Add `:javap` and `:asmp` to the REPL #12210

griggt · 2021-04-24T22:05:59Z

I believe this draft to be fully functional, please give it a try if interested.

Unlike the Scala 2 implementation, this one has accomodations for working with JDK 16+. However, in light of the comments in scala/bug#12378, perhaps we should be looking to support an :asmp instead?

Closes lampepfl/dotty-feature-requests#80

[test_windows_full]
[test_java8]
[test_java11]
[test_java15]
[test_java17]
[test_java18]
[test_java19]

som-snytt · 2021-04-25T04:57:45Z

Can't have too many ~~toys~~ tools, but it's also true LOC are not free. OTOH existing tool works better than the not yet existing.

griggt · 2021-06-24T06:12:50Z

Now with experimental :asmp support.

dwijnand · 2021-07-29T15:46:35Z

@griggt is this still in draft or is it ready for review?

project/Build.scala

SethTisue · 2021-10-14T16:50:22Z

@griggt where does this stand? I'm interested in seeing this land and might be interested in helping. (or reviewing it, if you finish it yourself.)

griggt · 2022-03-19T02:29:26Z

It seems that our current version of scala-asm does not support Java 18 class files, so :asmp fails to disassemble them:

https://github.com/lampepfl/dotty/runs/5608623717?check_suite_focus=true#step:10:122

Error:  Test dotty.tools.repl.AsmpTests.java.lang.String signatures failed: java.lang.AssertionError: assertion failed: 
disassembly did not contain `public static varargs format(Ljava/lang/String;[Ljava/lang/Object;)Ljava/lang/String;`
Error:  Disassembly was:
Error:  Unsupported class file major version 62

By contrast the :javap implementation appears to be OK on Java 18.

--

Edit: we're on ASM 9.1, scala/scala is on 9.2
Upgrade PR: #14711

som-snytt · 2022-03-19T03:07:18Z

I've needed this so badly recently, I meant to come back and whatever the phrase is, put my shoulder to the whatever you put your shoulder to. I need to see what stuff compiles to.

Edit: I already forgot I made this comment two days ago. Actually, what I needed today is -Ygen-asmp, which I learned about recently on Scala 2.

SethTisue · 2022-03-22T18:04:43Z

We discussed this some at the Scala 3 issue spree today. One of the remaining issues is the interaction with @targetName, but I don't consider that a blocker (in part because it isn't an easy fix).

griggt · 2022-03-22T18:23:47Z

compiler/src/dotty/tools/repl/ReplDriver.scala

+    // borrowed from ExtractDependencies#recordDependency and adapted to handle @targetName
+    private def binaryClassName: String =


To expand on Seth's comment, I believe this PR correctly deals with classes with the @targetName annotation because I borrowed and adapted this binaryClassName code from ExtractDependencies. But I suspect there may be incremental compilation issues related to @targetName, and ultimately I think this binaryClassName code should be shared rather than duplicated.

I'm going to try to find some test cases and open a separate ticket for any incremental compilation issues.

This commit only provides a framework to support bytecode disassembly from within the REPL, it does not supply any concrete implementations using any particular disassembler -- those will follow in subsequent commits. Adapted from the Scala 2 :javap implementation, which was written by Paul Phillips and Som Snytt / A. P. Marki

Provides bytecode disassembly using the `javap` tool/interface supplied by the user's JDK. Adapted from the Scala 2 implementation, which was written by Paul Phillips and Som Snytt / A. P. Marki

Provides bytecode disassembly using the ASM library bundled with the Scala compiler.

ckipp01 · 2023-05-10T08:22:49Z

It's been quite some time here, so I wanted to circle back around. Is there any plans to return to this or bring it over the finish line?

SethTisue · 2023-09-16T14:42:14Z

Is there a volunteer who would like to take this over and try to get it across the finish line?

jxnu-liguobin · 2023-09-16T15:06:20Z

I have been following it for a long time when I was still using Scala2, but I don't know why it didn't move forward.

som-snytt · 2023-09-16T16:08:12Z

PSA there is no finish line. It is an oval track of endless laps.

Edit: I think there is also a PR to move repl to a subproject.

The comments made me revisit this and the scala 2 PRs. I wonder why it invites so many LOC. The scala 2 effort got pushback from retronym on complexity, and he was partially appeased. He comments sagely that it would be nice to support multi-release jars, which would hide some multiplexing/multicomplexity at the expense of a (one-time) hit to build complexity.

Alternatively, support only javap tool interface (latest) and asm is whatever the asm jar version is.

griggt force-pushed the add-javap-to-repl branch 3 times, most recently from d9e689d to 4c57f07 Compare April 25, 2021 03:46

griggt self-assigned this Apr 26, 2021

griggt force-pushed the add-javap-to-repl branch from 4c57f07 to e0a0341 Compare June 24, 2021 06:12

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griggt force-pushed the add-javap-to-repl branch 2 times, most recently from 914fe48 to ea1ce6d Compare October 3, 2021 01:26

SethTisue changed the title ~~Add :javap to the REPL~~ Add :javap and :asmp to the REPL Oct 14, 2021

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griggt force-pushed the add-javap-to-repl branch 3 times, most recently from 3ccaacb to a2c3874 Compare March 19, 2022 01:34

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griggt force-pushed the add-javap-to-repl branch from a2c3874 to 0b6af1d Compare April 27, 2022 19:44

griggt added 5 commits May 9, 2022 10:33

refactor class loader extensions

0573a77

Add :javap to the REPL

b39e3e8

Provides bytecode disassembly using the `javap` tool/interface supplied by the user's JDK. Adapted from the Scala 2 implementation, which was written by Paul Phillips and Som Snytt / A. P. Marki

tests for Javap filter selection

96ba466

Add :asmp to the REPL

4883a45

Provides bytecode disassembly using the ASM library bundled with the Scala compiler.

[do not merge] test on additional JDKs

fcfbe98

griggt force-pushed the add-javap-to-repl branch from 0b6af1d to fcfbe98 Compare May 9, 2022 22:01

SethTisue unassigned griggt Sep 16, 2023

nicolasstucki assigned dwijnand Feb 1, 2024

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Add `:javap` and `:asmp` to the REPL #12210

Add `:javap` and `:asmp` to the REPL #12210

griggt commented Apr 24, 2021 •

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griggt commented Mar 19, 2022 •

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som-snytt commented Sep 16, 2023 •

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		// borrowed from ExtractDependencies#recordDependency and adapted to handle @targetName
		private def binaryClassName: String =

Add :javap and :asmp to the REPL #12210

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Add :javap and :asmp to the REPL #12210

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Add `:javap` and `:asmp` to the REPL #12210

Add `:javap` and `:asmp` to the REPL #12210

griggt commented Apr 24, 2021 •

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som-snytt commented Mar 19, 2022 •

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