Type inference can have access to the environment. (#15982)

In this case, to fetch the field type.

frontend/src/metabase-lib/lib/Dimension.js

@@ -1010,21 +1010,32 @@ export class ExpressionDimension extends Dimension {
     if (query) {
       const datasetQuery = query.query();
       const expressions = datasetQuery ? datasetQuery.expressions : {};
-      type = infer(expressions[this.name()]);
+      const env = mbql => {
+        const dimension = Dimension.parseMBQL(
+          mbql,
+          this._metadata,
+          this._query,
+        );
+        return dimension.field().base_type;
+      };
+      type = infer(expressions[this.name()], env);
     } else {
       type = infer(this._args[0]);
     }
 
-    let base_type = "type/Float"; // fallback
-    switch (type) {
-      case MONOTYPE.String:
-        base_type = "type/Text";
-        break;
-      case MONOTYPE.Boolean:
-        base_type = "type/Boolean";
-        break;
-      default:
-        break;
+    let base_type = type;
+    if (!type.startsWith("type/")) {
+      base_type = "type/Float"; // fallback
+      switch (type) {
+        case MONOTYPE.String:
+          base_type = "type/Text";
+          break;
+        case MONOTYPE.Boolean:
+          base_type = "type/Boolean";
+          break;
+        default:
+          break;
+      }
     }
 
     return new Field({

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

@@ -8,7 +8,7 @@ export const MONOTYPE = {
   Boolean: "boolean",
 };
 
-export function infer(mbql) {
+export function infer(mbql, env) {
   if (!Array.isArray(mbql)) {
     return typeof mbql;
   }
@@ -50,5 +50,9 @@ export function infer(mbql) {
     }
   }
 
+  if (op === "field" && env) {
+    return env(mbql);
+  }
+
   return MONOTYPE.Undefined;
 }

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

@@ -3,7 +3,7 @@ import { infer } from "metabase/lib/expressions/typeinferencer";
 
 describe("metabase/lib/expressions/typeinferencer", () => {
   function resolve(kind, name) {
-    return [kind, name];
+    return ["field", name];
   }
   function compileAs(source, startRule) {
     let mbql = null;
@@ -22,8 +22,21 @@ describe("metabase/lib/expressions/typeinferencer", () => {
     return mbql;
   }
 
+  function mockEnv(fieldRef) {
+    switch (fieldRef[1]) {
+      case "Price":
+        return "number";
+      case "FirstName":
+        return "string";
+      case "BirthDate":
+        return "type/Temporal";
+      case "Location":
+        return "type/Coordinate";
+    }
+  }
+
   function type(expression) {
-    return infer(tryCompile(expression));
+    return infer(tryCompile(expression), mockEnv);
   }
 
   it("should infer the type of primitives", () => {
@@ -72,6 +85,13 @@ describe("metabase/lib/expressions/typeinferencer", () => {
     expect(type("Length([Category]) > 0")).toEqual("boolean");
   });
 
+  it("should relay the field type", () => {
+    expect(type("[Price]")).toEqual("number");
+    expect(type("([FirstName])")).toEqual("string");
+    expect(type("[BirthDate]")).toEqual("type/Temporal");
+    expect(type("[Location]")).toEqual("type/Coordinate");
+  });
+
   it.skip("should infer the result of CASE", () => {
     expect(type("CASE([X], 1, 2)")).toEqual("number");
     expect(type("CASE([Y], 'this', 'that')")).toEqual("string");

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

@@ -5,6 +5,7 @@ import {
   _typeUsingPlaceholder,
   openOrdersTable,
   openProductsTable,
+  openPeopleTable,
   visitQuestionAdhoc,
 } from "__support__/e2e/cypress";
 
@@ -435,6 +436,23 @@ describe("scenarios > question > custom columns", () => {
       cy.findByPlaceholderText("Enter a number").should("not.exist");
       cy.findByPlaceholderText("Enter some text");
     });
+
+    it("should relay the type of a date field", () => {
+      openPeopleTable({ mode: "notebook" });
+      cy.findByText("Custom column").click();
+      popover().within(() => {
+        _typeUsingGet("[contenteditable='true']", "[Birth Date]", 400);
+        _typeUsingPlaceholder("Something nice and descriptive", "DoB");
+        cy.findByText("Done").click();
+      });
+      cy.findByText("Filter").click();
+      popover()
+        .findByText("DoB")
+        .click();
+      cy.findByPlaceholderText("Enter a number").should("not.exist");
+      cy.findByText("Previous");
+      cy.findByText("Days");
+    });
   });
 
   it("should handle using `case()` when referencing the same column names (metabase#14854)", () => {