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Minify the shadowed JAR with R8 - #669

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Goooler:shadow-with-r8
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Minify the shadowed JAR with R8#669
Goooler wants to merge 1 commit into
Kotlin:mainfrom
Goooler:shadow-with-r8

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@Goooler

@Goooler Goooler commented Aug 12, 2026

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OLD: old.jar
NEW: new.jar

       │              compressed               │             uncompressed
       ├────────────┬────────────┬─────────────┼────────────┬───────────┬─────────────
 JAR   │ old        │ new        │ diff        │ old        │ new       │ diff
───────┼────────────┼────────────┼─────────────┼────────────┼───────────┼─────────────
 class │  66.07 MiB │  14.71 MiB │  -51.36 MiB │ 167.93 MiB │ 29.43 MiB │  -138.5 MiB
 other │ 996.67 KiB │ 829.11 KiB │ -167.56 KiB │   2.03 MiB │  1.94 MiB │  -86.02 KiB
───────┼────────────┼────────────┼─────────────┼────────────┼───────────┼─────────────
 total │  67.04 MiB │  15.52 MiB │  -51.52 MiB │ 169.96 MiB │ 31.37 MiB │ -138.59 MiB

 CLASSES │ old    │ new   │ diff
─────────┼────────┼───────┼────────────────────────
 classes │  32906 │ 10526 │  -22380 (+1 -22381)
 methods │ 309307 │ 74531 │ -234776 (+268 -235044)
  fields │  78688 │ 23174 │  -55514 (+12 -55526)

@Goooler

Goooler commented Aug 12, 2026

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Just a quick note: we don't need to merge this for now. The main purpose here is to show the difference between the before and after.

#584 has been merged for minification and to provide a binary JAR. It should be a better replacement for this version.

@Goooler

Goooler commented Aug 12, 2026

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BTW, I fed the output of the shadowed JAR into the native image input and the final binary size was reduced slightly.

bloaty -d symbols ktfmt-native-old -- ktfmt-native-new

    FILE SIZE        VM SIZE
 --------------  --------------
  +8.5% +2.12Mi  +8.5% +2.12Mi    [__DATA,__svm_heap]
  +6.1%  +193Ki  +6.1%  +193Ki    ___svm_code_section
  +2.4% +11.9Ki  +3.2% +16.0Ki    [__LINKEDIT]
  +428% +1.34Ki  +428% +1.34Ki    [__DATA,__data]
  +4.4%    +720  +4.4%    +720    [__TEXT]
  +2.5%     +96  +2.5%     +96    _sbom
  -0.4%     -96  -0.2%     -96    [__DATA]
 -44.3% -1.34Ki -44.3% -1.34Ki    _sbom_length
  -5.1% -1.03Mi  -5.1% -1.03Mi    _IsolateEnterStub__JavaMainWrapper__run__cXbfAhOWcF90761nQYco7L
  +2.6% +1.29Mi  +2.7% +1.30Mi    TOTAL

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@hick209

hick209 commented Aug 14, 2026

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This is really nice improvement, thanks for submitting the PR.

I noticed you did not update the CHANGELOG.md, would you mind doing that?

@Goooler

Goooler commented Aug 14, 2026

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I sent this to demonstrate a potential use case, but I don't have a strong opinion on whether it should be merged. Because there are so many cases that can't be covered by the current tests. I would prefer closing this or holding it.

@ZacSweers

ZacSweers commented Aug 16, 2026 •
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I think its worthwhile to do (I contributed this feature to shadow!) and it's doable to make a custom Test task that tests with this minified jar. I do think it shouldn't be obfuscated though, as that'll make bugs nigh-impossible to report for users. I don't know how this would interact with native image though, it may require a bit more work

Goooler
Goooler commented Aug 17, 2026
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Comment thread build.gradle.kts Outdated

dependencies { add(ktfmtCliDependencies.name, project(":ktfmt")) }
dependencies {
ktfmtCliDependencies(project(path = ":ktfmt", configuration = "shadow"))

@Goooler Goooler Aug 17, 2026

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This is too annoying for developments. Reverted.

Comment thread core/build.gradle.kts Outdated
Comment on lines +106 to +119
// Run unit tests against the R8-processed shadow JAR to ensure Maven API compatibility
val testShadow =
register("testShadow", Test::class) {
group = "verification"
description = "Runs unit tests against the R8-processed shadow JAR."
dependsOn(shadowJar)
classpath =
(sourceSets["test"].runtimeClasspath - sourceSets["main"].output) +
files(shadowJar.flatMap { it.archiveFile })
testClassesDirs = sourceSets["test"].output.classesDirs
}

check {
dependsOn(testShadow)

@Goooler Goooler Aug 17, 2026 •
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This should cover the test cases in current behaviors. Refined a bit.

Comment thread buildSrc/src/main/kotlin/org/jetbrains/ktfmt/NativeImagePlugin.kt Outdated
Comment on lines +165 to +168
classpath.setFrom(
nativeImageJar.flatMap { it.archiveFile },
project.tasks.named("shadowJar", Jar::class).flatMap { it.archiveFile },
project.configurations.getByName("nativeImageClasspath"),

@Goooler Goooler Aug 17, 2026 •
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We have no much necessary to feed the shadowJar to the native image building. Reverted.

@Goooler

Goooler commented Aug 17, 2026

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OLD: old.jar
NEW: new.jar

       │              compressed              │             uncompressed             
       ├────────────┬───────────┬─────────────┼────────────┬───────────┬─────────────
 JAR   │ old        │ new       │ diff        │ old        │ new       │ diff        
───────┼────────────┼───────────┼─────────────┼────────────┼───────────┼─────────────
 class │  66.09 MiB │ 14.12 MiB │  -51.97 MiB │    168 MiB │    28 MiB │ -140.01 MiB 
 other │ 997.03 KiB │ 826.3 KiB │ -170.72 KiB │   2.03 MiB │  1.94 MiB │  -87.19 KiB 
───────┼────────────┼───────────┼─────────────┼────────────┼───────────┼─────────────
 total │  67.07 MiB │ 14.93 MiB │  -52.14 MiB │ 170.03 MiB │ 29.94 MiB │ -140.09 MiB 

 CLASSES │ old    │ new   │ diff                  
─────────┼────────┼───────┼───────────────────────
 classes │  32913 │ 10230 │  -22683 (+1 -22684)   
 methods │ 309579 │ 70944 │ -238635 (+72 -238707) 
  fields │  78687 │ 22714 │  -55973 (+12 -55985)

@Goooler
Minify the shadowed JAR with R8
411a290 
```
OLD: old.jar
NEW: new.jar

       │              compressed              │             uncompressed
       ├────────────┬───────────┬─────────────┼────────────┬───────────┬─────────────
 JAR   │ old        │ new       │ diff        │ old        │ new       │ diff
───────┼────────────┼───────────┼─────────────┼────────────┼───────────┼─────────────
 class │  66.09 MiB │ 14.12 MiB │  -51.97 MiB │    168 MiB │    28 MiB │ -140.01 MiB
 other │ 997.03 KiB │ 826.3 KiB │ -170.72 KiB │   2.03 MiB │  1.94 MiB │  -87.19 KiB
───────┼────────────┼───────────┼─────────────┼────────────┼───────────┼─────────────
 total │  67.07 MiB │ 14.93 MiB │  -52.14 MiB │ 170.03 MiB │ 29.94 MiB │ -140.09 MiB

 CLASSES │ old    │ new   │ diff
─────────┼────────┼───────┼───────────────────────
 classes │  32913 │ 10230 │  -22683 (+1 -22684)
 methods │ 309579 │ 70944 │ -238635 (+72 -238707)
  fields │  78687 │ 22714 │  -55973 (+12 -55985)
```
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3 participants

@Goooler @hick209 @ZacSweers