Custom expression: new function ISNULL() and ISEMPTY() (#14866)

These new functions are to support MBQL's is-null and is-empty.

docs/users-guide/expressions.md

@@ -68,6 +68,8 @@ This would return rows where `Created At` is between January 1, 2020 and March 3
 | Exp                | `exp(column)`                            | Returns Euler's number, e, raised to the power of the supplied number.                                                                                             | `exp([Interest Months])`                                           |
 | Floor              | `floor(column)`                          | Rounds a decimal number down.                                                                                                                                      | `floor([Price])`                                                   |
 | Interval           | `interval(column, number, text)`         | Checks a date column's values to see if they're within the relative range.                                                                                         | `interval([Created At], -1, "month")`                              |
+| IsEmpty            | `isempty(column)`                        | Returns true if the column is empty.                                                                                                                               | `isempty([Discount])`                                              |
+| IsNull             | `isnull(column)`                         | Returns true if the column is null.                                                                                                                                | `isnull([Tax])`                                                    |
 | Left trim          | `ltrim(text)`                            | Removes leading whitespace from a string of text.                                                                                                                  | `ltrim([Comment])`                                                 |
 | Length             | `length(text)`                           | Returns the number of characters in text.                                                                                                                          | `length([Comment])`                                                |
 | Log                | `log(column)`                            | Returns the base 10 log of the number.                                                                                                                             | `log([Value])`                                                     |

frontend/src/metabase/lib/expressions/config.js

@@ -224,6 +224,16 @@ export const MBQL_CLAUSES = {
     type: "boolean",
     args: ["expression", "number", "string"],
   },
+  "is-null": {
+    displayName: `isnull`,
+    type: "boolean",
+    args: ["expression"],
+  },
+  "is-empty": {
+    displayName: `isempty`,
+    type: "boolean",
+    args: ["expression"],
+  },
   // other expression functions
   coalesce: {
     displayName: `coalesce`,
@@ -380,6 +390,8 @@ export const EXPRESSION_FUNCTIONS = new Set([
   "starts-with",
   "between",
   "time-interval",
+  "is-null",
+  "is-empty",
   // other
   "coalesce",
 ]);

frontend/src/metabase/lib/expressions/helper_text_strings.js

@@ -461,6 +461,30 @@ const helperTextStrings = [
       },
     ],
   },
+  {
+    name: "is-null",
+    structure: "isnull(" + t`column` + ")",
+    description: t`Checks if a column is null`,
+    example: "isnull([" + t`Discount` + '")',
+    args: [
+      {
+        name: t`column`,
+        description: t`The column to check.`,
+      },
+    ],
+  },
+  {
+    name: "is-empty",
+    structure: "isempty(" + t`column` + ")",
+    description: t`Checks if a column is empty`,
+    example: "isempty([" + t`Name` + '")',
+    args: [
+      {
+        name: t`column`,
+        description: t`The column to check.`,
+      },
+    ],
+  },
   {
     name: "coalesce",
     structure: "coalesce(" + t`value1` + ", " + t`value2` + ", …)",

frontend/test/metabase/lib/expressions/suggest.unit.spec.js

@@ -64,6 +64,8 @@ const FILTER_FUNCTIONS = [
   { text: "contains(", type: "functions" },
   { text: "endsWith(", type: "functions" },
   { text: "interval(", type: "functions" },
+  { text: "isempty(", type: "functions" },
+  { text: "isnull(", type: "functions" },
   { text: "startsWith(", type: "functions" },
 ];
 const EXPRESSION_OPERATORS = [

frontend/test/metabase/lib/expressions/typechecker.unit.spec.js

@@ -113,6 +113,8 @@ describe("type-checker", () => {
       expect(filter("5 <= Q").segments).toEqual([]);
       expect(filter("Between([BIG],3,7)").segments).toEqual([]);
       expect(filter("Contains([GI],'Joe')").segments).toEqual([]);
+      expect(filter("IsEmpty([Discount])").segments).toEqual([]);
+      expect(filter("IsNull([Tax])").segments).toEqual([]);
     });
 
     it("should resolve dimensions correctly", () => {
@@ -124,6 +126,8 @@ describe("type-checker", () => {
       expect(filter("5 <= Q").dimensions).toEqual(["Q"]);
       expect(filter("Between([BIG],3,7)").dimensions).toEqual(["BIG"]);
       expect(filter("Contains([GI],'Joe')").dimensions).toEqual(["GI"]);
+      expect(filter("IsEmpty([Discount])").dimensions).toEqual(["Discount"]);
+      expect(filter("IsNull([Tax])").dimensions).toEqual(["Tax"]);
     });
 
     it("should resolve dimensions and segments correctly", () => {

frontend/test/metabase/scenarios/question/filter.cy.spec.js

@@ -3,6 +3,7 @@ import {
   restore,
   openOrdersTable,
   openProductsTable,
+  openReviewsTable,
   popover,
   visitQuestionAdhoc,
 } from "__support__/cypress";
@@ -779,4 +780,83 @@ describe("scenarios > question > filter", () => {
     cy.wait("@cardQuery");
     cy.findByText("Rye").should("not.exist");
   });
+
+  it("should filter using IsNull() and IsEmpty()", () => {
+    openReviewsTable({ mode: "notebook" });
+    cy.findByText("Filter").click();
+    cy.findByText("Custom Expression").click();
+
+    cy.get("[contenteditable='true']")
+      .click()
+      .clear()
+      .type("NOT IsNull([Rating])", { delay: 50 });
+    cy.findAllByRole("button")
+      .contains("Done")
+      .should("not.be.disabled")
+      .click();
+
+    cy.get(".QueryBuilder .Icon-add").click();
+
+    cy.findByText("Custom Expression").click();
+    cy.get("[contenteditable='true']")
+      .click()
+      .clear()
+      .type("NOT IsEmpty([Reviewer])", { delay: 50 });
+    cy.findAllByRole("button")
+      .contains("Done")
+      .should("not.be.disabled")
+      .click();
+
+    // check that filter is applied and rows displayed
+    cy.findByText("Visualize").click();
+    cy.contains("Showing 1,112 rows");
+  });
+
+  it("should convert 'is empty' on a text column to a custom expression using IsEmpty()", () => {
+    openReviewsTable();
+    cy.contains("Reviewer").click();
+    cy.findByText("Filter by this column").click();
+    cy.findByText("Is").click();
+    cy.findByText("Is empty").click();
+    cy.findByText("Update filter").click();
+
+    // filter out everything
+    cy.contains("Showing 0 rows");
+
+    // change the corresponding custom expression
+    cy.findByText("Reviewer is empty").click();
+    cy.get(".Icon-chevronleft").click();
+    cy.findByText("Custom Expression").click();
+    cy.get("[contenteditable='true']").contains("isempty([Reviewer])");
+    cy.get("[contenteditable='true']")
+      .click()
+      .clear()
+      .type("NOT IsEmpty([Reviewer])", { delay: 50 });
+    cy.findByText("Done").click();
+    cy.contains("Showing 1,112 rows");
+  });
+
+  it("should convert 'is empty' on a numeric column to a custom expression using IsNull()", () => {
+    openReviewsTable();
+    cy.contains("Rating").click();
+    cy.findByText("Filter by this column").click();
+    cy.findByText("Equal to").click();
+    cy.findByText("Is empty").click();
+    cy.findByText("Update filter").click();
+
+    // filter out everything
+    cy.contains("Showing 0 rows");
+
+    // change the corresponding custom expression
+    cy.findByText("Rating is empty").click();
+    cy.get(".Icon-chevronleft").click();
+    cy.findByText("Custom Expression").click();
+    cy.get("[contenteditable='true']").contains("isnull([Rating])");
+    cy.get("[contenteditable='true']")
+      .click()
+      .clear()
+      .type("NOT IsNull([Rating])", { delay: 50 });
+    cy.findByText("Done").click();
+    cy.contains("Showing 1,112 rows");
+  });
 });