Replace no-op style filter expressions (#62)

* replace noop expressions

* update changelog

* 0.3.3-pre [publish binary]

* further simplify case if possible

* add more edge case, rename function

* even more aggressive – don't look into inner branches

* Revert "even more aggressive – don't look into inner branches"

This reverts commit dfc71e7.

* flush at all or any

* 0.3.3-pre2 [publish binary]

* 0.3.3 [publish binary]

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog
 
+## v0.3.3
+- Replace no-op style filter expressions with `true` [#62](https://github.com/mapbox/vtshaver/pull/62).
+
 ## v0.3.2
 - Add missing symbol implementations for `downcase`, `upcase`, and `number-formatter` expressions. The implementation for `number-formatter` is a basic `to_string` and uses no config options. [#58](https://github.com/mapbox/vtshaver/pull/58)
 

lib/styleToFilters.js

@@ -36,17 +36,23 @@ function styleToFilters(style) {
           if (layers[layerName].filters === true || !style.layers[i].filter) {
             layers[layerName].filters = true;
           } else {
-            layers[layerName].filters.push(style.layers[i].filter);
+            let filter = replaceNoOpExpressions(style.layers[i].filter);
+            layers[layerName].filters.push(filter === 'noop' ? ['literal', true] : filter);
           }
         } else {
           // otherwise create the layer & filter array, with min/max zoom
           layers[layerName] = {};
-          layers[layerName].filters = style.layers[i].filter ? ['any', style.layers[i].filter] : true;
+          if (style.layers[i].filter) {
+            let filter = replaceNoOpExpressions(style.layers[i].filter);
+            layers[layerName].filters = ['any', filter === 'noop' ? ['literal', true] : filter]
+          } else {
+            layers[layerName].filters = true;
+          }
           layers[layerName].minzoom = style.layers[i].minzoom || 0;
           layers[layerName].maxzoom = style.layers[i].maxzoom || 22;
         }
 
-        // Collect the used properties 
+        // Collect the used properties
         // 1. from paint, layout, and filter
         layers[layerName].properties = layers[layerName].properties || [];
         ['paint', 'layout'].forEach(item => {
@@ -105,7 +111,6 @@ function getPropertyFromFilter(filter, properties) {
       if (filter[1].indexOf('$') === -1) {
         properties.push(filter[1]);
       }
-
     }
   }
   // }
@@ -143,6 +148,31 @@ function getPropertyFromLayoutAndPainter(propertyObj, properties) {
 }
 
 
+function replaceNoOpExpressions(exp) {
+  if (exp instanceof Array) {
+    switch (exp[0]) {
+      case 'pitch':
+      case 'distance-from-center':
+        return 'noop';
+    }
+
+    let newExp = exp.map(sub => sub instanceof Array ? replaceNoOpExpressions(sub) : sub);
+
+    if (newExp.includes('noop')) {
+      switch (newExp[0]) {
+        case 'any':
+        case 'all':
+          return newExp.map(sub => sub === 'noop' ? ['literal', true] : sub);
+        default:
+          return 'noop';
+      }
+    }
+    else return newExp;
+  }
+  else return exp;
+}
+
+
 function getPropertyFromExpression(exp, properties) {
   // now we care about the expression like:
   // ["get", string] not ["get", string, Object],
@@ -173,4 +203,4 @@ function getPropertyFromExpression(exp, properties) {
   }
 }
 
-module.exports = styleToFilters;
+module.exports = styleToFilters;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mapbox/vtshaver",
-  "version": "0.3.2",
+  "version": "0.3.3",
   "description": "Creates style-optimized vector tiles",
   "main": "./lib/index.js",
   "repository": {

test/fixtures/styles/cafe.json

@@ -1,7 +1,7 @@
 {
 	"version": 1,
 	"name": "cafe",
-	"center": [ 
+	"center": [
 	    -122.51238479904751,
 	    37.77981694417855
 	],
@@ -15,7 +15,19 @@
 			"source": "composite",
 			"id": "poi-scalerank1",
 			"source-layer": "poi_label"
+		},
+		{
+			"filter": [
+              "all",
+			  ["==","maki","cafe"],
+			  ["<=", ["pitch"], 45],
+			  ["<=", ["distance-from-center"], 1]
+            ],
+			"type": "symbol",
+			"source": "composite",
+			"id": "poi-landmarks",
+			"source-layer": "poi_label"
 		}
 	],
 	"owner": "greta"
-}
+}

test/styleToFilter.test.js

@@ -128,14 +128,67 @@ test('simple style layers', function(t) {
   t.deepEqual(styleToFilter({
     layers: [{
         'source-layer': 'water',
-        filter: ['!=', 'color', 'blue']
+        filter: [
+          'all',
+          [
+            'case',
+            ['>=', ['distance-from-center'], 5],  // test no-op in case condition
+            false,
+            ['>=', ['pitch'], 45],
+            false,
+            true
+          ],
+          [
+            'match',
+            ['get', 'distance'],
+            [1, 4, ['distance-from-center']],  // test no-op in match value
+            false,
+            true
+          ],
+          [
+            'coalesce',
+            ['get', 'display'],
+            ['>=', ['distance-from-center'], 3]  // test no-op in coalesce
+          ],
+          [
+            'any',
+            ['boolean', false],
+            ['>=', ['pitch'], 5]  // test no-op in any
+          ],
+          [
+            'all',
+            ['boolean', true],
+            ['<', ['pitch'], 5]  // test no-op in all
+          ],
+          ['==', 'color', 'blue']
+        ]
       },
       {
         'source-layer': 'landcover',
-        filter: ['==', 'color', 'blue']
+        filter: [
+          '>=',
+          ['distance-from-center'],
+          [
+            'case',
+            ['==', 'color', 'blue'],
+            2,
+            4
+          ]
+        ]
+      },
+      {
+        'source-layer': 'landuse_overlay',
+        filter: [
+          'case',
+          ['<=', ['pitch'], 10],
+          ['==', ['distance-from-center'], 4],  // test no-op in value
+          ['to-boolean', ['get', 'display']],
+          true,
+          false
+        ]
       }
     ]
-  }), { water: { filters: ['any', ['!=', 'color', 'blue']], minzoom: 0, maxzoom: 22, properties: ['color'] }, landcover: { filters: ['any', ['==', 'color', 'blue']], minzoom: 0, maxzoom: 22, properties: ['color'] } }, 'returns right filters for multiple layers with filters');
+}), { water: { filters: ['any', ['all', ['literal', true], ['literal', true], ['literal', true], ['any', ['boolean', false], ['literal', true]], ['all', ['boolean', true], ['literal', true]], ['==', 'color', 'blue']]], minzoom: 0, maxzoom: 22, properties: ['distance', 'display', 'color'] }, landcover: { filters: ['any', ['literal', true]], minzoom: 0, maxzoom: 22, properties: ['color'] }, landuse_overlay: { filters: ['any', ['literal', true]], minzoom: 0, maxzoom: 22, properties: ['display'] } }, 'returns right filters for no-op expressions');
 
   t.end();
 });
@@ -173,4 +226,4 @@ test('v8 streets style with legacy+expressions filter combo', function(t) {
   t.deepEquals(filters, require(filter_result_expressions), 'expressions filter is extracted correctly');
 
   t.end();
-});
+});