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Controls blank lines between Dockerfile instructions.
PropertyValue
SeverityStyle
CategoryStyle
DefaultEnabled (grouped)
Auto-fixYes (safe)

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Description

Enforces consistent blank-line spacing between Dockerfile instructions. Three modes are available:
  • grouped (default): Same instruction types are grouped together with no blank lines between them; different types are separated by exactly one blank line.
  • always: Every instruction is followed by at least one blank line.
  • never: All blank lines between instructions are removed.

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Grouped mode (default)

FROM alpine:3.20

RUN apk add --no-cache curl

ENV FOO=bar
ENV BAZ=qux

COPY . /app
Same-type instructions (both ENV) have no blank line between them. Different types (FROM to RUN, RUN to ENV, ENV to COPY) are separated by a blank line.

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Always mode

FROM alpine:3.20

RUN apk add --no-cache curl

ENV FOO=bar

ENV BAZ=qux

COPY . /app

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Never mode

FROM alpine:3.20
RUN apk add --no-cache curl
ENV FOO=bar
ENV BAZ=qux
COPY . /app

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Examples

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Bad (grouped mode, missing blank line)

FROM alpine:3.20
RUN echo hello

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Good (grouped mode)

FROM alpine:3.20

RUN echo hello

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Bad (grouped mode, unwanted blank between same types)

ENV FOO=bar

ENV BAZ=qux

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Good (grouped mode, same types adjacent)

ENV FOO=bar
ENV BAZ=qux

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Configuration

Default (grouped mode, no config needed): 
# Grouped mode is the default when the rule is enabled
Always mode: 
[rules.tally.newline-between-instructions]
mode = "always"
Never mode: 
[rules.tally.newline-between-instructions]
mode = "never"
String shorthand: 
[rules.tally]
newline-between-instructions = "always"

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Auto-fix

This rule provides safe auto-fixes:
  • Insert blank line: Adds a single blank line between instructions that need separation.
  • Remove blank lines: Removes excess blank lines between instructions that should be adjacent.
tally lint --fix Dockerfile

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Interaction with buildkit/InvalidDefinitionDescription

When both rules are enabled, buildkit/InvalidDefinitionDescription may insert blank lines between comments and instructions (to indicate a comment is not a description). These blank lines are not affected by newline-between-instructions because the newline rule only measures gaps between instruction nodes, not between comments and their associated instructions. For example, with never mode and InvalidDefinitionDescription enabled: 
# This comment doesn't describe the ARG
ARG foo=bar
FROM scratch AS base
RUN echo hello
After auto-fix, InvalidDefinitionDescription inserts a blank line between the comment and ARG, while newline-between-instructions keeps instructions adjacent: 
# This comment doesn't describe the ARG

ARG foo=bar
FROM scratch AS base
RUN echo hello