Add assert keyword in completions (microsoft#47644)

* add contextual keyword assert in completions

* clean up

Author: gabritto

src/services/completions.ts

@@ -288,7 +288,7 @@ namespace ts.Completions {
 
         switch (completionData.kind) {
             case CompletionDataKind.Data:
-                const response = completionInfoFromData(sourceFile, host, program, compilerOptions, log, completionData, preferences, formatContext);
+                const response = completionInfoFromData(sourceFile, host, program, compilerOptions, log, completionData, preferences, formatContext, position);
                 if (response?.isIncomplete) {
                     incompleteCompletionsCache?.set(response);
                 }
@@ -452,6 +452,7 @@ namespace ts.Completions {
         completionData: CompletionData,
         preferences: UserPreferences,
         formatContext: formatting.FormatContext | undefined,
+        position: number
     ): CompletionInfo | undefined {
         const {
             symbols,
@@ -512,7 +513,7 @@ namespace ts.Completions {
                 isJsxIdentifierExpected,
                 isRightOfOpenTag,
             );
-            getJSCompletionEntries(sourceFile, location.pos, uniqueNames, getEmitScriptTarget(compilerOptions), entries); // TODO: GH#18217
+            getJSCompletionEntries(sourceFile, location.pos, uniqueNames, getEmitScriptTarget(compilerOptions), entries);
         }
         else {
             if (!isNewIdentifierLocation && (!symbols || symbols.length === 0) && keywordFilters === KeywordCompletionFilters.None) {
@@ -556,6 +557,13 @@ namespace ts.Completions {
             }
         }
 
+        const entryNames = new Set(entries.map(e => e.name));
+        for (const keywordEntry of getContextualKeywords(contextToken, position)) {
+            if (!entryNames.has(keywordEntry.name)) {
+                insertSorted(entries, keywordEntry, compareCompletionEntries, /*allowDuplicates*/ true);
+            }
+        }
+
         for (const literal of literals) {
             insertSorted(entries, createCompletionEntryForLiteral(sourceFile, preferences, literal), compareCompletionEntries, /*allowDuplicates*/ true);
         }
@@ -3630,6 +3638,38 @@ namespace ts.Completions {
         return isIdentifier(node) ? node.originalKeywordKind || SyntaxKind.Unknown : node.kind;
     }
 
+    function getContextualKeywords(
+        contextToken: Node | undefined,
+        position: number,
+    ): readonly CompletionEntry[] {
+        const entries = [];
+        /**
+         * An `AssertClause` can come after an import declaration:
+         *  import * from "foo" |
+         *  import "foo" |
+         * or after a re-export declaration that has a module specifier:
+         *  export { foo } from "foo" |
+         * Source: https://tc39.es/proposal-import-assertions/
+         */
+        if (contextToken) {
+            const file = contextToken.getSourceFile();
+            const parent = contextToken.parent;
+            const tokenLine = file.getLineAndCharacterOfPosition(contextToken.end).line;
+            const currentLine = file.getLineAndCharacterOfPosition(position).line;
+            if ((isImportDeclaration(parent) || isExportDeclaration(parent) && parent.moduleSpecifier)
+                && contextToken === parent.moduleSpecifier
+                && tokenLine === currentLine) {
+                entries.push({
+                    name: tokenToString(SyntaxKind.AssertKeyword)!,
+                    kind: ScriptElementKind.keyword,
+                    kindModifiers: ScriptElementKindModifier.none,
+                    sortText: SortText.GlobalsOrKeywords,
+                });
+            }
+        }
+        return entries;
+    }
+
     /** Get the corresponding JSDocTag node if the position is in a jsDoc comment */
     function getJsDocTagAtPosition(node: Node, position: number): JSDocTag | undefined {
         return findAncestor(node, n =>

tests/cases/fourslash/completionsAssertKeyword.ts

@@ -0,0 +1,54 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+// @Filename: a.ts
+//// const f = {
+////    a: 1
+////};
+//// import * as thing from "thing" /*0*/
+//// export { foo } from "foo" /*1*/
+//// import "foo" as /*2*/
+//// import "foo" a/*3*/
+//// import * as that from "that"
+//// /*4*/
+//// import * /*5*/ as those from "those"
+
+// @Filename: b.js
+//// import * as thing from "thing" /*js*/;
+
+const assertEntry = {
+    name: "assert",
+    kind: "keyword",
+    sortText: completion.SortText.GlobalsOrKeywords,
+};
+
+verify.completions(
+    {
+        marker: "0",
+        includes: [assertEntry],
+    },
+    {
+        marker: "1",
+        includes: [assertEntry],
+    },
+    {
+        marker: "2",
+        excludes: ["assert"],
+    },
+    {
+        marker: "3",
+        includes: [assertEntry],
+    },
+    {
+        marker: "4",
+        excludes: ["assert"],
+    },
+    {
+        marker: "5",
+        excludes: ["assert"],
+    },
+    {
+        marker: "js",
+        includes: [assertEntry],
+    },
+);