Mill not generating sourcemaps when using scalajs >= 1.

gistfile1.txt

❯ ./mill scalajslib.test 'mill.scalajslib.HelloJSWorldTests.fastOpt'
[94/356] scalajslib.worker[1].compile
[info] Compiling 1 Scala source to /h/mill/out/scalajslib/worker/1/compile/dest/classes ...
[warn] 1 deprecation (since 2.13.0); re-run with -deprecation for details
[warn] one warning found
[info] Done compiling.
[221/356] main.core.compile
[info] Compiling 1 Scala source to /h/mill/out/main/core/compile/dest/classes ...
[info] Done compiling.
[356/356] scalajslib.test.test
----------- Running Tests mill.scalajslib.HelloJSWorldTests.fastOpt -----------
mill.scalajslib.HelloJSWorldTests: Using experimental parallel evaluator with 4 threads
mill.scalajslib.HelloJSWorldTests: [#2] [39/44] helloJsWorld[2.13.2,1.1.0].toolsClasspath
[#3] [info] Compiling 2 Scala sources to /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.13.2/1.1.0/compile/dest/classes ...
[#3] [info] Done compiling.
mill.scalajslib.HelloJSWorldTests: [#0] [43/44] helloJsWorld[2.13.2,1.1.0].fastOpt
[#0] (Config.sourceMap,true)
[#0] Linker: Compute reachability: 2055444 us
[#0] Linker: Assemble LinkedClasses: 400520 us
[#0] Linker: Check IR: 982711 us
[#0] Linker: 3877940 us
[#0] Emitter: Generate classes: 891168 us
[#0] Emitter: Write trees: 457666 us
[#0] Emitter: Class tree cache stats: reused: 486 -- invalidated: 494
[#0] Emitter: Method tree cache stats: reused: 0 -- invalidated: 3111
[#0] Emitter: 1467423 us
[#0] BasicBackend: Write result: 381683 us
mill.scalajslib.HelloJSWorldTests: Using experimental parallel evaluator with 4 threads
mill.scalajslib.HelloJSWorldTests: [#0] [38/44] helloJsWorld[2.13.2,1.0.0].compile
[#0] [info] Compiling 2 Scala sources to /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.13.2/1.0.0/compile/dest/classes ...
mill.scalajslib.HelloJSWorldTests: [#3] [39/44] helloJsWorld[2.13.2,1.0.0].toolsClasspath
[#0] [info] Done compiling.
mill.scalajslib.HelloJSWorldTests: [#2] [43/44] helloJsWorld[2.13.2,1.0.0].fastOpt
[#2] (Config.sourceMap,true)
[#2] Linker: Compute reachability: 541297 us
[#2] Linker: Assemble LinkedClasses: 79658 us
[#2] Linker: Check IR: 402236 us
[#2] Linker: 1114727 us
[#2] Emitter: Generate classes: 678850 us
[#2] Emitter: Write trees: 152211 us
[#2] Emitter: Class tree cache stats: reused: 474 -- invalidated: 482
[#2] Emitter: Method tree cache stats: reused: 0 -- invalidated: 2929
[#2] Emitter: 890019 us
mill.scalajslib.HelloJSWorldTests: Using experimental parallel evaluator with 4 threads
mill.scalajslib.HelloJSWorldTests: [#2] [38/44] helloJsWorld[2.13.2,0.6.33].compile
[#2] [info] Compiling 2 Scala sources to /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.13.2/0.6.33/compile/dest/classes ...
mill.scalajslib.HelloJSWorldTests: [#0] [39/44] helloJsWorld[2.13.2,0.6.33].toolsClasspath
[#2] [info] Done compiling.
mill.scalajslib.HelloJSWorldTests: [#0] [43/44] helloJsWorld[2.13.2,0.6.33].fastOpt
[#0] Linker: Compute reachability: 327007 us
[#0] Linker: Assemble LinkedClasses: 421580 us
[#0] Basic Linking: 991034 us
[#0] Emitter: Class tree cache stats: reused: 471 -- invalidated: 481
[#0] Emitter: Method tree cache stats: resued: 0 -- invalidated: 3190
[#0] Emitter (write output): 960549 us
mill.scalajslib.HelloJSWorldTests: Using experimental parallel evaluator with 4 threads
mill.scalajslib.HelloJSWorldTests: [#1] [39/44] helloJsWorld[2.12.11,1.1.0].toolsClasspath
[#2] [info] Compiling 2 Scala sources to /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.12.11/1.1.0/compile/dest/classes ...
[#2] [info] Done compiling.
mill.scalajslib.HelloJSWorldTests: [#1] [43/44] helloJsWorld[2.12.11,1.1.0].fastOpt
[#1] (Config.sourceMap,true)
[#0] Linker: Compute reachability: 675634 us
[#0] Linker: Assemble LinkedClasses: 41524 us
[#0] Linker: Check IR: 326203 us
[#0] Linker: 1165827 us
[#0] Emitter: Generate classes: 461910 us
[#0] Emitter: Write trees: 45529 us
[#0] Emitter: Class tree cache stats: reused: 369 -- invalidated: 372
[#0] Emitter: Method tree cache stats: reused: 0 -- invalidated: 1219
[#0] Emitter: 568344 us
[#0] BasicBackend: Write result: 201030 us
mill.scalajslib.HelloJSWorldTests: Using experimental parallel evaluator with 4 threads
mill.scalajslib.HelloJSWorldTests: [#1] [39/44] helloJsWorld[2.12.11,1.0.0].toolsClasspath
[#3] [info] Compiling 2 Scala sources to /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.12.11/1.0.0/compile/dest/classes ...
[#3] [info] Done compiling.
mill.scalajslib.HelloJSWorldTests: [#2] [43/44] helloJsWorld[2.12.11,1.0.0].fastOpt
[#2] (Config.sourceMap,true)
[#0] Linker: Compute reachability: 425060 us
[#0] Linker: Assemble LinkedClasses: 58552 us
[#0] Linker: Check IR: 314331 us
[#0] Linker: 864839 us
[#0] Emitter: Generate classes: 425146 us
[#0] Emitter: Write trees: 138065 us
[#0] Emitter: Class tree cache stats: reused: 367 -- invalidated: 370
[#0] Emitter: Method tree cache stats: reused: 0 -- invalidated: 1193
[#0] Emitter: 606005 us
mill.scalajslib.HelloJSWorldTests: Using experimental parallel evaluator with 4 threads
mill.scalajslib.HelloJSWorldTests: [#1] [38/44] helloJsWorld[2.12.11,0.6.33].compile
[#1] [info] Compiling 2 Scala sources to /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.12.11/0.6.33/compile/dest/classes ...
mill.scalajslib.HelloJSWorldTests: [#2] [39/44] helloJsWorld[2.12.11,0.6.33].toolsClasspath
[#1] [info] Done compiling.
mill.scalajslib.HelloJSWorldTests: [#0] [43/44] helloJsWorld[2.12.11,0.6.33].fastOpt
[#0] Linker: Compute reachability: 146110 us
[#0] Linker: Assemble LinkedClasses: 475206 us
[#0] Basic Linking: 764587 us
[#0] Emitter: Class tree cache stats: reused: 334 -- invalidated: 343
[#0] Emitter: Method tree cache stats: resued: 0 -- invalidated: 1353
[#0] Emitter (write output): 675579 us
mill.scalajslib.HelloJSWorldTests: Using experimental parallel evaluator with 4 threads
mill.scalajslib.HelloJSWorldTests: [#1] [39/44] helloJsWorld[2.11.12,1.1.0].toolsClasspath
[#0] [info] Compiling 2 Scala sources to /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.11.12/1.1.0/compile/dest/classes ...
[#0] [info] Done compiling.
mill.scalajslib.HelloJSWorldTests: [#2] [43/44] helloJsWorld[2.11.12,1.1.0].fastOpt
[#2] (Config.sourceMap,true)
[#0] Linker: Compute reachability: 758258 us
[#0] Linker: Assemble LinkedClasses: 84209 us
[#0] Linker: Check IR: 798437 us
[#0] Linker: 1741239 us
[#0] Emitter: Generate classes: 968241 us
[#0] Emitter: Write trees: 82016 us
[#0] Emitter: Class tree cache stats: reused: 419 -- invalidated: 422
[#0] Emitter: Method tree cache stats: reused: 0 -- invalidated: 1121
[#0] Emitter: 1233548 us
[#0] BasicBackend: Write result: 143015 us
mill.scalajslib.HelloJSWorldTests: Using experimental parallel evaluator with 4 threads
mill.scalajslib.HelloJSWorldTests: [#3] [38/44] helloJsWorld[2.11.12,1.0.0].compile
[#3] [info] Compiling 2 Scala sources to /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.11.12/1.0.0/compile/dest/classes ...
mill.scalajslib.HelloJSWorldTests: [#1] [39/44] helloJsWorld[2.11.12,1.0.0].toolsClasspath
[#3] [info] Done compiling.
mill.scalajslib.HelloJSWorldTests: [#3] [43/44] helloJsWorld[2.11.12,1.0.0].fastOpt
[#3] (Config.sourceMap,true)
[#1] Linker: Compute reachability: 394407 us
[#1] Linker: Assemble LinkedClasses: 70362 us
[#1] Linker: Check IR: 271448 us
[#1] Linker: 832441 us
[#1] Emitter: Generate classes: 485705 us
[#1] Emitter: Write trees: 136191 us
[#1] Emitter: Class tree cache stats: reused: 421 -- invalidated: 424
[#1] Emitter: Method tree cache stats: reused: 0 -- invalidated: 1130
[#1] Emitter: 676171 us
mill.scalajslib.HelloJSWorldTests: Using experimental parallel evaluator with 4 threads
mill.scalajslib.HelloJSWorldTests: [#0] [38/44] helloJsWorld[2.11.12,0.6.33].compile
[#0] [info] Compiling 2 Scala sources to /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.11.12/0.6.33/compile/dest/classes ...
mill.scalajslib.HelloJSWorldTests: [#1] [39/44] helloJsWorld[2.11.12,0.6.33].toolsClasspath
[#0] [info] Done compiling.
mill.scalajslib.HelloJSWorldTests: [#1] [43/44] helloJsWorld[2.11.12,0.6.33].fastOpt
[#1] Linker: Compute reachability: 845645 us
[#1] Linker: Assemble LinkedClasses: 1471614 us
[#1] Basic Linking: 3106391 us
[#1] Emitter: Class tree cache stats: reused: 323 -- invalidated: 333
[#1] Emitter: Method tree cache stats: resued: 0 -- invalidated: 1143
[#1] Emitter (write output): 2073774 us
+ mill.scalajslib.HelloJSWorldTests.fastOpt 138235ms

/h/mill master* 2m 58s
❯ ls /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.13.2/0.6.33/fastOpt/dest/
out.js  out.js.map

/h/mill master*
❯ ls /h/mill/target/workspace/mill/scalajslib/HelloJSWorldTests/helloWorldEvaluator/helloJsWorld/2.13.2/1.1.0/fastOpt/dest
out.js