An import ending in "/" is always an import of a directory.

src/compiler/core.ts

@@ -829,8 +829,20 @@ namespace ts {
     export function normalizePath(path: string): string {
         path = normalizeSlashes(path);
         const rootLength = getRootLength(path);
+        const root = path.substr(0, rootLength);
         const normalized = getNormalizedParts(path, rootLength);
-        return path.substr(0, rootLength) + normalized.join(directorySeparator);
+        if (normalized.length) {
+            const joinedParts = root + normalized.join(directorySeparator);
+            return isPathToDirectory(path) ? joinedParts + "/" : joinedParts;
+        }
+        else {
+            return root;
+        }
+    }
+
+    /** A path ending with '/' refers to a directory only, never a file. */
+    export function isPathToDirectory(path: string): boolean {
+        return path.charCodeAt(path.length - 1) === CharacterCodes.slash;
     }
 
     export function getDirectoryPath(path: Path): Path;

src/compiler/program.ts

@@ -646,7 +646,7 @@ namespace ts {
             trace(state.host, Diagnostics.Loading_module_as_file_Slash_folder_candidate_module_location_0, candidate);
         }
 
-        const resolvedFileName = loadModuleFromFile(candidate, supportedExtensions, failedLookupLocations, onlyRecordFailures, state);
+        const resolvedFileName = !isPathToDirectory(candidate) && loadModuleFromFile(candidate, supportedExtensions, failedLookupLocations, onlyRecordFailures, state);
 
         return resolvedFileName || loadNodeModuleFromDirectory(supportedExtensions, candidate, failedLookupLocations, onlyRecordFailures, state);
     }

tests/baselines/reference/pathMappingBasedModuleResolution7_classic.trace.json

@@ -14,7 +14,7 @@
     "======== Module name './project/file2' was successfully resolved to 'c:/root/generated/src/project/file2.ts'. ========",
     "======== Resolving module 'module3' from 'c:/root/src/file1.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
-    "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'module3'",
+    "'baseUrl' option is set to 'c:/root/', using this value to resolve non-relative module name 'module3'",
     "'paths' option is specified, looking for a pattern to match module name 'module3'.",
     "Module name 'module3', matched pattern '*'.",
     "Trying substitution '*', candidate module location: 'module3'.",
@@ -32,7 +32,7 @@
     "======== Module name 'module3' was successfully resolved to 'c:/module3.d.ts'. ========",
     "======== Resolving module 'module1' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
-    "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'module1'",
+    "'baseUrl' option is set to 'c:/root/', using this value to resolve non-relative module name 'module1'",
     "'paths' option is specified, looking for a pattern to match module name 'module1'.",
     "Module name 'module1', matched pattern '*'.",
     "Trying substitution '*', candidate module location: 'module1'.",
@@ -44,7 +44,7 @@
     "======== Module name 'module1' was successfully resolved to 'c:/shared/module1.d.ts'. ========",
     "======== Resolving module 'templates/module2' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
-    "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'templates/module2'",
+    "'baseUrl' option is set to 'c:/root/', using this value to resolve non-relative module name 'templates/module2'",
     "'paths' option is specified, looking for a pattern to match module name 'templates/module2'.",
     "Module name 'templates/module2', matched pattern 'templates/*'.",
     "Trying substitution 'generated/src/templates/*', candidate module location: 'generated/src/templates/module2'.",

tests/baselines/reference/pathMappingBasedModuleResolution7_node.trace.json

@@ -22,7 +22,7 @@
     "======== Module name './project/file2' was successfully resolved to 'c:/root/generated/src/project/file2.ts'. ========",
     "======== Resolving module 'module3' from 'c:/root/src/file1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
-    "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'module3'",
+    "'baseUrl' option is set to 'c:/root/', using this value to resolve non-relative module name 'module3'",
     "'paths' option is specified, looking for a pattern to match module name 'module3'.",
     "Module name 'module3', matched pattern '*'.",
     "Trying substitution '*', candidate module location: 'module3'.",
@@ -79,7 +79,7 @@
     "======== Module name 'module3' was successfully resolved to 'c:/node_modules/module3.d.ts'. ========",
     "======== Resolving module 'module1' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
-    "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'module1'",
+    "'baseUrl' option is set to 'c:/root/', using this value to resolve non-relative module name 'module1'",
     "'paths' option is specified, looking for a pattern to match module name 'module1'.",
     "Module name 'module1', matched pattern '*'.",
     "Trying substitution '*', candidate module location: 'module1'.",
@@ -104,7 +104,7 @@
     "======== Module name 'module1' was successfully resolved to 'c:/shared/module1/index.d.ts'. ========",
     "======== Resolving module 'templates/module2' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
-    "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'templates/module2'",
+    "'baseUrl' option is set to 'c:/root/', using this value to resolve non-relative module name 'templates/module2'",
     "'paths' option is specified, looking for a pattern to match module name 'templates/module2'.",
     "Module name 'templates/module2', matched pattern 'templates/*'.",
     "Trying substitution 'generated/src/templates/*', candidate module location: 'generated/src/templates/module2'.",

tests/baselines/reference/relativeModuleWithoutSlash.js

@@ -11,13 +11,13 @@ export default { aIndex: 0 };
 import a from ".";
 import aIndex from "./";
 a.a;
-aIndex.a; //aIndex.aIndex; See GH#9690
+aIndex.aIndex;
 
 //// [test.ts]
 import a from "..";
 import aIndex from "../";
 a.a;
-aIndex.a; //aIndex.aIndex;
+aIndex.aIndex;
 
 
 //// [a.js]
@@ -33,10 +33,10 @@ exports["default"] = { aIndex: 0 };
 var _1 = require(".");
 var _2 = require("./");
 _1["default"].a;
-_2["default"].a; //aIndex.aIndex; See GH#9690
+_2["default"].aIndex;
 //// [test.js]
 "use strict";
 var __1 = require("..");
 var _1 = require("../");
 __1["default"].a;
-_1["default"].a; //aIndex.aIndex;
+_1["default"].aIndex;

tests/baselines/reference/relativeModuleWithoutSlash.symbols

@@ -19,10 +19,10 @@ a.a;
 >a : Symbol(a, Decl(test.ts, 0, 6))
 >a : Symbol(a, Decl(a.ts, 1, 16))
 
-aIndex.a; //aIndex.aIndex; See GH#9690
->aIndex.a : Symbol(a, Decl(a.ts, 1, 16))
+aIndex.aIndex;
+>aIndex.aIndex : Symbol(aIndex, Decl(index.ts, 0, 16))
 >aIndex : Symbol(aIndex, Decl(test.ts, 1, 6))
->a : Symbol(a, Decl(a.ts, 1, 16))
+>aIndex : Symbol(aIndex, Decl(index.ts, 0, 16))
 
 === /a/b/test.ts ===
 import a from "..";
@@ -36,8 +36,8 @@ a.a;
 >a : Symbol(a, Decl(test.ts, 0, 6))
 >a : Symbol(a, Decl(a.ts, 1, 16))
 
-aIndex.a; //aIndex.aIndex;
->aIndex.a : Symbol(a, Decl(a.ts, 1, 16))
+aIndex.aIndex;
+>aIndex.aIndex : Symbol(aIndex, Decl(index.ts, 0, 16))
 >aIndex : Symbol(aIndex, Decl(test.ts, 1, 6))
->a : Symbol(a, Decl(a.ts, 1, 16))
+>aIndex : Symbol(aIndex, Decl(index.ts, 0, 16))
 

tests/baselines/reference/relativeModuleWithoutSlash.trace.json

@@ -7,10 +7,11 @@
     "======== Module name '.' was successfully resolved to '/a.ts'. ========",
     "======== Resolving module './' from '/a/test.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
-    "Loading module as file / folder, candidate module location '/a'.",
-    "File '/a.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/a.ts', result '/a.ts'",
-    "======== Module name './' was successfully resolved to '/a.ts'. ========",
+    "Loading module as file / folder, candidate module location '/a/'.",
+    "File '/a/package.json' does not exist.",
+    "File '/a/index.ts' exist - use it as a name resolution result.",
+    "Resolving real path for '/a/index.ts', result '/a/index.ts'",
+    "======== Module name './' was successfully resolved to '/a/index.ts'. ========",
     "======== Resolving module '..' from '/a/b/test.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/a'.",
@@ -19,8 +20,9 @@
     "======== Module name '..' was successfully resolved to '/a.ts'. ========",
     "======== Resolving module '../' from '/a/b/test.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
-    "Loading module as file / folder, candidate module location '/a'.",
-    "File '/a.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/a.ts', result '/a.ts'",
-    "======== Module name '../' was successfully resolved to '/a.ts'. ========"
+    "Loading module as file / folder, candidate module location '/a/'.",
+    "File '/a/package.json' does not exist.",
+    "File '/a/index.ts' exist - use it as a name resolution result.",
+    "Resolving real path for '/a/index.ts', result '/a/index.ts'",
+    "======== Module name '../' was successfully resolved to '/a/index.ts'. ========"
 ]

tests/baselines/reference/relativeModuleWithoutSlash.types

@@ -16,32 +16,32 @@ import a from ".";
 >a : { a: number; }
 
 import aIndex from "./";
->aIndex : { a: number; }
+>aIndex : { aIndex: number; }
 
 a.a;
 >a.a : number
 >a : { a: number; }
 >a : number
 
-aIndex.a; //aIndex.aIndex; See GH#9690
->aIndex.a : number
->aIndex : { a: number; }
->a : number
+aIndex.aIndex;
+>aIndex.aIndex : number
+>aIndex : { aIndex: number; }
+>aIndex : number
 
 === /a/b/test.ts ===
 import a from "..";
 >a : { a: number; }
 
 import aIndex from "../";
->aIndex : { a: number; }
+>aIndex : { aIndex: number; }
 
 a.a;
 >a.a : number
 >a : { a: number; }
 >a : number
 
-aIndex.a; //aIndex.aIndex;
->aIndex.a : number
->aIndex : { a: number; }
->a : number
+aIndex.aIndex;
+>aIndex.aIndex : number
+>aIndex : { aIndex: number; }
+>aIndex : number
 

tests/cases/compiler/relativeModuleWithoutSlash.ts

@@ -11,10 +11,10 @@ export default { aIndex: 0 };
 import a from ".";
 import aIndex from "./";
 a.a;
-aIndex.a; //aIndex.aIndex; See GH#9690
+aIndex.aIndex;
 
 // @Filename: /a/b/test.ts
 import a from "..";
 import aIndex from "../";
 a.a;
-aIndex.a; //aIndex.aIndex;
+aIndex.aIndex;