Use default js-yaml schema (palantir#4350)

This will change yaml parser to use the default schema, which allows
some additional Yaml types, see http://yaml.org/type/

Namely, this will allow the merge syntax, allowing users to define
common rules and then merge them into the typescript and javascript
rules.

Note: To do this, the options passed to yaml.safeLoad have been
removed since they are no longer required. The default safe schema
is what we want, and the strict: true is not a valid option, since
js-yaml removed it a while back, see here:
nodeca/js-yaml@e6bac15

src/configuration.ts

@@ -267,13 +267,7 @@ export function readConfigurationFile(filepath: string): RawConfigFile {
             if (resolvedConfigFileExt === ".json") {
                 return JSON.parse(stripComments(fileContent)) as RawConfigFile;
             } else {
-                return yaml.safeLoad(fileContent, {
-                    // Note: yaml.LoadOptions expects a schema value of type "any",
-                    // but this trips up the no-unsafe-any rule.
-                    // tslint:disable-next-line:no-unsafe-any
-                    schema: yaml.JSON_SCHEMA,
-                    strict: true,
-                }) as RawConfigFile;
+                return yaml.safeLoad(fileContent) as RawConfigFile;
             }
         } catch (e) {
             const error = e as Error;

test/config/tslint-with-merge.yaml

@@ -0,0 +1,18 @@
+commonRules: &common
+    rule-one:
+        severity: error
+    rule-two:
+        - true
+        - "common rule"
+jsRules:
+    <<: *common
+    rule-three:
+        - true
+        - "js rule"
+rules:
+    <<: *common
+    rule-one:
+        severity: warning
+    rule-three:
+        - true
+        - "ts rule"

test/configurationTests.ts

@@ -624,6 +624,41 @@ describe("Configuration", () => {
             assertRulesEqual(config.jsRules, expectedRules);
         });
 
+        it("can load .yaml files with merge key", () => {
+            const config = loadConfigurationFromPath("./test/config/tslint-with-merge.yaml");
+
+            const expectedRules = getEmptyRules();
+            expectedRules.set("rule-one", {
+                ruleArguments: undefined,
+                ruleSeverity: "warning",
+            });
+            expectedRules.set("rule-two", {
+                ruleArguments: ["common rule"],
+                ruleSeverity: "error",
+            });
+            expectedRules.set("rule-three", {
+                ruleArguments: ["ts rule"],
+                ruleSeverity: "error",
+            });
+
+            const expectedJsRules = getEmptyRules();
+            expectedJsRules.set("rule-one", {
+                ruleArguments: undefined,
+                ruleSeverity: "error",
+            });
+            expectedJsRules.set("rule-two", {
+                ruleArguments: ["common rule"],
+                ruleSeverity: "error",
+            });
+            expectedJsRules.set("rule-three", {
+                ruleArguments: ["js rule"],
+                ruleSeverity: "error",
+            });
+
+            assertRulesEqual(config.rules, expectedRules);
+            assertRulesEqual(config.jsRules, expectedJsRules);
+        });
+
         it("can load a built-in configuration", () => {
             const config = loadConfigurationFromPath("tslint:recommended");
             assert.strictEqual<RuleSeverity | undefined>(