fix: don't run eslint with zero files to check

Fixes #368

example/src/BUILD.bazel

@@ -1,8 +1,10 @@
 load("@aspect_rules_lint//format:defs.bzl", "format_test")
+load("@aspect_rules_swc//swc:defs.bzl", "swc")
 load("@aspect_rules_ts//ts:defs.bzl", "ts_config", "ts_project")
 load("@io_bazel_rules_go//go:def.bzl", "go_binary")
 load("@rules_kotlin//kotlin:jvm.bzl", "kt_jvm_library")
 load("@rules_proto//proto:defs.bzl", "proto_library")
+load("//tools/lint:linters.bzl", "eslint_test")
 
 package(default_visibility = ["//visibility:public"])
 
@@ -35,13 +37,19 @@ ts_project(
     name = "ts",
     srcs = ["file.ts"],
     declaration = True,
-    transpiler = "tsc",
+    transpiler = swc,
     deps = [
         ":ts_dep",
         "//:node_modules/dayjs",
     ],
 )
 
+# Regression test for https://github.com/aspect-build/rules_lint/issues/368
+eslint_test(
+    name = "eslint_empty_report",
+    srcs = [":ts"],
+)
+
 proto_library(
     name = "unused",
     srcs = ["unused.proto"],

example/src/subdir/BUILD.bazel

@@ -1,5 +1,4 @@
 load("@aspect_rules_js//js:defs.bzl", "js_library")
-load("@aspect_rules_swc//swc:defs.bzl", "swc")
 load("@aspect_rules_ts//ts:defs.bzl", "ts_project")
 
 exports_files(["ruff.toml"])
@@ -18,9 +17,7 @@ ts_project(
     name = "ts",
     srcs = ["test.ts"],
     declaration = True,
-    # verify that even when the macro expands to have js_library targets
-    # we don't try to lint the output javascript files
-    transpiler = swc,
+    transpiler = "tsc",
     tsconfig = "//src:tsconfig",
     deps = [
         "//:node_modules/@types/node",

example/test/BUILD.bazel

@@ -96,7 +96,12 @@ pmd_test(
 
 eslint_test(
     name = "eslint",
-    srcs = ["//src:ts"],
+    # NB: we must lint the `ts_typings` target that has the .ts files in srcs,
+    # not "//src:ts" which is just a js_library re-export.
+    # For end users it's not obvious that you have to "see inside" the macro to know
+    # which ts_project output target to lint.
+    # See https://github.com/aspect-build/rules_lint/issues/369
+    srcs = ["//src:ts_typings"],
     # Expected to fail based on current content of the file.
     # Normally you'd fix the file instead of tagging this test.
     tags = ["manual"],

lint/eslint.bzl

@@ -55,7 +55,7 @@ See the [react example](https://github.com/bazelbuild/examples/blob/b498bb106b20
 
 load("@aspect_bazel_lib//lib:copy_to_bin.bzl", "COPY_FILE_TO_BIN_TOOLCHAINS", "copy_files_to_bin_actions")
 load("@aspect_rules_js//js:libs.bzl", "js_lib_helpers")
-load("//lint/private:lint_aspect.bzl", "LintOptionsInfo", "filter_srcs", "output_files", "patch_and_output_files", "should_visit")
+load("//lint/private:lint_aspect.bzl", "LintOptionsInfo", "filter_srcs", "noop_lint_action", "output_files", "patch_and_output_files", "should_visit")
 
 _MNEMONIC = "AspectRulesLintESLint"
 
@@ -214,6 +214,10 @@ def _eslint_aspect_impl(target, ctx):
     # 2: Force 256 color support even when a tty isn't detected
     color_env = {"FORCE_COLOR": "2"} if ctx.attr._options[LintOptionsInfo].color else {}
 
+    if len(files_to_lint) == 0:
+        noop_lint_action(ctx, outputs)
+        return [info]
+
     # eslint can produce a patch file at the same time it reports the unpatched violations
     if hasattr(outputs, "patch"):
         eslint_fix(ctx, ctx.executable, files_to_lint, outputs.patch, outputs.human.out, outputs.human.exit_code, format = ctx.attr._stylish_formatter, env = color_env)

lint/private/lint_aspect.bzl

@@ -129,8 +129,9 @@ def filter_srcs(rule):
 def noop_lint_action(ctx, outputs):
     """Action that creates expected outputs when no files are provided to a lint action.
 
-    This is needed for linters that error when they are given no srcs to inspect.
-    It is also a performance optimisation in other cases.
+    This is needed for a linter that doel the wrong thing when given zero srcs to inspect,
+    for example it might as error or try to lint all files it can find.
+    It is also a performance optimisation in other cases so we use this everywhere.
 
     Args:
         ctx: Bazel Rule or Aspect evaluation context
@@ -144,12 +145,12 @@ def noop_lint_action(ctx, outputs):
 
     # NB: if we write JSON machine-readable outputs, then an empty file won't be appropriate
     if outputs.human.exit_code:
-      commands.append("echo 0 > {}".format(outputs.human.exit_code.path))
-      outs += [outputs.human.exit_code]
+        commands.append("echo 0 > {}".format(outputs.human.exit_code.path))
+        outs.append(outputs.human.exit_code)
 
     if outputs.machine.exit_code:
-      commands.append("echo 0 > {}".format(outputs.machine.exit_code.path))
-      outs += [outputs.machine.exit_code]
+        commands.append("echo 0 > {}".format(outputs.machine.exit_code.path))
+        outs.append(outputs.machine.exit_code)
 
     if hasattr(outputs, "patch"):
         commands.append("touch {}".format(outputs.patch.path))