feat: Add scalafix linter support

.gitattributes

@@ -8,3 +8,8 @@ examples export-ignore
 
 # Substitution for the _VERSION_PRIVATE placeholder
 tools/version.bzl export-subst
+
+#################################
+# Generated files - collapse in GitHub diffs and hide from git diff
+#################################
+**/maven_install.json linguist-generated=true -diff

MODULE.bazel

@@ -30,6 +30,7 @@ bazel_dep(name = "rules_multitool", version = "0.11.0")
 bazel_dep(name = "rules_diff", version = "1.0.0")
 bazel_dep(name = "rules_shell", version = "0.5.0")
 bazel_dep(name = "rules_java", version = "7.0.6")
+bazel_dep(name = "rules_scala", version = "7.1.6")
 
 # Needed in the root because we use the run_clippy action in our aspect impl
 bazel_dep(name = "rules_rust", version = "0.67.0")

README.md

@@ -52,7 +52,7 @@ Linters which are not language-specific:
 | Ruby                   |                           | [RuboCop], [Standard]                      |
 | Rust                   | [rustfmt]                 | [clippy]                                   |
 | SQL                    | [prettier-plugin-sql]     |                                            |
-| Scala                  | [scalafmt]                |                                            |
+| Scala                  | [scalafmt]                | [scalafix]                                 |
 | Shell                  | [shfmt]                   | [shellcheck]                               |
 | Starlark               | [Buildifier]              |                                            |
 | Swift                  | [SwiftFormat] (1)         |                                            |
@@ -86,6 +86,7 @@ Linters which are not language-specific:
 [gofumpt]: https://github.com/mvdan/gofumpt
 [jsonnetfmt]: https://github.com/google/go-jsonnet
 [scalafmt]: https://scalameta.org/scalafmt
+[scalafix]: https://scalacenter.github.io/scalafix/
 [rubocop]: https://docs.rubocop.org/
 [standard]: https://github.com/standardrb/standard
 [ruff]: https://docs.astral.sh/ruff/

examples/scala/.bazelrc

@@ -1 +1,8 @@
 import %workspace%/../java/tools/java21.bazelrc
+
+# Use syntactic mode for targets without SemanticDB
+build:lint --aspects=//tools/lint:linters.bzl%scalafix
+
+# Use semantic mode for targets with SemanticDB enabled
+# Note: semantic mode can also run syntactic rules if configured in .scalafix.semantic.conf
+build:lint-semantic --aspects=//tools/lint:linters.bzl%scalafix_semantic

examples/scala/.scalafix.conf

@@ -0,0 +1,27 @@
+# Scalafix configuration
+# See https://scalacenter.github.io/scalafix/docs/users/configuration.html
+
+rules = [
+  DisableSyntax
+  LeakingImplicitClassVal
+  NoValInForComprehension
+  ProcedureSyntax
+]
+
+# DisableSyntax configuration
+DisableSyntax.noVars = true
+DisableSyntax.noNulls = true
+DisableSyntax.noReturns = true
+DisableSyntax.noWhileLoops = true
+DisableSyntax.noAsInstanceOf = true
+DisableSyntax.noIsInstanceOf = true
+
+# OrganizeImports configuration (requires semantic mode)
+# To enable semantic rules, you need to:
+# 1. Configure your scala_toolchain with enable_semanticdb = True
+# 2. Use lint_scalafix_aspect with semantic = True
+# 3. Uncomment the OrganizeImports rule above
+#
+# OrganizeImports.removeUnused = true
+# OrganizeImports.groupedImports = Merge
+# OrganizeImports.importsOrder = Ascii

examples/scala/.scalafix.semantic.conf

@@ -0,0 +1,28 @@
+rules = [
+  # Syntactic rules (also work without SemanticDB)
+  DisableSyntax
+  LeakingImplicitClassVal
+  NoValInForComprehension
+  ProcedureSyntax
+
+  # Semantic rules (require SemanticDB)
+  OrganizeImports
+]
+
+# DisableSyntax configuration
+DisableSyntax.noVars = true
+DisableSyntax.noNulls = true
+DisableSyntax.noReturns = true
+DisableSyntax.noWhileLoops = true
+DisableSyntax.noAsInstanceOf = true
+DisableSyntax.noIsInstanceOf = true
+
+# OrganizeImports configuration
+# Note: removeUnused requires -Wunused:imports compiler flag
+OrganizeImports.removeUnused = false
+OrganizeImports.groupedImports = Merge
+OrganizeImports.groups = [
+  "re:javax?\\.",
+  "scala.",
+  "*"
+]

examples/scala/BUILD

@@ -2,5 +2,7 @@ package(default_visibility = ["//visibility:public"])
 
 exports_files([
     ".scalafmt.conf",
+    ".scalafix.conf",
+    ".scalafix.semantic.conf",
     "maven_install.json",
 ])

examples/scala/MODULE.aspect

@@ -0,0 +1,8 @@
+# Aspect Extension setup for CLI "lint" and "format" commands
+# This example is in rules_lint, so we use a local dependency.
+# See https://github.com/bazel-starters/scala for a real-world example.
+axl_local_dep(
+    name = "rules_lint",
+    path = "../..",
+    auto_use_tasks = True,
+)

examples/scala/MODULE.bazel

@@ -1,19 +1,37 @@
-"Bazel dependencies for Scala formatting example"
+"Bazel dependencies for Scala formatting and linting example"
 
 bazel_dep(name = "aspect_rules_lint")
 bazel_dep(name = "rules_jvm_external", version = "6.5")
 bazel_dep(name = "rules_java", version = "8.5.0")
+bazel_dep(name = "rules_scala", version = "7.1.6")
 bazel_dep(name = "bazel_skylib", version = "1.4.2")
 
 local_path_override(
     module_name = "aspect_rules_lint",
     path = "../..",
 )
 
+# Configure Scala version - must match rules_scala's expected version
+scala_config = use_extension(
+    "@rules_scala//scala/extensions:config.bzl",
+    "scala_config",
+)
+scala_config.settings(scala_version = "2.13.17")
+
+# Load Scala dependency toolchains
+scala_deps = use_extension(
+    "@rules_scala//scala/extensions:deps.bzl",
+    "scala_deps",
+)
+scala_deps.scala()
+
 maven = use_extension("@rules_jvm_external//:extensions.bzl", "maven")
 maven.install(
     artifacts = [
-        "org.scalameta:scalafmt-cli_2.13:3.7.14",
+        "org.scalameta:scalafmt-cli_2.13:3.9.10",
+        # scalafix-cli is published for specific Scala versions
+        # Use 2.13.18 which has version 0.14.5 available on Maven Central
+        "ch.epfl.scala:scalafix-cli_2.13.18:0.14.5",
     ],
     lock_file = "@//:maven_install.json",
     repositories = [
@@ -22,3 +40,6 @@ maven.install(
     ],
 )
 use_repo(maven, "maven")
+
+# Register custom toolchain with SemanticDB enabled for semantic linting rules
+register_toolchains("//tools/scala:semanticdb_toolchain")

examples/scala/README.md

@@ -1,26 +1,32 @@
-# Scala Formatting Example
+# Scala Formatting and Linting Example
 
-This example demonstrates how to set up formatting for Scala code using `rules_lint`.
+This example demonstrates how to set up formatting and linting for Scala code using `rules_lint`.
 
 ## Supported Tools
 
 ### Formatters
 
 - **Scalafmt** - Code formatter for Scala
 
-Note: No Scala linter is currently available in rules_lint.
+### Linters
+
+- **Scalafix** - Scala linter and refactoring tool (syntactic + semantic rules)
 
 ## Setup
 
 1. Configure MODULE.bazel with required dependencies
 2. Create the MODULE.aspect file to register CLI tasks
-3. Configure Maven Dependencies (add scalafmt to maven.install artifacts)
-4. Configure Formatters
+3. Configure Maven Dependencies (add scalafmt + scalafix to maven.install artifacts)
+4. Configure Formatters and Linters
 
 - See `tools/format/BUILD.bazel` for how to set up the formatter
 - See `.scalafmt.conf` for scalafmt configuration
+- See `.scalafix.conf` for scalafix syntactic rules
+- See `.scalafix.semantic.conf` for scalafix semantic rules
 
 5. Perform formatting using `aspect format`
+6. Perform linting using `aspect lint --config=lint`
+7. Perform semantic linting using `aspect lint --config=lint-semantic`
 
 ## Example Code
 
@@ -31,8 +37,16 @@ The `src/` directory contains example Scala files:
 ## Configuration Files
 
 - `.scalafmt.conf` - Scalafmt configuration file
+- `.scalafix.conf` - Scalafix syntactic configuration file
+- `.scalafix.semantic.conf` - Scalafix semantic configuration file
 - `maven_install.json` - Maven dependency lock file (auto-generated by rules_jvm_external)
 
+### Semantic rules note
+
+Semantic rules require SemanticDB. This example registers a Scala toolchain with
+`enable_semanticdb = True` and `semanticdb_bundle_in_jar = True`, which is required
+for scalafix to run in Bazel's sandbox.
+
 ### Generating maven_install.json
 
 After setting up your MODULE.bazel, generate the lock file: