toBeInTheDocument();
+  });
+
+  it("should render all days of current month by default", () => {
+    mockDate.set("2023-03-31T12:00:00Z", 0);
+    setup();
+
+    // check that listed dates are correct
+    expect(screen.getByTestId("calendar-weeks")).toHaveTextContent(
+      [
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
+        21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
+      ].join(""), // days in March 2023
+    );
+  });
+
   it("should render weekday short names", () => {
     setup();
 
@@ -51,6 +89,6 @@ describe("Calendar", () => {
   });
 });
 
-function setup() {
-  return render(<Calendar />);
+function setup(props?: Partial<CalendarProps>) {
+  return render(<Calendar {...props} />);
 }