Align match behavior with case/==

Makes `["match", ["get", k], label, match, otherwise]` equivalent to `["case", ["==", ["get", k], label], match, otherwise]`. This changes the behavior of match expressions where the runtime type of the input does not match the type of the labels: previously such expressions produced a runtime type error and then fell back to the property default value; now they produce the fallback value from the match expression.

src/style-spec/expression/definitions/match.js

@@ -3,11 +3,11 @@
 import assert from 'assert';
 
 import { typeOf } from '../values';
+import { ValueType, type Type } from '../types';
 
 import type { Expression } from '../expression';
 import type ParsingContext from '../parsing_context';
 import type EvaluationContext from '../evaluation_context';
-import type { Type } from '../types';
 
 // Map input label values to output expression index
 type Cases = {[number | string]: number};
@@ -84,19 +84,25 @@ class Match implements Expression {
             outputs.push(result);
         }
 
-        const input = context.parse(args[1], 1, inputType);
+        const input = context.parse(args[1], 1, ValueType);
         if (!input) return null;
 
         const otherwise = context.parse(args[args.length - 1], args.length - 1, outputType);
         if (!otherwise) return null;
 
         assert(inputType && outputType);
+
+        if (input.type.kind !== 'value' && context.concat(1).checkSubtype((inputType: any), input.type)) {
+            return null;
+        }
+
         return new Match((inputType: any), (outputType: any), input, cases, outputs, otherwise);
     }
 
     evaluate(ctx: EvaluationContext) {
         const input = (this.input.evaluate(ctx): any);
-        return (this.outputs[this.cases[input]] || this.otherwise).evaluate(ctx);
+        const output = (typeOf(input) === this.inputType && this.outputs[this.cases[input]]) || this.otherwise;
+        return output.evaluate(ctx);
     }
 
     eachChild(fn: (Expression) => void) {
@@ -134,7 +140,7 @@ class Match implements Expression {
             }
         }
 
-        const coerceLabel = (label) => this.input.type.kind === 'number' ? Number(label) : label;
+        const coerceLabel = (label) => this.inputType.kind === 'number' ? Number(label) : label;
 
         for (const [outputIndex, labels] of groupedByOutput) {
             if (labels.length === 1) {

src/style-spec/reference/v8.json

@@ -2321,7 +2321,7 @@
         }
       },
       "match": {
-        "doc": "Selects the output whose label value matches the input value, or the fallback value if no match is found. The `input` can be any string or number expression (e.g. `[\"get\", \"building_type\"]`). Each label can either be a single literal value or an array of values.",
+        "doc": "Selects the output whose label value matches the input value, or the fallback value if no match is found. The input can be any expression (e.g. `[\"get\", \"building_type\"]`). Each label must either be a single literal value or an array of literal values (e.g. `\"a\"` or `[\"c\", \"b\"]`), and those values must be all strings or all numbers. (The values `\"1\"` and `1` cannot both be labels in the same match expression.) If the input type does not match the type of the labels, the result will be the fallback value.",
         "group": "Decision",
         "sdk-support": {
           "basic functionality": {

test/integration/expression-tests/match/basic/test.json

@@ -4,7 +4,8 @@
     [{}, {"properties": {"x": "a"}}],
     [{}, {"properties": {"x": "b"}}],
     [{}, {"properties": {"x": "c"}}],
-    [{}, {"properties": {"x": 0}}]
+    [{}, {"properties": {"x": 0}}],
+    [{}, {"properties": {}}]
   ],
   "expected": {
     "compiled": {
@@ -17,13 +18,12 @@
       "Apple",
       "Banana",
       "Kumquat",
-      {
-        "error": "Expected value to be of type string, but found number instead."
-      }
+      "Kumquat",
+      "Kumquat"
     ],
     "serialized": [
       "match",
-      ["string", ["get", "x"]],
+      ["get", "x"],
       "a",
       "Apple",
       "b",

test/integration/expression-tests/match/label-number/test.json

@@ -20,15 +20,11 @@
       "match",
       "otherwise",
       "otherwise",
-      {
-        "error": "Expected value to be of type number, but found string instead."
-      },
-      {
-        "error": "Expected value to be of type number, but found boolean instead."
-      },
-      {"error": "Expected value to be of type number, but found null instead."},
-      {"error": "Expected value to be of type number, but found null instead."}
+      "otherwise",
+      "otherwise",
+      "otherwise",
+      "otherwise"
     ],
-    "serialized": ["match", ["number", ["get", "x"]], 0, "match", "otherwise"]
+    "serialized": ["match", ["get", "x"], 0, "match", "otherwise"]
   }
 }