Add LSIF support

extension/src/basic-code-intel.ts

@@ -0,0 +1,35 @@
+import { Handler, Providers } from '@sourcegraph/basic-code-intel'
+import * as path from 'path'
+import * as sourcegraph from 'sourcegraph'
+
+export function initBasicCodeIntel(): Providers {
+    return new Handler({
+        sourcegraph,
+        languageID: 'typescript',
+        fileExts: ['ts', 'tsx', 'js', 'jsx'],
+        commentStyle: {
+            lineRegex: /\/\/\s?/,
+            block: {
+                startRegex: /\/\*\*?/,
+                lineNoiseRegex: /(^\s*\*\s?)?/,
+                endRegex: /\*\//,
+            },
+        },
+        filterDefinitions: ({ filePath, fileContent, results }) => {
+            const imports = fileContent
+                .split('\n')
+                .map(line => {
+                    // Matches the import at index 1
+                    const match = /\bfrom ['"](.*)['"];?$/.exec(line) || /\brequire\(['"](.*)['"]\)/.exec(line)
+                    return match ? match[1] : undefined
+                })
+                .filter((x): x is string => Boolean(x))
+
+            const filteredResults = results.filter(result =>
+                imports.some(i => path.join(path.dirname(filePath), i) === result.file.replace(/\.[^/.]+$/, ''))
+            )
+
+            return filteredResults.length === 0 ? results : filteredResults
+        },
+    })
+}