fix(ivy): unable to project into multiple slots with default selector (angular#30561)

With View engine it was possible to declare multiple projection
definitions and to programmatically project nodes into the slots.

e.g.

```html
<ng-content></ng-content>
<ng-content></ng-content>
```

Using `ViewContainerRef#createComponent` allowed projecting
nodes into one of the projection defs (through index)

This no longer works with Ivy as the `projectionDef` instruction only
retrieves a list of selectors instead of also retrieving entries for
reserved projection slots which appear when using the default
selector multiple times (as seen above).

In order to fix this issue, the Ivy compiler now passes all
projection slots to the `projectionDef` instruction. Meaning that
there can be multiple projection slots with the same wildcard
selector. This allows multi-slot projection as seen in the
example above, and it also allows us to match the multi-slot node
projection order from View Engine (to avoid breaking changes).

It basically ensures that Ivy fully matches the View Engine behavior
except of a very small edge case that has already been discussed
in FW-886 (with the conclusion of working as intended).

Read more here: https://hackmd.io/s/Sy2kQlgTE

PR Close angular#30561

Author: devversion

packages/compiler-cli/test/compliance/r3_compiler_compliance_spec.ts

@@ -1159,7 +1159,7 @@ describe('compiler compliance', () => {
             type: SimpleComponent,
             selectors: [["simple"]],
             factory: function SimpleComponent_Factory(t) { return new (t || SimpleComponent)(); },
-            ngContentSelectors: _c0,
+            ngContentSelectors: $c0$,
             consts: 2,
             vars: 0,
             template:  function SimpleComponent_Template(rf, ctx) {
@@ -1189,10 +1189,10 @@ describe('compiler compliance', () => {
               if (rf & 1) {
                 $r3$.ɵɵprojectionDef($c1$);
                 $r3$.ɵɵelementStart(0, "div", $c3$);
-                $r3$.ɵɵprojection(1, 1);
+                $r3$.ɵɵprojection(1);
                 $r3$.ɵɵelementEnd();
                 $r3$.ɵɵelementStart(2, "div", $c4$);
-                $r3$.ɵɵprojection(3, 2);
+                $r3$.ɵɵprojection(3, 1);
                 $r3$.ɵɵelementEnd();
               }
             },
@@ -1209,6 +1209,54 @@ describe('compiler compliance', () => {
             result.source, ComplexComponentDefinition, 'Incorrect ComplexComponent definition');
       });
 
+      it('should support multi-slot content projection with multiple wildcard slots', () => {
+        const files = {
+          app: {
+            'spec.ts': `
+              import {Component, NgModule} from '@angular/core';
+
+              @Component({
+                template: \`
+                  <ng-content></ng-content>
+                  <ng-content select="[spacer]"></ng-content>
+                  <ng-content></ng-content>
+                \`,
+              })
+              class Cmp {}
+
+              @NgModule({ declarations: [Cmp] })
+              class Module {}
+            `,
+          }
+        };
+
+        const output = `
+          const $c0$ = ["*", [["", "spacer", ""]], "*"];
+          const $c1$ = ["*", "[spacer]", "*"];
+          …
+          Cmp.ngComponentDef = $r3$.ɵɵdefineComponent({
+            type: Cmp,
+            selectors: [["ng-component"]],
+            factory: function Cmp_Factory(t) { return new (t || Cmp)(); },
+            ngContentSelectors: $c1$,
+            consts: 3,
+            vars: 0,
+            template: function Cmp_Template(rf, ctx) {
+              if (rf & 1) {
+                i0.ɵɵprojectionDef($c0$);
+                i0.ɵɵprojection(0);
+                i0.ɵɵprojection(1, 1);
+                i0.ɵɵprojection(2, 2);
+              }
+            },
+            encapsulation: 2
+          });
+        `;
+
+        const {source} = compile(files, angularFiles);
+        expectEmit(source, output, 'Invalid content projection instructions generated');
+      });
+
       it('should support content projection in nested templates', () => {
         const files = {
           app: {
@@ -1241,7 +1289,7 @@ describe('compiler compliance', () => {
           const $_c2$ = ["id", "second"];
           function Cmp_div_0_Template(rf, ctx) { if (rf & 1) {
             $r3$.ɵɵelementStart(0, "div", $_c2$);
-            $r3$.ɵɵprojection(1, 1);
+            $r3$.ɵɵprojection(1);
             $r3$.ɵɵelementEnd();
           } }
           const $_c3$ = ["id", "third"];
@@ -1255,10 +1303,10 @@ describe('compiler compliance', () => {
           function Cmp_ng_template_2_Template(rf, ctx) {
             if (rf & 1) {
               $r3$.ɵɵtext(0, " '*' selector: ");
-              $r3$.ɵɵprojection(1);
+              $r3$.ɵɵprojection(1, 1);
             }
           }
-          const $_c4$ = [[["span", "title", "tofirst"]]];
+          const $_c4$ = [[["span", "title", "tofirst"]], "*"];
           …
           template: function Cmp_Template(rf, ctx) {
             if (rf & 1) {
@@ -1312,31 +1360,31 @@ describe('compiler compliance', () => {
         const output = `
           function Cmp_ng_template_1_ng_template_1_Template(rf, ctx) {
               if (rf & 1) {
-                $r3$.ɵɵprojection(0, 4);
+                $r3$.ɵɵprojection(0, 3);
             }
           }
           function Cmp_ng_template_1_Template(rf, ctx) {
             if (rf & 1) {
-              $r3$.ɵɵprojection(0, 3);
+              $r3$.ɵɵprojection(0, 2);
               $r3$.ɵɵtemplate(1, Cmp_ng_template_1_ng_template_1_Template, 1, 0, "ng-template");
             }
           }
           function Cmp_ng_template_2_Template(rf, ctx) {
             if (rf & 1) {
               $r3$.ɵɵtext(0, " '*' selector in a template: ");
-              $r3$.ɵɵprojection(1);
+              $r3$.ɵɵprojection(1, 4);
             }
           }
-          const $_c0$ = [[["", "id", "tomainbefore"]], [["", "id", "tomainafter"]], [["", "id", "totemplate"]], [["", "id", "tonestedtemplate"]]];
-          const $_c1$ = ["[id=toMainBefore]", "[id=toMainAfter]", "[id=toTemplate]", "[id=toNestedTemplate]"];
+          const $_c0$ = [[["", "id", "tomainbefore"]], [["", "id", "tomainafter"]], [["", "id", "totemplate"]], [["", "id", "tonestedtemplate"]], "*"];
+          const $_c1$ = ["[id=toMainBefore]", "[id=toMainAfter]", "[id=toTemplate]", "[id=toNestedTemplate]", "*"];
           …
           template: function Cmp_Template(rf, ctx) {
             if (rf & 1) {
-              $r3$.ɵɵprojectionDef($_c2$);
-              $r3$.ɵɵprojection(0, 1);
+              $r3$.ɵɵprojectionDef($_c0$);
+              $r3$.ɵɵprojection(0);
               $r3$.ɵɵtemplate(1, Cmp_ng_template_1_Template, 2, 0, "ng-template");
               $r3$.ɵɵtemplate(2, Cmp_ng_template_2_Template, 2, 0, "ng-template");
-              $r3$.ɵɵprojection(3, 2);
+              $r3$.ɵɵprojection(3, 1);
             }
           }
         `;

packages/compiler-cli/test/ngtsc/template_mapping_spec.ts

@@ -332,15 +332,15 @@ describe('template source-mapping', () => {
             {source: '<h3>', generated: 'i0.ɵɵelementStart(0, "h3")', sourceUrl: '../test.ts'});
         expect(mappings).toContain({
           source: '<ng-content select="title">',
-          generated: 'i0.ɵɵprojection(1, 1)',
+          generated: 'i0.ɵɵprojection(1)',
           sourceUrl: '../test.ts'
         });
         expect(mappings).toContain(
             {source: '</h3>', generated: 'i0.ɵɵelementEnd()', sourceUrl: '../test.ts'});
         expect(mappings).toContain(
             {source: '<div>', generated: 'i0.ɵɵelementStart(2, "div")', sourceUrl: '../test.ts'});
         expect(mappings).toContain(
-            {source: '<ng-content>', generated: 'i0.ɵɵprojection(3)', sourceUrl: '../test.ts'});
+            {source: '<ng-content>', generated: 'i0.ɵɵprojection(3, 1)', sourceUrl: '../test.ts'});
         expect(mappings).toContain(
             {source: '</div>', generated: 'i0.ɵɵelementEnd()', sourceUrl: '../test.ts'});
       });

packages/compiler/src/render3/view/template.ts

@@ -40,9 +40,6 @@ import {Instruction, StylingBuilder} from './styling_builder';
 import {CONTEXT_NAME, IMPLICIT_REFERENCE, NON_BINDABLE_ATTR, REFERENCE_PREFIX, RENDER_FLAGS, asLiteral, getAttrsForDirectiveMatching, invalid, trimTrailingNulls, unsupported} from './util';
 
 
-// Default selector used by `<ng-content>` if none specified
-const DEFAULT_NG_CONTENT_SELECTOR = '*';
-
 // Selector attribute name of `<ng-content>`
 const NG_CONTENT_SELECT_ATTR = 'select';
 
@@ -146,14 +143,13 @@ export class TemplateDefinitionBuilder implements t.Visitor<void>, LocalResolver
 
   private fileBasedI18nSuffix: string;
 
-  // Whether the template includes <ng-content> tags.
-  private _hasNgContent: boolean = false;
-
-  // Selectors found in the <ng-content> tags in the template.
-  private _ngContentSelectors: string[] = [];
+  // Projection slots found in the template. Projection slots can distribute projected
+  // nodes based on a selector, or can just use the wildcard selector to match
+  // all nodes which aren't matching any selector.
+  private _ngContentReservedSlots: (string|'*')[] = [];
 
   // Number of non-default selectors found in all parent templates of this template. We need to
-  // track it to properly adjust projection bucket index in the `projection` instruction.
+  // track it to properly adjust projection slot index in the `projection` instruction.
   private _ngContentSelectorsOffset = 0;
 
   constructor(
@@ -247,16 +243,19 @@ export class TemplateDefinitionBuilder implements t.Visitor<void>, LocalResolver
     // instructions can be generated with the correct internal const count.
     this._nestedTemplateFns.forEach(buildTemplateFn => buildTemplateFn());
 
-    // Output the `projectionDef` instruction when some `<ng-content>` are present.
-    // The `projectionDef` instruction only emitted for the component template and it is skipped for
-    // nested templates (<ng-template> tags).
-    if (this.level === 0 && this._hasNgContent) {
+    // Output the `projectionDef` instruction when some `<ng-content>` tags are present.
+    // The `projectionDef` instruction is only emitted for the component template and
+    // is skipped for nested templates (<ng-template> tags).
+    if (this.level === 0 && this._ngContentReservedSlots.length) {
       const parameters: o.Expression[] = [];
 
-      // Only selectors with a non-default value are generated
-      if (this._ngContentSelectors.length) {
-        const r3Selectors = this._ngContentSelectors.map(s => core.parseSelectorToR3Selector(s));
-        parameters.push(this.constantPool.getConstLiteral(asLiteral(r3Selectors), true));
+      // By default the `projectionDef` instructions creates one slot for the wildcard
+      // selector if no parameters are passed. Therefore we only want to allocate a new
+      // array for the projection slots if the default projection slot is not sufficient.
+      if (this._ngContentReservedSlots.length > 1 || this._ngContentReservedSlots[0] !== '*') {
+        const r3ReservedSlots = this._ngContentReservedSlots.map(
+            s => s !== '*' ? core.parseSelectorToR3Selector(s) : s);
+        parameters.push(this.constantPool.getConstLiteral(asLiteral(r3ReservedSlots), true));
       }
 
       // Since we accumulate ngContent selectors while processing template elements,
@@ -461,14 +460,13 @@ export class TemplateDefinitionBuilder implements t.Visitor<void>, LocalResolver
   }
 
   visitContent(ngContent: t.Content) {
-    this._hasNgContent = true;
     const slot = this.allocateDataSlot();
-    let selectorIndex = ngContent.selector === DEFAULT_NG_CONTENT_SELECTOR ?
-        0 :
-        this._ngContentSelectors.push(ngContent.selector) + this._ngContentSelectorsOffset;
+    const projectionSlotIdx = this._ngContentSelectorsOffset + this._ngContentReservedSlots.length;
     const parameters: o.Expression[] = [o.literal(slot)];
     const attributes: o.Expression[] = [];
 
+    this._ngContentReservedSlots.push(ngContent.selector);
+
     ngContent.attributes.forEach((attribute) => {
       const {name, value} = attribute;
       if (name === NG_PROJECT_AS_ATTR_NAME) {
@@ -479,9 +477,9 @@ export class TemplateDefinitionBuilder implements t.Visitor<void>, LocalResolver
     });
 
     if (attributes.length > 0) {
-      parameters.push(o.literal(selectorIndex), o.literalArr(attributes));
-    } else if (selectorIndex !== 0) {
-      parameters.push(o.literal(selectorIndex));
+      parameters.push(o.literal(projectionSlotIdx), o.literalArr(attributes));
+    } else if (projectionSlotIdx !== 0) {
+      parameters.push(o.literal(projectionSlotIdx));
     }
 
     this.creationInstruction(ngContent.sourceSpan, R3.projection, parameters);
@@ -887,11 +885,10 @@ export class TemplateDefinitionBuilder implements t.Visitor<void>, LocalResolver
     this._nestedTemplateFns.push(() => {
       const templateFunctionExpr = templateVisitor.buildTemplateFunction(
           template.children, template.variables,
-          this._ngContentSelectors.length + this._ngContentSelectorsOffset, template.i18n);
+          this._ngContentReservedSlots.length + this._ngContentSelectorsOffset, template.i18n);
       this.constantPool.statements.push(templateFunctionExpr.toDeclStmt(templateName, null));
-      if (templateVisitor._hasNgContent) {
-        this._hasNgContent = true;
-        this._ngContentSelectors.push(...templateVisitor._ngContentSelectors);
+      if (templateVisitor._ngContentReservedSlots.length) {
+        this._ngContentReservedSlots.push(...templateVisitor._ngContentReservedSlots);
       }
     });
 
@@ -1011,8 +1008,8 @@ export class TemplateDefinitionBuilder implements t.Visitor<void>, LocalResolver
   getVarCount() { return this._pureFunctionSlots; }
 
   getNgContentSelectors(): o.Expression|null {
-    return this._hasNgContent ?
-        this.constantPool.getConstLiteral(asLiteral(this._ngContentSelectors), true) :
+    return this._ngContentReservedSlots.length ?
+        this.constantPool.getConstLiteral(asLiteral(this._ngContentReservedSlots), true) :
         null;
   }
 

packages/core/src/render3/component_ref.ts

@@ -123,10 +123,8 @@ export class ComponentFactory<T> extends viewEngine_ComponentFactory<T> {
     super();
     this.componentType = componentDef.type;
     this.selector = componentDef.selectors[0][0] as string;
-    // The component definition does not include the wildcard ('*') selector in its list.
-    // It is implicitly expected as the first item in the projectable nodes array.
     this.ngContentSelectors =
-        componentDef.ngContentSelectors ? ['*', ...componentDef.ngContentSelectors] : [];
+        componentDef.ngContentSelectors ? componentDef.ngContentSelectors : [];
     this.isBoundToModule = !!ngModule;
   }
 

packages/core/src/render3/index.ts

@@ -121,7 +121,7 @@ export {
   ɵɵtextInterpolateV,
 } from './instructions/all';
 export {RenderFlags} from './interfaces/definition';
-export {CssSelectorList} from './interfaces/projection';
+export {CssSelectorList, ProjectionSlots} from './interfaces/projection';
 
 export {
   ɵɵrestoreView,

packages/core/src/render3/instructions/projection.ts

@@ -5,18 +5,47 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-import {assertDataInRange} from '../../util/assert';
 import {TAttributes, TElementNode, TNode, TNodeType} from '../interfaces/node';
-import {CssSelectorList} from '../interfaces/projection';
-import {HEADER_OFFSET, TVIEW, T_HOST} from '../interfaces/view';
+import {ProjectionSlots} from '../interfaces/projection';
+import {TVIEW, T_HOST} from '../interfaces/view';
 import {appendProjectedNodes} from '../node_manipulation';
-import {matchingProjectionSelectorIndex} from '../node_selector_matcher';
+import {getProjectAsAttrValue, isNodeMatchingSelectorList, isSelectorInSelectorList} from '../node_selector_matcher';
 import {getLView, setIsNotParent} from '../state';
 import {findComponentView} from '../util/view_traversal_utils';
 
 import {getOrCreateTNode} from './shared';
 
 
+/**
+ * Checks a given node against matching projection slots and returns the
+ * determined slot index. Returns "null" if no slot matched the given node.
+ *
+ * This function takes into account the parsed ngProjectAs selector from the
+ * node's attributes. If present, it will check whether the ngProjectAs selector
+ * matches any of the projection slot selectors.
+ */
+export function matchingProjectionSlotIndex(tNode: TNode, projectionSlots: ProjectionSlots): number|
+    null {
+  let wildcardNgContentIndex = null;
+  const ngProjectAsAttrVal = getProjectAsAttrValue(tNode);
+  for (let i = 0; i < projectionSlots.length; i++) {
+    const slotValue = projectionSlots[i];
+    // The last wildcard projection slot should match all nodes which aren't matching
+    // any selector. This is necessary to be backwards compatible with view engine.
+    if (slotValue === '*') {
+      wildcardNgContentIndex = i;
+      continue;
+    }
+    // If we ran into an `ngProjectAs` attribute, we should match its parsed selector
+    // to the list of selectors, otherwise we fall back to matching against the node.
+    if (ngProjectAsAttrVal === null ?
+            isNodeMatchingSelectorList(tNode, slotValue, /* isProjectionMode */ true) :
+            isSelectorInSelectorList(ngProjectAsAttrVal, slotValue)) {
+      return i;  // first matching selector "captures" a given node
+    }
+  }
+  return wildcardNgContentIndex;
+}
 
 /**
  * Instruction to distribute projectable nodes among <ng-content> occurrences in a given template.
@@ -36,32 +65,38 @@ import {getOrCreateTNode} from './shared';
  * - we can't have only a parsed as we can't re-construct textual form from it (as entered by a
  * template author).
  *
- * @param selectors A collection of parsed CSS selectors
- * @param rawSelectors A collection of CSS selectors in the raw, un-parsed form
+ * @param projectionSlots? A collection of projection slots. A projection slot can be based
+ *        on a parsed CSS selectors or set to the wildcard selector ("*") in order to match
+ *        all nodes which do not match any selector. If not specified, a single wildcard
+ *        selector projection slot will be defined.
  *
  * @codeGenApi
  */
-export function ɵɵprojectionDef(selectors?: CssSelectorList[]): void {
+export function ɵɵprojectionDef(projectionSlots?: ProjectionSlots): void {
   const componentNode = findComponentView(getLView())[T_HOST] as TElementNode;
 
   if (!componentNode.projection) {
-    const noOfNodeBuckets = selectors ? selectors.length + 1 : 1;
+    // If no explicit projection slots are defined, fall back to a single
+    // projection slot with the wildcard selector.
+    const numProjectionSlots = projectionSlots ? projectionSlots.length : 1;
     const projectionHeads: (TNode | null)[] = componentNode.projection =
-        new Array(noOfNodeBuckets).fill(null);
+        new Array(numProjectionSlots).fill(null);
     const tails: (TNode | null)[] = projectionHeads.slice();
 
     let componentChild: TNode|null = componentNode.child;
 
     while (componentChild !== null) {
-      const bucketIndex =
-          selectors ? matchingProjectionSelectorIndex(componentChild, selectors) : 0;
+      const slotIndex =
+          projectionSlots ? matchingProjectionSlotIndex(componentChild, projectionSlots) : 0;
 
-      if (tails[bucketIndex]) {
-        tails[bucketIndex] !.projectionNext = componentChild;
-      } else {
-        projectionHeads[bucketIndex] = componentChild;
+      if (slotIndex !== null) {
+        if (tails[slotIndex]) {
+          tails[slotIndex] !.projectionNext = componentChild;
+        } else {
+          projectionHeads[slotIndex] = componentChild;
+        }
+        tails[slotIndex] = componentChild;
       }
-      tails[bucketIndex] = componentChild;
 
       componentChild = componentChild.next;
     }