Kotlin Language Guide¶

linthis uses ktlint for both linting and formatting, with optional detekt for additional static analysis.

Supported File Extensions¶

.kt
.kts

Required Tools¶

Linter & Formatter: ktlint¶

# macOS
brew install ktlint

# Or via curl
curl -sSLO https://github.com/pinterest/ktlint/releases/download/1.0.1/ktlint
chmod a+x ktlint

# Verify installation
ktlint --version

Optional: detekt (additional static analysis)¶

# macOS
brew install detekt

# Verify installation
detekt --version

Configuration¶

Basic Example¶

# .linthis/config.toml

[kotlin]
max_complexity = 15
excludes = ["build/**", "*.generated.kt"]

Disable Specific Rules¶

[kotlin.rules]
disable = [
    "max-line-length",
    "no-wildcard-imports"
]

Custom Rules¶

[[rules.custom]]
code = "kotlin/no-println"
pattern = "println\\s*\\("
message = "Use logging framework instead of println()"
severity = "warning"
languages = ["kotlin"]

[[rules.custom]]
code = "kotlin/no-lateinit"
pattern = "lateinit\\s+var"
message = "Consider using lazy or nullable instead of lateinit"
severity = "info"
languages = ["kotlin"]

CLI Usage¶

# Check Kotlin files only
linthis -c --lang kotlin

# Format Kotlin files only
linthis -f --lang kotlin

Ktlint Configuration¶

Create .editorconfig for ktlint:

[*.{kt,kts}]
indent_size = 4
max_line_length = 120
ktlint_code_style = ktlint_official

Or use ktlint-specific config file .ktlint:

disabled_rules=no-wildcard-imports

Detekt Configuration¶

Create detekt.yml:

complexity:
  LongMethod:
    threshold: 60
  ComplexMethod:
    threshold: 15

style:
  MaxLineLength:
    maxLineLength: 120

Common Issues¶

Ktlint not found¶

Warning: No kotlin linter available for kotlin files
  Install: brew install ktlint

Build outputs being checked¶

Add to excludes:

[kotlin]
excludes = ["build/**", "out/**", ".gradle/**"]

Generated code¶

Add generated files to excludes:

[kotlin]
excludes = ["*.generated.kt", "generated/**"]

Best Practices¶

Use .editorconfig: Standard way to configure ktlint
Android projects: Exclude generated code and build outputs
Coroutines: Be mindful of complexity in suspend functions
KDoc comments: Use KDoc for public API documentation