Resolve json modules only when --resolveJsonModule is specified

Author: sheetalkamat

src/compiler/commandLineParser.ts

@@ -506,6 +506,12 @@ namespace ts {
             category: Diagnostics.Advanced_Options,
             description: Diagnostics.Enable_tracing_of_the_name_resolution_process
         },
+        {
+            name: "resolveJsonModule",
+            type: "boolean",
+            category: Diagnostics.Advanced_Options,
+            description: Diagnostics.Resolve_module_name_imported_with_json_extension_to_the_json_source_file
+        },
         {
             name: "listFiles",
             type: "boolean",

src/compiler/diagnosticMessages.json

@@ -2795,6 +2795,10 @@
         "category": "Error",
         "code": 5069
     },
+    "Option '--resolveJsonModule' cannot be specified without 'node' module resolution strategy.": {
+        "category": "Error",
+        "code": 5070
+    },
 
     "Generates a sourcemap for each corresponding '.d.ts' file.": {
         "category": "Message",
@@ -3527,6 +3531,11 @@
         "category": "Message",
         "code": 6194
     },
+    "Resolve module name imported with '.json' extension to the json source file.": {
+        "category": "Message",
+        "code": 6195
+    },
+
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005

src/compiler/moduleNameResolver.ts

@@ -743,7 +743,11 @@ namespace ts {
         const failedLookupLocations: string[] = [];
         const state: ModuleResolutionState = { compilerOptions, host, traceEnabled };
 
-        const result = (jsOnly ? tryResolve(Extensions.JavaScript) : (tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript))) || tryResolve(Extensions.Json);
+        const result = jsOnly ?
+            tryResolve(Extensions.JavaScript) :
+            (tryResolve(Extensions.TypeScript) ||
+                tryResolve(Extensions.JavaScript) ||
+                (compilerOptions.resolveJsonModule ? tryResolve(Extensions.Json) : undefined));
         if (result && result.value) {
             const { resolved, originalPath, isExternalLibraryImport } = result.value;
             return createResolvedModuleWithFailedLookupLocations(resolved, originalPath, isExternalLibraryImport, failedLookupLocations);

src/compiler/program.ts

@@ -2195,6 +2195,12 @@ namespace ts {
                 }
             }
 
+            if (options.resolveJsonModule) {
+                if (getEmitModuleResolutionKind(options) !== ModuleResolutionKind.NodeJs) {
+                    createDiagnosticForOptionName(Diagnostics.Option_resolveJsonModule_cannot_be_specified_without_node_module_resolution_strategy, "resolveJsonModule");
+                }
+            }
+
             // there has to be common source directory if user specified --outdir || --sourceRoot
             // if user specified --mapRoot, there needs to be common source directory if there would be multiple files being emitted
             if (options.outDir || // there is --outDir specified

src/compiler/types.ts

@@ -4220,6 +4220,7 @@ namespace ts {
         /* @internal */ suppressOutputPathCheck?: boolean;
         target?: ScriptTarget;
         traceResolution?: boolean;
+        resolveJsonModule?: boolean;
         types?: string[];
         /** Paths used to compute primary types search locations */
         typeRoots?: string[];

src/harness/unittests/reuseProgramStructure.ts

@@ -471,8 +471,6 @@ namespace ts {
                         "File 'node_modules/a.jsx' does not exist.",
                         "File 'node_modules/a/index.js' does not exist.",
                         "File 'node_modules/a/index.jsx' does not exist.",
-                        "Loading module 'a' from 'node_modules' folder, target file type 'Json'.",
-                        "File 'node_modules/a/package.json' does not exist.",
                         "======== Module name 'a' was not resolved. ========"
                     ],
                     "initialProgram: execute module resolution normally.");

src/harness/unittests/tsserverProjectSystem.ts

@@ -3386,10 +3386,6 @@ namespace ts.projectSystem {
                 "Directory '/a/b/node_modules' does not exist, skipping all lookups in it.",
                 "Directory '/a/node_modules' does not exist, skipping all lookups in it.",
                 "Directory '/node_modules' does not exist, skipping all lookups in it.",
-                "Loading module 'lib' from 'node_modules' folder, target file type 'Json'.",
-                "Directory '/a/b/node_modules' does not exist, skipping all lookups in it.",
-                "Directory '/a/node_modules' does not exist, skipping all lookups in it.",
-                "Directory '/node_modules' does not exist, skipping all lookups in it.",
                 "======== Module name 'lib' was not resolved. ========",
                 `Auto discovery for typings is enabled in project '${proj.getProjectName()}'. Running extra resolution pass for module 'lib' using cache location '/a/cache'.`,
                 "File '/a/cache/node_modules/lib.d.ts' does not exist.",

src/server/protocol.ts

@@ -2716,6 +2716,7 @@ namespace ts.server.protocol {
         suppressImplicitAnyIndexErrors?: boolean;
         target?: ScriptTarget | ts.ScriptTarget;
         traceResolution?: boolean;
+        resolveJsonModule?: boolean;
         types?: string[];
         /** Paths used to used to compute primary types search locations */
         typeRoots?: string[];

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -2390,6 +2390,7 @@ declare namespace ts {
         suppressImplicitAnyIndexErrors?: boolean;
         target?: ScriptTarget;
         traceResolution?: boolean;
+        resolveJsonModule?: boolean;
         types?: string[];
         /** Paths used to compute primary types search locations */
         typeRoots?: string[];
@@ -7239,6 +7240,7 @@ declare namespace ts.server.protocol {
         suppressImplicitAnyIndexErrors?: boolean;
         target?: ScriptTarget | ts.ScriptTarget;
         traceResolution?: boolean;
+        resolveJsonModule?: boolean;
         types?: string[];
         /** Paths used to used to compute primary types search locations */
         typeRoots?: string[];

tests/baselines/reference/api/typescript.d.ts

@@ -2390,6 +2390,7 @@ declare namespace ts {
         suppressImplicitAnyIndexErrors?: boolean;
         target?: ScriptTarget;
         traceResolution?: boolean;
+        resolveJsonModule?: boolean;
         types?: string[];
         /** Paths used to compute primary types search locations */
         typeRoots?: string[];