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Suppress PowerShell progress bars before Invoke-WebRequest (or its alias iwr) by setting $ProgressPreference = 'SilentlyContinue'.
PropertyValue
SeverityStyle
CategoryStyle
DefaultEnabled
Auto-fixYes (--fix --fix-unsafe)

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Description

PowerShell’s Invoke-WebRequest renders a per-response progress bar by default. On Windows containers this collapses download throughput by an order of magnitude because the host cannot render the bar and the cmdlet stalls waiting for terminal updates. Microsoft’s official Windows container guidance is to set $ProgressPreference = 'SilentlyContinue' before any Invoke-WebRequest call. The rule fires whenever a RUN invokes Invoke-WebRequest or iwr without a preceding $ProgressPreference = 'SilentlyContinue' assignment. Detection does not depend on the stage’s default shell — Invoke-WebRequest is a PowerShell-unique cmdlet, so finding it is itself the shell signal. That way the rule catches both SHELL-based PowerShell stages and one-off powershell -Command wrappers embedded inside bash stages.

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Why this matters

On Windows Server Core images specifically, users have reported Invoke-WebRequest downloads taking minutes where a curl or the same call with $ProgressPreference = 'SilentlyContinue' takes seconds. The progress bar is pure noise in a non-interactive build step.

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Examples

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Before (violation)

FROM mcr.microsoft.com/powershell:ubuntu-22.04
SHELL ["pwsh", "-Command"]
RUN Invoke-WebRequest https://example.com/file.zip -OutFile /tmp/file.zip

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After (fixed with --fix --fix-unsafe)

FROM mcr.microsoft.com/powershell:ubuntu-22.04
SHELL ["pwsh", "-Command", "$ProgressPreference = 'SilentlyContinue';"]
RUN Invoke-WebRequest https://example.com/file.zip -OutFile /tmp/file.zip

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Already clean (no violation)

FROM mcr.microsoft.com/powershell:ubuntu-22.04
SHELL ["pwsh", "-Command", "$ErrorActionPreference = 'Stop'; $PSNativeCommandUseErrorActionPreference = $true; $ProgressPreference = 'SilentlyContinue';"]
RUN Invoke-WebRequest https://example.com/file.zip -OutFile /tmp/file.zip

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Explicit wrapper (violation)

FROM ubuntu:22.04
RUN pwsh -Command "Invoke-WebRequest https://example.com/file.zip -OutFile /tmp/file.zip"
The fix prepends the assignment to the inner script: 
FROM ubuntu:22.04
RUN pwsh -Command "$ProgressPreference = 'SilentlyContinue'; Invoke-WebRequest https://example.com/file.zip -OutFile /tmp/file.zip"

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Fix behavior

The fix adapts to where the PowerShell script lives:
  • SHELL with bare -Command: appends a new array element "$ProgressPreference = 'SilentlyContinue';" to the SHELL instruction.
  • SHELL with an existing prelude: appends the assignment to the existing prelude string, inserting a ; separator if missing.
  • No SHELL in a PowerShell-by-default stage: inserts a new SHELL instruction after the FROM.
  • Explicit powershell -Command / pwsh -Command wrapper: zero-width insertion at the start of the inner script.
  • RUN <<EOF heredoc body (PowerShell stages only): inserts the assignment on a new line at the start of the heredoc body.
The fix uses FixSuggestion safety — it requires --fix-unsafe to apply. A same-SHELL-scope suppression prevents duplicate SHELL edits when multiple RUNs in the same stage violate.

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Interaction with other rules

  • tally/powershell/prefer-shell-instruction (priority 95): when it converts repeated powershell -Command wrappers to a SHELL instruction, its prelude already contains $ProgressPreference = 'SilentlyContinue'. The combined --fix --fix-unsafe run lets prefer-shell-instruction win; progress-preference’s edit is dropped as overlapping.
  • tally/powershell/error-action-preference (priority 96): both rules edit the SHELL instruction with zero-width insertions before the closing ]. When both are enabled and both trigger, both apply — the resulting SHELL carries two complementary array elements, each with its own preamble.
  • tally/prefer-run-heredoc (priority 100): structural conversion to heredoc runs after the preference is set and carries it into the heredoc body.

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References

  • $ProgressPreference — Microsoft Learn: controls how PowerShell renders progress reports. Default is Continue; SilentlyContinue suppresses the per-response bar.
  • Invoke-WebRequest — Microsoft Learn: cmdlet reference documenting the progress-rendering behavior.
  • Optimize Windows Dockerfiles — Microsoft Learn: Windows-container-specific Dockerfile guidance, including the $ProgressPreference recommendation.