perf(table): improve provide/inject performance (addresses #4155)

src/components/table/tbody.js

@@ -19,16 +19,44 @@ export const BTbody = /*#__PURE__*/ Vue.extend({
   inheritAttrs: false,
   provide() {
     return {
-      bvTableTbody: this
+      bvTableRowGroup: this
     }
   },
   inject: {
     bvTable: {
-      default: null
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      default() /* istanbul ignore next */ {
+        return {}
+      }
     }
   },
   props,
   computed: {
+    isTbody() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return true
+    },
+    isDark() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.dark
+    },
+    isStacked() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.isStacked
+    },
+    isResponsive() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.isResponsive
+    },
+    isStickyHeader() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      // Sticky headers are only supported in thead
+      return false
+    },
+    tableVariant() /* istanbul ignore next: Not currently sniffed in tests */ {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.tableVariant
+    },
     isTransitionGroup() {
       return this.tbodyTransitionProps || this.tbodyTransitionHandlers
     },

src/components/table/td.js

@@ -45,21 +45,10 @@ export const BTd = /*#__PURE__*/ Vue.extend({
   mixins: [normalizeSlotMixin],
   inheritAttrs: false,
   inject: {
-    // Injections for feature / attribute detection
-    bvTable: {
-      default: null
-    },
-    bvTableTbody: {
-      default: null
-    },
-    bvTableThead: {
-      default: null
-    },
-    bvTableTfoot: {
-      default: null
-    },
     bvTableTr: {
-      default: null
+      default() /* istanbul ignore next */ {
+        return {}
+      }
     }
   },
   props,
@@ -68,72 +57,82 @@ export const BTd = /*#__PURE__*/ Vue.extend({
       // Overridden by <b-th>
       return 'td'
     },
+    inTbody() {
+      return this.bvTableTr.inTbody
+    },
+    inThead() {
+      return this.bvTableTr.inThead
+    },
+    inTfoot() {
+      return this.bvTableTr.inTfoot
+    },
     isDark() {
-      return this.bvTable && this.bvTable.dark
+      return this.bvTableTr.isDark
     },
     isStacked() {
-      return this.bvTable && this.bvTable.isStacked
+      return this.bvTableTr.isStacked
     },
     isStackedCell() {
       // We only support stacked-heading in tbody in stacked mode
-      return this.bvTableTbody && this.isStacked
+      return this.inTbody && this.isStacked
     },
     isResponsive() {
-      return this.bvTable && this.bvTable.isResponsive && !this.isStacked
+      return this.bvTableTr.isResponsive
     },
     isStickyHeader() {
       // Needed to handle header background classes, due to lack of
       // background color inheritance with Bootstrap v4 table CSS
       // Sticky headers only apply to cells in table `thead`
-      return (
-        !this.isStacked &&
-        this.bvTable &&
-        this.bvTableThead &&
-        this.bvTableTr &&
-        this.bvTable.stickyHeader
-      )
+      return this.bvTableTr.isStickyHeader
     },
     isStickyColumn() {
       // Needed to handle header background classes, due to lack of
       // background color inheritance with Bootstrap v4 table CSS
       // Sticky column cells are only available in responsive
       // mode (horizontal scrolling) or when sticky header mode
       // Applies to cells in `thead`, `tbody` and `tfoot`
-      return (
-        (this.isResponsive || this.isStickyHeader) &&
-        this.stickyColumn &&
-        !this.isStacked &&
-        this.bvTable &&
-        this.bvTableTr
-      )
+      return !this.isStacked && (this.isResponsive || this.isStickyHeader) && this.stickyColumn
+    },
+    rowVariant() {
+      return this.bvTableTr.variant
+    },
+    headVariant() {
+      return this.bvTableTr.headVariant
+    },
+    footVariant() /* istanbul ignore next: need to add in tests for footer variant */ {
+      return this.bvTableTr.footVariant
+    },
+    tableVariant() {
+      return this.bvTableTr.tableVariant
+    },
+    computedColspan() {
+      return parseSpan(this.colspan)
+    },
+    computedRowspan() {
+      return parseSpan(this.rowspan)
     },
     cellClasses() {
       // We use computed props here for improved performance by caching
       // the results of the string interpolation
+      // TODO: need to add handling for footVariant
       let variant = this.variant
       if (
-        (!variant && this.isStickyHeader && !this.bvTableThead.headVariant) ||
+        (!variant && this.isStickyHeader && !this.headVariant) ||
         (!variant && this.isStickyColumn)
       ) {
         // Needed for sticky-header mode as Bootstrap v4 table cells do
         // not inherit parent's background-color. Boo!
-        variant = this.bvTableTr.variant || this.bvTable.tableVariant || 'b-table-default'
+        variant = this.rowVariant || this.tableVariant || 'b-table-default'
       }
       return [
         variant ? `${this.isDark ? 'bg' : 'table'}-${variant}` : null,
         this.isStickyColumn ? 'b-table-sticky-column' : null
       ]
     },
-    computedColspan() {
-      return parseSpan(this.colspan)
-    },
-    computedRowspan() {
-      return parseSpan(this.rowspan)
-    },
     cellAttrs() {
       // We use computed props here for improved performance by caching
       // the results of the object spread (Object.assign)
-      const headOrFoot = this.bvTableThead || this.bvTableTfoot
+      const headOrFoot = this.inThead || this.inTfoot
       // Make sure col/rowspan's are > 0 or null
       const colspan = this.computedColspan
       const rowspan = this.computedRowspan

src/components/table/tfoot.js

@@ -15,16 +15,44 @@ export const BTfoot = /*#__PURE__*/ Vue.extend({
   inheritAttrs: false,
   provide() {
     return {
-      bvTableTfoot: this
+      bvTableRowGroup: this
     }
   },
   inject: {
     bvTable: {
-      default: null
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      default() /* istanbul ignore next */ {
+        return {}
+      }
     }
   },
   props,
   computed: {
+    isTfoot() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return true
+    },
+    isDark() /* istanbul ignore next: Not currently sniffed in tests */ {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.dark
+    },
+    isStacked() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.isStacked
+    },
+    isResponsive() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.isResponsive
+    },
+    isStickyHeader() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      // Sticky headers are only supported in thead
+      return false
+    },
+    tableVariant() /* istanbul ignore next: Not currently sniffed in tests */ {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.tableVariant
+    },
     tfootClasses() {
       return [this.footVariant ? `thead-${this.footVariant}` : null]
     },

src/components/table/thead.js

@@ -3,6 +3,7 @@ import normalizeSlotMixin from '../../mixins/normalize-slot'
 
 export const props = {
   headVariant: {
+    // Also sniffed by <b-tr> / <b-td> / <b-th>
     type: String, // supported values: 'lite', 'dark', or null
     default: null
   }
@@ -15,16 +16,46 @@ export const BThead = /*#__PURE__*/ Vue.extend({
   inheritAttrs: false,
   provide() {
     return {
-      bvTableThead: this
+      bvTableRowGroup: this
     }
   },
   inject: {
     bvTable: {
-      default: null
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      default() /* istanbul ignore next */ {
+        return {}
+      }
     }
   },
   props,
   computed: {
+    isThead() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return true
+    },
+    isDark() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.dark
+    },
+    isStacked() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.isStacked
+    },
+    isResponsive() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.isResponsive
+    },
+    isStickyHeader() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      // Needed to handle header background classes, due to lack of
+      // background color inheritance with Bootstrap v4 table CSS
+      // Sticky headers only apply to cells in table `thead`
+      return !this.isStacked && this.bvTable.stickyHeader
+    },
+    tableVariant() {
+      // Sniffed by <b-tr> / <b-td> / <b-th>
+      return this.bvTable.tableVariant
+    },
     theadClasses() {
       return [this.headVariant ? `thead-${this.headVariant}` : null]
     },

src/components/table/tr.js

@@ -19,14 +19,50 @@ export const BTr = /*#__PURE__*/ Vue.extend({
     }
   },
   inject: {
-    bvTable: {
-      default: null
+    bvTableRowGroup: {
+      defaut() /* istanbul ignore next */ {
+        return {}
+      }
     }
   },
   props,
   computed: {
+    inTbody() {
+      // Sniffed by <b-td> / <b-th>
+      return this.bvTableRowGroup.isTbody
+    },
+    inThead() {
+      // Sniffed by <b-td> / <b-th>
+      return this.bvTableRowGroup.isThead
+    },
+    inTfoot() {
+      // Sniffed by <b-td> / <b-th>
+      return this.bvTableRowGroup.isTfoot
+    },
     isDark() {
-      return this.bvTable && this.bvTable.dark
+      // Sniffed by <b-td> / <b-th>
+      return this.bvTableRowGroup.isDark
+    },
+    isStacked() {
+      // Sniffed by <b-td> / <b-th>
+      return this.bvTableRowGroup.isStacked
+    },
+    isResponsive() {
+      // Sniffed by <b-td> / <b-th>
+      return this.bvTableRowGroup.isResponsive
+    },
+    isStickyHeader() {
+      // Sniffed by <b-td> / <b-th>
+      // Sticky headers are only supported in thead
+      return this.bvTableRowGroup.isStickyHeader
+    },
+    tableVariant() {
+      // Sniffed by <b-td> / <b-th>
+      return this.bvTableRowGroup.tableVariant
+    },
+    headVariant() {
+      // Sniffed by <b-td> / <b-th>
+      return this.bvTableRowGroup.headVariant
     },
     trClasses() {
       return [this.variant ? `${this.isDark ? 'bg' : 'table'}-${this.variant}` : null]