Example of Incorrect Printing

Oct 13, 2025 by wbrum.org 92 views

Introduction

When working with error messages in Julia, it's essential to ensure that they are printed correctly. However, in some cases, multiline strings can lead to incorrect printing of error messages. This article will delve into the issue of errors with multiline strings being printed incorrectly and provide a step-by-step guide to reproduce and fix the problem.

Bug Description

The issue arises when error messages are thrown from the Julia engine code and contain repeated sections. This seems to happen when the error message is a multiline string. The repeated lines are spliced into the stack trace, making it difficult to diagnose the issue.

Example of Incorrect Printing

Here's an example of how the error message is printed incorrectly:

ERROR: Julia server returned error after receiving "close" command:

Failed to close notebook: /Users/krumbiegel/.julia/dev/QuartoNotebookRunner/scratch/test.qmd

The underlying Julia error was:

Tried to close file "/Users/krumbiegel/.julia/dev/QuartoNotebookRunner/scratch/test.qmd" but the corresponding worker is busy.

Stack trace:

Failed to close notebook: /Users/krumbiegel/.julia/dev/QuartoNotebookRunner/scratch/test.qmd

The underlying Julia error was:

Tried to close file "/Users/krumbiegel/.julia/dev/QuartoNotebookRunner/scratch/test.qmd" but the corresponding worker is busy.
    at writeJuliaCommand (file:///Users/krumbiegel/dev/quarto-cli/src/execute/julia.ts:791:13)
    at eventLoopTick (ext:core/01_core.js:175:7)
    at async connectAndWriteJuliaCommandToRunningServer (file:///Users/krumbiegel/dev/quarto-cli/src/execute/julia.ts:958:20)
    at async closeWorker (file:///Users/krumbiegel/dev/quarto-cli/src/execute/julia.ts:975:3)
    at async Command.actionHandler (file:///Users/krumbiegel/dev/quarto-cli/src/execute/julia.ts:876:7)
    at async Command.execute (https://deno.land/x/cliffy@v1.0.0-rc.3/command/command.ts:1948:7)
    at async Command.parseCommand (https://deno.land/x/cliffy@v1.0.0-rc.3/command/command.ts:1780:14)
    at async quarto (file:///Users/krumbiegel/dev/quarto-cli/src/quarto.ts:191:5)
    at async file:///Users/krumbiegel/dev/quarto-cli/src/quarto.ts:220:5
    at async file:///Users/krumbiegel/dev/quarto-cli/src/core/main.ts:41:14

Steps to Reproduce

To reproduce the issue, follow these steps:

Create a Julia code that throws an error message with a multiline string.
Run the Julia code and observe the error message printed in the console.

Actual Behavior

The actual behavior is that the error message is printed incorrectly, with repeated sections spliced into the stack trace.

Expected Behavior

The expected behavior is that the error message is printed correctly, without any repeated sections.

Quarto Check Output

Here's the Quarto check output:

% quarto check
Check file:///Users/krumbiegel/dev/quarto-cli/src/quarto.ts
Quarto 99.9.9
[✓] Checking environment information...
      Quarto cache location: /Users/krumbiegel/Library/Caches/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.4.0: OK
      Dart Sass version 1.70.0: OK
      Deno version 1.46.3: OK
      Typst version 0.11.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 99.9.9
      commit: b41d51371a167411c8a6938f86d850e1e66e3108
      Path: /Users/krumbiegel/dev/quarto-cli/package/dist/bin

[✓] Checking tools....................OK
      TinyTeX: v2025.01
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /Users/krumbiegel/Library/TinyTeX/bin/universal-darwin
      Version: 2024

[✓] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
      Source: MacOS known location

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.12.2 (Conda)
      Path: /Users/krumbiegel/miniconda3/bin/python
      Jupyter: 5.5.0
      Kernels: julia-1.11, julia-1.10, julia-1.8, julia-1.7, python3

[✓] Checking Jupyter engine render....OK

[✓] Checking R installation...........OK
      Version: 4.3.2
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Users/krumbiegel/dev/quarto-cli/tests/renv/library/R-4.3/aarch64-apple-darwin20
        - /Users/krumbiegel/Library/Caches/org.R-project.R/R/renv/sandbox/R-4.3/aarch64-apple-darwin20/ac5c2659
      knitr: 1.49.8
      rmarkdown: 2.29.1

[✓] Checking Knitr engine render......OK

Fixing the Issue

To fix the issue, you need to modify the code that prints the error message. Specifically, you need to remove the repeated sections from the stack trace.

Here's an example of how you can modify the code to fix the issue:

function print_error_message(error_message)
    # Remove repeated sections from the stack trace
    stack_trace = split(error_message, "\n")
    unique_stack_trace = unique(stack_trace)
    error_message = join(unique_stack_trace, "\n")
    println(error_message)
end

By modifying the code to remove the repeated sections from the stack trace, you can ensure that the error message is printed correctly.

Conclusion

Q: What is the issue with multiline strings being printed incorrectly?

A: The issue arises when error messages are thrown from the Julia engine code and contain repeated sections. This seems to happen when the error message is a multiline string. The repeated lines are spliced into the stack trace, making it difficult to diagnose the issue.

Q: What is the expected behavior when printing error messages with multiline strings?

A: The expected behavior is that the error message is printed correctly, without any repeated sections.

Q: How can I reproduce the issue?

A: To reproduce the issue, follow these steps:

Create a Julia code that throws an error message with a multiline string.
Run the Julia code and observe the error message printed in the console.

Q: What is the Quarto check output?

A: Here's the Quarto check output:

% quarto check
Check file:///Users/krumbiegel/dev/quarto-cli/src/quarto.ts
Quarto 99.9.9
[✓] Checking environment information...
      Quarto cache location: /Users/krumbiegel/Library/Caches/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.4.0: OK
      Dart Sass version 1.70.0: OK
      Deno version 1.46.3: OK
      Typst version 0.11.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 99.9.9
      commit: b41d51371a167411c8a6938f86d850e1e66e3108
      Path: /Users/krumbiegel/dev/quarto-cli/package/dist/bin

[✓] Checking tools....................OK
      TinyTeX: v2025.01
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /Users/krumbiegel/Library/TinyTeX/bin/universal-darwin
      Version: 2024

[✓] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
      Source: MacOS known location

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.12.2 (Conda)
      Path: /Users/krumbiegel/miniconda3/bin/python
      Jupyter: 5.5.0
      Kernels: julia-1.11, julia-1.10, julia-1.8, julia-1.7, python3

[✓] Checking Jupyter engine render....OK

[✓] Checking R installation...........OK
      Version: 4.3.2
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Users/krumbiegel/dev/quarto-cli/tests/renv/library/R-4.3/aarch64-apple-darwin20
        - /Users/krumbiegel/Library/Caches/org.R-project.R/R/renv/sandbox/R-4.3/aarch64-apple-darwin20/ac5c2659
      knitr: 1.49.8
      rmarkdown: 2.29.1

[✓] Checking Knitr engine render......OK

Q: How can I fix the issue?

A: To fix the issue, you need to modify the code that prints the error message. Specifically, you need to remove the repeated sections from the stack trace.

Here's an example of how you can modify the code to fix the issue:

function print_error_message(error_message)
    # Remove repeated sections from the stack trace
    stack_trace = split(error_message, "\n")
    unique_stack_trace = unique(stack_trace)
    error_message = join(unique_stack_trace, "\n")
    println(error_message)
end

Q: What are the benefits of fixing the issue?

A: By fixing the issue, you can ensure that error messages are printed correctly, making it easier to diagnose and fix problems. This can lead to improved code quality, reduced debugging time, and increased productivity.

Q: Are there any other potential issues related to multiline strings?

A: Yes, there may be other potential issues related to multiline strings. For example, if the multiline string contains special characters or formatting, it may not be printed correctly. Additionally, if the multiline string is too long, it may exceed the maximum allowed length for a string in Julia, leading to errors.

Q: How can I prevent these issues?

A: To prevent these issues, you can follow best practices for working with multiline strings in Julia. For example, you can use string concatenation to build the multiline string, rather than trying to print it directly. You can also use string formatting to ensure that special characters and formatting are handled correctly. Additionally, you can use tools like Julia's built-in show function to print the multiline string in a more readable format.