Add blank-value filtering to column filters

Each filter dropdown (text/category/date) gains a 'show blanks only'
checkbox; when on, the column filters to rows where the field is empty
or whitespace-only (0/false are not blank), and the value control is
disabled. Implemented via a BLANK_SENTINEL key handled by matchesFilter,
with isBlank + 4 new unit tests. Not deployed.

Co-Authored-By: Claude <noreply@anthropic.com>

src/app/table-filter-ui.tsx

@@ -4,7 +4,12 @@ import { Button, Input, Checkbox, DatePicker, Space } from "antd";
 import dayjs from "dayjs";
 import type { ColumnType } from "antd/es/table";
 import type { FilterDropdownProps } from "antd/es/table/interface";
-import { inferFilterType, distinctValues, matchesFilter } from "./table-filters";
+import {
+  BLANK_SENTINEL,
+  inferFilterType,
+  distinctValues,
+  matchesFilter,
+} from "./table-filters";
 import type { DataRow, FilterType } from "./table-filters";
 
 const DATE_FMT = "YYYY-MM-DD";
@@ -30,93 +35,84 @@ export function FilterDropdown({
   type: FilterType;
   distinct: string[];
 }): React.ReactElement {
+  const blankOnly = selectedKeys.includes(BLANK_SENTINEL);
+
+  const footer = (
+    <Space style={{ marginTop: 8, display: "flex", justifyContent: "flex-end" }}>
+      <Button
+        size="small"
+        onClick={() => {
+          clearFilters?.();
+          confirm();
+        }}
+      >
+        重置
+      </Button>
+      <Button type="primary" size="small" onClick={() => confirm()}>
+        确定
+      </Button>
+    </Space>
+  );
+
+  let control: React.ReactNode;
   if (type === "date") {
     const [start, end] = decodeRange(selectedKeys);
-    return (
-      <div style={{ padding: 8 }}>
-        <DatePicker.RangePicker
-          value={[start, end]}
-          onChange={(dates) => {
-            if (!dates || dates[0] == null || dates[1] == null) {
-              setSelectedKeys([]);
-            } else {
-              const s = dates[0].format(DATE_FMT);
-              const e = dates[1].format(DATE_FMT);
-              setSelectedKeys([`${s}|${e}`]); // 单个编码键，供 onFilter 解码
-            }
-          }}
-        />
-        <Space style={{ marginTop: 8, display: "flex", justifyContent: "flex-end" }}>
-          <Button
-            size="small"
-            onClick={() => {
-              clearFilters?.();
-              confirm();
-            }}
-          >
-            重置
-          </Button>
-          <Button type="primary" size="small" onClick={() => confirm()}>
-            确定
-          </Button>
-        </Space>
-      </div>
+    control = (
+      <DatePicker.RangePicker
+        disabled={blankOnly}
+        value={[start, end]}
+        onChange={(dates) => {
+          if (!dates || dates[0] == null || dates[1] == null) {
+            setSelectedKeys([]);
+          } else {
+            const s = dates[0].format(DATE_FMT);
+            const e = dates[1].format(DATE_FMT);
+            setSelectedKeys([`${s}|${e}`]); // 单个编码键，供 onFilter 解码
+          }
+        }}
+        style={{ width: "100%" }}
+      />
     );
-  }
-
-  if (type === "category") {
-    return (
-      <div style={{ padding: 8, maxWidth: 260 }}>
-        <Checkbox.Group
-          style={{ display: "flex", flexDirection: "column", maxHeight: 240, overflow: "auto" }}
-          value={(selectedKeys as string[]) ?? []}
-          onChange={(vals) => setSelectedKeys(vals as React.Key[])}
-          options={distinct}
-        />
-        <Space style={{ marginTop: 8, display: "flex", justifyContent: "flex-end" }}>
-          <Button
-            size="small"
-            onClick={() => {
-              clearFilters?.();
-              confirm();
-            }}
-          >
-            重置
-          </Button>
-          <Button type="primary" size="small" onClick={() => confirm()}>
-            确定
-          </Button>
-        </Space>
-      </div>
+  } else if (type === "category") {
+    control = (
+      <Checkbox.Group
+        disabled={blankOnly}
+        style={{ display: "flex", flexDirection: "column", maxHeight: 240, overflow: "auto" }}
+        value={(selectedKeys as string[]) ?? []}
+        onChange={(vals) => setSelectedKeys(vals as React.Key[])}
+        options={distinct}
+      />
     );
-  }
-
-  // text
-  const textValue = selectedKeys[0] != null ? String(selectedKeys[0]) : "";
-  return (
-    <div style={{ padding: 8 }}>
+  } else {
+    // text
+    const textValue = blankOnly
+      ? ""
+      : selectedKeys[0] != null
+        ? String(selectedKeys[0])
+        : "";
+    control = (
       <Input
+        disabled={blankOnly}
         placeholder="输入关键字"
         value={textValue}
         onChange={(e) => setSelectedKeys(e.target.value ? [e.target.value] : [])}
         onPressEnter={() => confirm()}
-        style={{ marginBottom: 8, display: "block" }}
         allowClear
       />
-      <Space style={{ display: "flex", justifyContent: "flex-end" }}>
-        <Button
-          size="small"
-          onClick={() => {
-            clearFilters?.();
-            confirm();
-          }}
-        >
-          重置
-        </Button>
-        <Button type="primary" size="small" onClick={() => confirm()}>
-          确定
-        </Button>
-      </Space>
+    );
+  }
+
+  return (
+    <div style={{ padding: 8, maxWidth: type === "category" ? 260 : 320 }}>
+      <Checkbox
+        checked={blankOnly}
+        onChange={(e) => setSelectedKeys(e.target.checked ? [BLANK_SENTINEL] : [])}
+        style={{ marginBottom: 8 }}
+      >
+        仅显示空白
+      </Checkbox>
+      {control}
+      {footer}
     </div>
   );
 }

src/app/table-filters.test.ts

@@ -1,8 +1,10 @@
 import { describe, it, expect } from "vitest";
 import {
+  BLANK_SENTINEL,
   CATEGORY_THRESHOLD,
   distinctValues,
   inferFilterType,
+  isBlank,
   matchesFilter,
   nextLockedRow,
 } from "./table-filters";
@@ -79,3 +81,30 @@ describe("nextLockedRow", () => {
     expect(nextLockedRow("5", "7")).toBe("7");
   });
 });
+
+describe("isBlank", () => {
+  it("null/undefined/empty/whitespace are blank", () => {
+    expect(isBlank(null)).toBe(true);
+    expect(isBlank(undefined)).toBe(true);
+    expect(isBlank("")).toBe(true);
+    expect(isBlank("   ")).toBe(true);
+  });
+  it("non-empty values (including 0/false) are not blank", () => {
+    expect(isBlank("x")).toBe(false);
+    expect(isBlank(0)).toBe(false);
+    expect(isBlank(false)).toBe(false);
+  });
+});
+
+describe("matchesFilter blank sentinel", () => {
+  it("sentinel matches blank cells for any type", () => {
+    expect(matchesFilter("text", null, BLANK_SENTINEL)).toBe(true);
+    expect(matchesFilter("category", "", BLANK_SENTINEL)).toBe(true);
+    expect(matchesFilter("date", "   ", BLANK_SENTINEL)).toBe(true);
+  });
+  it("sentinel does not match non-blank cells", () => {
+    expect(matchesFilter("text", "hello", BLANK_SENTINEL)).toBe(false);
+    expect(matchesFilter("category", "A", BLANK_SENTINEL)).toBe(false);
+    expect(matchesFilter("date", "2024-01-01", BLANK_SENTINEL)).toBe(false);
+  });
+});

src/app/table-filters.ts

@@ -35,8 +35,18 @@ export function inferFilterType(
   return "text";
 }
 
+/** Sentinel filter key meaning "match blank/empty cells". */
+export const BLANK_SENTINEL = "__blank__";
+
+/** A cell is blank when it is null/undefined or trims to empty. 0/false are NOT blank. */
+export function isBlank(value: unknown): boolean {
+  if (value === null || value === undefined) return true;
+  return String(value).trim() === "";
+}
+
 /**
  * Does a cell match a single filter key?
+ * - BLANK_SENTINEL: cell is blank (any type)
  * - text: case-insensitive substring
  * - category: exact equality
  * - date: range encoded as "start|end" (either side may be ""), ISO string compare
@@ -46,6 +56,8 @@ export function matchesFilter(
   cellValue: unknown,
   filterValue: string
 ): boolean {
+  if (filterValue === BLANK_SENTINEL) return isBlank(cellValue);
+
   const cell =
     cellValue === null || cellValue === undefined ? "" : String(cellValue);