@@ -878,12 +878,13 @@ namespace ts {
878878 type ResolutionKindSpecificLoader = ( extensions : Extensions , candidate : string , onlyRecordFailures : boolean , state : ModuleResolutionState ) => Resolved | undefined ;
879879
880880 /**
881- * Any module resolution kind can be augmented with optional settings: 'baseUrl', 'paths' and 'rootDirs' - they are used to
881+ * Any module resolution kind can be augmented with optional settings: 'baseUrl', 'resolveFromOutDir', ' paths' and 'rootDirs' - they are used to
882882 * mitigate differences between design time structure of the project and its runtime counterpart so the same import name
883883 * can be resolved successfully by TypeScript compiler and runtime module loader.
884884 * If these settings are set then loading procedure will try to use them to resolve module name and it can of failure it will
885885 * fallback to standard resolution routine.
886886 *
887+ * 'resolveFromOutDir': TODO document the semantics
887888 * - baseUrl - this setting controls how non-relative module names are resolved. If this setting is specified then non-relative
888889 * names will be resolved relative to baseUrl: i.e. if baseUrl is '/a/b' then candidate location to resolve module name 'c/d' will
889890 * be '/a/b/c/d'
@@ -940,6 +941,9 @@ namespace ts {
940941 function tryLoadModuleUsingOptionalResolutionSettings ( extensions : Extensions , moduleName : string , containingDirectory : string , loader : ResolutionKindSpecificLoader ,
941942 state : ModuleResolutionState ) : Resolved | undefined {
942943
944+ const resolvedFromOutDir = tryLoadModuleUsingOutDirIfEligible ( extensions , moduleName , containingDirectory , loader , state ) ;
945+ if ( resolvedFromOutDir ) return resolvedFromOutDir ;
946+
943947 const resolved = tryLoadModuleUsingPathsIfEligible ( extensions , moduleName , loader , state ) ;
944948 if ( resolved ) return resolved . value ;
945949
@@ -965,6 +969,51 @@ namespace ts {
965969 }
966970 }
967971
972+ function tryLoadModuleUsingOutDirIfEligible ( extensions : Extensions , moduleName : string , containingDirectory : string , loader : ResolutionKindSpecificLoader , state : ModuleResolutionState ) : Resolved | undefined {
973+ const { baseUrl, resolveFromOutDir, outDir, rootDir } = state . compilerOptions ;
974+ if ( ! resolveFromOutDir ) {
975+ return undefined ;
976+ }
977+ if ( ! outDir ) {
978+ return undefined ;
979+ }
980+ if ( state . traceEnabled ) {
981+ trace ( state . host , Diagnostics . resolveFromOutDir_option_is_set_using_it_to_resolve_relative_module_name_0 , moduleName ) ;
982+ }
983+
984+ // COMMENT FOR REVIEWER: Is there a more robust way to determine the base directory here?
985+ var baseDirectory = baseUrl ;
986+ if ( ! baseDirectory && state . host . getCurrentDirectory ) {
987+ baseDirectory = state . host . getCurrentDirectory ( ) ;
988+ }
989+ if ( ! baseDirectory ) {
990+ return undefined ;
991+ }
992+
993+ // COMMENT FOR REVIEWER: I've seen rootDir be relative path and and absolute path so
994+ // handling both cases here to come up with an absolute normalizedPrefix path
995+ var normalizedPrefix = rootDir && ts . startsWith ( rootDir , ts . directorySeparator ) ?
996+ ts . normalizePath ( rootDir ) :
997+ ts . normalizePath ( ts . combinePaths ( baseDirectory , rootDir ) ) ;
998+ var candidate = ts . normalizePath ( ts . combinePaths ( containingDirectory , moduleName ) ) ;
999+
1000+ // COMMENT FOR REVIEWER: No ts.relativePath() function that I could find. Is there one
1001+ // somewhere that I'm not aware of?
1002+ var suffix = require ( "path" ) . relative ( normalizedPrefix , candidate ) ;
1003+ candidate = ts . normalizePath ( ts . combinePaths ( baseDirectory , outDir , suffix ) )
1004+ if ( state . traceEnabled ) {
1005+ trace ( state . host , Diagnostics . Loading_0_from_the_out_dir_1_candidate_location_2 , suffix , outDir , candidate ) ;
1006+ }
1007+ const resolvedFileName = loader ( extensions , candidate , ! directoryProbablyExists ( containingDirectory , state . host ) , state ) ;
1008+ if ( resolvedFileName ) {
1009+ return resolvedFileName ;
1010+ }
1011+ if ( state . traceEnabled ) {
1012+ trace ( state . host , Diagnostics . Module_resolution_using_outDir_has_failed ) ;
1013+ }
1014+ return undefined ;
1015+ }
1016+
9681017 function tryLoadModuleUsingRootDirs ( extensions : Extensions , moduleName : string , containingDirectory : string , loader : ResolutionKindSpecificLoader ,
9691018 state : ModuleResolutionState ) : Resolved | undefined {
9701019
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