config: Support the defaulting of rules in config (#587)

* config: Support the defaulting of rules in config

This PR implements an approach to rule defaulting described in:
#153 (comment)

Signed-off-by: Charlie Egan <charlie@styra.com>

* Address linter and refactor

Signed-off-by: Charlie Egan <charlie@styra.com>

* Add e2e test for config defaulting and flag use

Signed-off-by: Charlie Egan <charlie@styra.com>

* Add new notes for defaulting in README

Signed-off-by: Charlie Egan <charlie@styra.com>

---------

Signed-off-by: Charlie Egan <charlie@styra.com>

README.md

@@ -361,13 +361,34 @@ provided will be used to override the default configuration.
 
 ## Ignoring Rules
 
-If some rule doesn't align with your team's preferences, don't worry! Regal is not meant to be the law, and some rules
-may not make sense for your project, or parts of it. Regal provides several different ways to ignore rules, either
-entirely, or with more granularity.
+If one of Regal's rules doesn't align with your team's preferences, don't worry! Regal is not meant to be the law,
+and some rules may not make sense for your project, or parts of it.
+Regal provides several different methods to ignore rules with varying precedence.
+The available methods are (ranked highest to lowest precedence):
 
-### Ignoring a Rule Entirely
+- [Inline Ignore Directives](#inline-ignore-directives) cannot be overridden by any other method.
+- Enabling or Disabling Rules with CLI flags.
+  - Enabling or Disabling Rules with `--enable` and `--disable` CLI flags.
+  - Enabling or Disabling Rules with `--enable-category` and `--disable-category` CLI flags.
+  - Enabling or Disabling All Rules with `--enable-all` and `--disable-all` CLI flags.
+  - See [Ignoring Rules via CLI Flags](#ignoring-rules-via-cli-flags) for more details.
+- [Ignoring a Rule In Config](#ignoring-a-rule-in-config)
+- [Ignoring a Category In Config](#ignoring-a-category-in-config)
+- [Ignoring All Rules In Config](#ignoring-all-rules-in-config)
 
-If you want to ignore a rule entirely, set its level to `ignore` in the configuration file:
+In summary, the CLI flags will override any configuration provided in the file, and inline ignore directives for a
+specific line will override any other method.
+
+It's also possible to ignore messages on a per-file basis. The available methods are (ranked High to Lowest precedence):
+
+- Using the `--ignore-files` CLI flag.
+  See [Ignoring Rules via CLI Flags](#ignoring-rules-via-cli-flags).
+- [Ignoring Files Globally](#ignoring-files-globally) or
+  [Ignoring a Rule in Some Files](#ignoring-a-rule-in-some-files).
+
+### Ignoring a Rule In Config
+
+If you want to ignore a rule, set its level to `ignore` in the configuration file:
 
 ```yaml
 rules:
@@ -377,6 +398,34 @@ rules:
       level: ignore
 ```
 
+### Ignoring a Category In Config
+
+If you want to ignore a category of rules, set its default level to `ignore` in the configuration file:
+
+```yaml
+rules:
+  style:
+    default:
+      level: ignore
+```
+
+### Ignoring All Rules In Config
+
+If you want to ignore all rules, set the default level to `ignore` in the configuration file:
+
+```yaml
+rules:
+  default:
+    level: ignore
+  # then you can re-enable specific rules or categories
+  testing:
+    default:
+      level: error
+  style:
+    opa-fmt:
+      level: error
+```
+
 **Tip**: providing a comment on ignored rules is a good way to communicate why the decision was made.
 
 ### Ignoring a Rule in Some Files

e2e/cli_test.go

@@ -577,6 +577,80 @@ func TestMergeRuleConfigWithoutLevel(t *testing.T) {
 	expectExitCode(t, err, 3, &stdout, &stderr)
 }
 
+func TestConfigDefaultingWithDisableDirective(t *testing.T) {
+	t.Parallel()
+
+	stdout := bytes.Buffer{}
+	stderr := bytes.Buffer{}
+
+	cwd := testutil.Must(os.Getwd())(t)
+
+	err := regal(&stdout, &stderr)(
+		"lint",
+		"--disable-category=testing",
+		"--config-file",
+		cwd+filepath.FromSlash("/testdata/configs/defaulting.yaml"),
+		cwd+filepath.FromSlash("/testdata/defaulting"),
+	)
+
+	// ignored by flag ignore directive
+	if strings.Contains(stdout.String(), "print-or-trace-call") {
+		t.Errorf("expected stdout to not contain print-or-trace-call")
+		t.Log("stdout:\n", stdout.String())
+	}
+
+	// ignored by config
+	if strings.Contains(stdout.String(), "opa-fmt") {
+		t.Errorf("expected stdout to not contain print-or-trace-call")
+		t.Log("stdout:\n", stdout.String())
+	}
+
+	// this error should not be ignored
+	if !strings.Contains(stdout.String(), "top-level-iteration") {
+		t.Errorf("expected stdout to contain top-level-iteration")
+		t.Log("stdout:\n", stdout.String())
+	}
+
+	expectExitCode(t, err, 3, &stdout, &stderr)
+}
+
+func TestConfigDefaultingWithEnableDirective(t *testing.T) {
+	t.Parallel()
+
+	stdout := bytes.Buffer{}
+	stderr := bytes.Buffer{}
+
+	cwd := testutil.Must(os.Getwd())(t)
+
+	err := regal(&stdout, &stderr)(
+		"lint",
+		"--enable-all",
+		"--config-file",
+		cwd+filepath.FromSlash("/testdata/configs/defaulting.yaml"),
+		cwd+filepath.FromSlash("/testdata/defaulting"),
+	)
+
+	// re-enabled by flag enable directive
+	if !strings.Contains(stdout.String(), "print-or-trace-call") {
+		t.Errorf("expected stdout to contain print-or-trace-call")
+		t.Log("stdout:\n", stdout.String())
+	}
+
+	// re-enabled by flag enable directive
+	if !strings.Contains(stdout.String(), "opa-fmt") {
+		t.Errorf("expected stdout to contain opa-fmt")
+		t.Log("stdout:\n", stdout.String())
+	}
+
+	// this error should not be ignored
+	if !strings.Contains(stdout.String(), "top-level-iteration") {
+		t.Errorf("expected stdout to contain top-level-iteration")
+		t.Log("stdout:\n", stdout.String())
+	}
+
+	expectExitCode(t, err, 3, &stdout, &stderr)
+}
+
 func TestLintWithCustomCapabilitiesAndUnmetRequirement(t *testing.T) {
 	t.Parallel()
 

e2e/testdata/configs/defaulting.yaml

@@ -0,0 +1,11 @@
+rules:
+  default:
+    level: ignore
+  bugs:
+    default:
+      level: error
+    rule-shadows-builtin:
+      level: ignore
+  testing:
+    print-or-trace-call:
+      level: error

e2e/testdata/defaulting/example.rego

@@ -0,0 +1,9 @@
+package p
+import rego.v1
+boo := input.hoo[_]
+ opa_fmt := "fail"
+or := 1
+
+allow  if {
+  print("hello")
+}