Allow --incremental to be command line option

src/compiler/commandLineParser.ts

@@ -136,6 +136,13 @@ namespace ts {
             category: Diagnostics.Advanced_Options,
             description: Diagnostics.Show_verbose_diagnostic_information
         },
+        {
+            name: "incremental",
+            shortName: "i",
+            type: "boolean",
+            category: Diagnostics.Basic_Options,
+            description: Diagnostics.Enable_incremental_compilation,
+        },
     ];
 
     /* @internal */
@@ -331,13 +338,6 @@ namespace ts {
             category: Diagnostics.Basic_Options,
             description: Diagnostics.Enable_project_compilation,
         },
-        {
-            name: "incremental",
-            type: "boolean",
-            isTSConfigOnly: true,
-            category: Diagnostics.Basic_Options,
-            description: Diagnostics.Enable_incremental_compilation,
-        },
         {
             name: "tsBuildInfoFile",
             type: "string",

src/compiler/diagnosticMessages.json

@@ -3072,6 +3072,10 @@
         "category": "Error",
         "code": 5073
     },
+    "Option '--incremental' can only be speicified when using tsconfig.": {
+        "category": "Error",
+        "code": 5074
+    },
 
     "Generates a sourcemap for each corresponding '.d.ts' file.": {
         "category": "Message",

src/compiler/program.ts

@@ -2722,6 +2722,10 @@ namespace ts {
                 createDiagnosticForOptionName(Diagnostics.Option_paths_cannot_be_used_without_specifying_baseUrl_option, "paths");
             }
 
+            if (options.incremental && !options.configFilePath) {
+                programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Option_incremental_can_only_be_speicified_when_using_tsconfig));
+            }
+
             if (options.composite) {
                 if (options.declaration === false) {
                     createDiagnosticForOptionName(Diagnostics.Composite_projects_may_not_disable_declaration_emit, "declaration");

src/compiler/tsbuild.ts

@@ -30,6 +30,7 @@ namespace ts {
         listEmittedFiles?: boolean;
         listFiles?: boolean;
         pretty?: boolean;
+        incremental?: boolean;
 
         traceResolution?: boolean;
         /* @internal */ diagnostics?: boolean;
@@ -363,7 +364,7 @@ namespace ts {
     function getCompilerOptionsOfBuildOptions(buildOptions: BuildOptions): CompilerOptions {
         const result = {} as CompilerOptions;
         commonOptionsWithBuild.forEach(option => {
-            result[option.name] = buildOptions[option.name];
+            if (hasProperty(buildOptions, option.name)) result[option.name] = buildOptions[option.name];
         });
         return result;
     }

src/testRunner/unittests/config/commandLineParsing.ts

@@ -370,16 +370,9 @@ namespace ts {
             // --lib es6 0.ts
             assertParseResult(["--incremental", "0.ts"],
                 {
-                    errors: [{
-                        messageText: "Option 'incremental' can only be specified in 'tsconfig.json' file.",
-                        category: Diagnostics.Option_0_can_only_be_specified_in_tsconfig_json_file.category,
-                        code: Diagnostics.Option_0_can_only_be_specified_in_tsconfig_json_file.code,
-                        file: undefined,
-                        start: undefined,
-                        length: undefined,
-                    }],
+                    errors: [],
                     fileNames: ["0.ts"],
-                    options: {}
+                    options: { incremental: true }
                 });
         });
     });
@@ -477,16 +470,9 @@ namespace ts {
             // --lib es6 0.ts
             assertParseResult(["--incremental", "tests"],
                 {
-                    errors: [{
-                        messageText: "Unknown build option '--incremental'.",
-                        category: Diagnostics.Unknown_build_option_0.category,
-                        code: Diagnostics.Unknown_build_option_0.code,
-                        file: undefined,
-                        start: undefined,
-                        length: undefined,
-                    }],
+                    errors: [],
                     projects: ["tests"],
-                    buildOptions: { }
+                    buildOptions: { incremental: true }
                 });
         });