Function calls in conditional breakpoints not supported

[blacktop]

Running latest everything on Mac

cond bkpt: strings.EqualFold("pdf", plugin.name)

Failed to continue.

Steps to Reproduce:

{
  // Use IntelliSense to learn about possible attributes.
  // Hover to view descriptions of existing attributes.
  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Scan",
      "type": "go",
      "request": "launch",
      "mode": "debug",
      "remotePath": "",
      "port": 2345,
      "host": "127.0.0.1",
      "program": "${workspaceRoot}",
      "env": {},
      "args": [
        "scan",
        "eicar.pdf"
      ],
      "showLog": true
    }
  ]
}

[blacktop]

@ramya-rao-a

[ramya-rao-a]

Please provide a small sample code along with the location where you tried to add the conditional breakpoint.

[blacktop]

package main

import (
	"fmt"
	"strings"
)

func main() {
	list := [3]string{"1", "2", "3"}

	for _,num := range list {
		if strings.EqualFold("2", num){
			fmt.Println(num)       <=========== cond bp: `strings.EqualFold(num,"2")`
		}
	}
}

OUTPUT:

API server listening at: 127.0.0.1:11670
time="2018-07-25T21:26:10-04:00" level=info msg="launching process with args: [/Users/blacktop/go/src/github.com/blacktop/cond-bp-test/debug]" layer=debugger
time="2018-07-25T21:26:11-04:00" level=info msg="created breakpoint: &api.Breakpoint{ID:1, Name:\"\", Addr:0x10af68d, File:\"/Users/blacktop/go/src/github.com/blacktop/cond-bp-test/main.go\", Line:13, FunctionName:\"main.main\", Cond:\"strings.EqualFold(\\\"2\\\", num)\", Tracepoint:false, Goroutine:false, Stacktrace:0, Variables:[]string(nil), LoadArgs:(*api.LoadConfig)(0xc420024cc0), LoadLocals:(*api.LoadConfig)(0xc420024cf0), HitCount:map[string]uint64{}, TotalHitCount:0x0}" layer=debugger
time="2018-07-25T21:26:11-04:00" level=debug msg=continuing layer=debugger
"Failed to continue."

Breakpoint has an ! in it and when you hover on it it says: Conditional breakpoints not supported by this debug type

VSCode: 1.25.1
vscode-go: 0.6.84

[blacktop]

^ I confirmed that this toy example does work in GoLand. Just FYI

[lggomez]

There are 2 issues here:

• The extension supports conditional breakpoints, but it looks like sometimes it still gives the unsopported warning when it shouldn't. I could reproduce it but I don't have a list of steps yet
• Conditional expressions with external package references aren't working: the expression num == "2" works but fmt.Sprintf("%s",num) == "2" doesn't

I will look into the second issue first

[lggomez]

I debugged the debug adapter and found out that this is actually a limitation of delve: https://github.com/derekparker/delve/blob/2a2d1040e9b85e069c101bf9916d333e9e3cf54d/pkg/proc/eval.go#L373-L403

I don't have Goland to compare but my guess is that they're either using another debugger or a fork/built-in solution

[blacktop]

@lggomez thank you for digging into this! It is good to know it does work for the example you gave as I can use that (as I do ❤️ vscode and was sad it wasn't working). You can try Goland for free as a trial I believe? That is interesting that they are using a delve fork. Hmmm.

Anyway thanks again!

[blacktop]

Maybe vscode-go could give a different error message to let the user know they can't use functions in conditional breakpoints?

[blacktop]

Okay so my test was flawed. My greatest apologies to both of you 😞 I re-ran this func:

package main

import (
	"fmt"
)

func main() {
	list := [3]string{"1", "2", "3"}

	for _, num := range list {
		// if strings.EqualFold("2", num){
		fmt.Println(num) <=============== COND BP: strings.EqualFold("2", num)
		// }
	}
}

And it stopped in GoLand.... ON num=="1" !?!?! 😡

So cond breakpoints just "fail open" on GoLand where they "fail closed" on vscode.

Universe makes sense again and vscode is once again the one true editor!!! 🙏

[blacktop]

I might be cool if vscode would say:

Hey, this cond bp isn't supported so we are going to turn it back into a regular bp. Cool?

[lggomez]

@blacktop I sent a PR to make the logs more clear: #1815

Goland is a completely different beast: IntelliJ (the core IDE) has its AST engine, so they have implemented their own Go lexer/parser in order to make the most of it, and that's how the IDE refactorings look so seamless and assorted in comparison

I bet they use delve as the debug backend, and they may attempt to extract the function calls to a shadow variable in order to support this scenario. I'm just speculating though, their current implementation is closed source

[ramya-rao-a]

This is some great investigation going on here :) Thanks @lggomez and @blacktop
I've merged the PR from @lggomez that adds the errors from delve into the logs.
Closing this issue as there isnt much we can do here