Fix false negatives for exclamation and question mark in yml/plain-sc…

…alar rule

src/rules/plain-scalar.ts

@@ -4,7 +4,7 @@ import { createRule } from "../utils"
 
 const SYMBOLS = new Set([
     // mapping
-    "?",
+    // "?",
     ":",
     "{",
     "}",
@@ -22,9 +22,9 @@ const SYMBOLS = new Set([
     "|",
     "+",
     // tags
-    "!",
-    "<",
-    ">",
+    // "!",
+    // "<",
+    // ">",
     // directives
     "%",
     // quoted
@@ -56,21 +56,40 @@ export default createRule("plain-scalar", {
 
         const sourceCode = context.getSourceCode()
 
+        /* eslint-disable complexity -- X( */
         /**
          * Check if it can be converted to plain.
          */
         function canToPlain(
+            /* eslint-enable complexity -- X( */
             node: AST.YAMLDoubleQuotedScalar | AST.YAMLSingleQuotedScalar,
         ) {
+            if (node.value !== node.value.trim()) {
+                return false
+            }
             for (let index = 0; index < node.value.length; index++) {
                 const char = node.value[index]
                 if (SYMBOLS.has(char)) {
                     return false
                 }
-            }
-            if (/^\s*-\s+/u.test(node.value)) {
-                // “-” indicator
-                return false
+                if (index === 0) {
+                    if (char === "-" || char === "?") {
+                        const next = node.value[index + 1]
+                        if (next && !next.trim()) {
+                            // "-" indicator or "?" indicator
+                            return false
+                        }
+                    } else if (char === "!") {
+                        const next = node.value[index + 1]
+                        if (
+                            next &&
+                            (!next.trim() || next === "!" || next === "<")
+                        ) {
+                            // "!" indicator
+                            return false
+                        }
+                    }
+                }
             }
             const parent =
                 node.parent.type === "YAMLWithMeta"

tests/fixtures/rules/plain-scalar/invalid/exclamation-test-errors.json

@@ -0,0 +1,52 @@
+[
+    {
+        "message": "Must use plain style scalar.",
+        "line": 2,
+        "column": 1
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 2,
+        "column": 8
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 3,
+        "column": 1
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 3,
+        "column": 9
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 4,
+        "column": 1
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 4,
+        "column": 10
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 5,
+        "column": 1
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 5,
+        "column": 10
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 6,
+        "column": 1
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 6,
+        "column": 11
+    }
+]

tests/fixtures/rules/plain-scalar/invalid/exclamation-test-input.yml

@@ -0,0 +1,6 @@
+# {}
+"a!a": "b !b"
+"a!!a": "b !!b"
+"a!! a": "b !! b"
+"a!<a>": "b !<b>"
+"a! <a>": "b ! <b>"

tests/fixtures/rules/plain-scalar/invalid/exclamation-test-output.yml

@@ -0,0 +1,6 @@
+# plain-scalar/invalid/exclamation-test-input.yml
+a!a: b !b
+a!!a: b !!b
+a!! a: b !! b
+a!<a>: b !<b>
+a! <a>: b ! <b>

tests/fixtures/rules/plain-scalar/invalid/question-test-errors.json

@@ -0,0 +1,22 @@
+[
+    {
+        "message": "Must use plain style scalar.",
+        "line": 2,
+        "column": 1
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 4,
+        "column": 1
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 5,
+        "column": 1
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 6,
+        "column": 1
+    }
+]

tests/fixtures/rules/plain-scalar/invalid/question-test-input.yml

@@ -0,0 +1,6 @@
+# {}
+"?a": b
+"? a": b
+"?? a": b
+"a?a": b
+"a ? a": b

tests/fixtures/rules/plain-scalar/invalid/question-test-output.yml

@@ -0,0 +1,6 @@
+# plain-scalar/invalid/question-test-input.yml
+?a: b
+"? a": b
+?? a: b
+a?a: b
+a ? a: b

tests/fixtures/rules/plain-scalar/invalid/test-errors.json

@@ -0,0 +1,42 @@
+[
+    {
+        "message": "Must use plain style scalar.",
+        "line": 3,
+        "column": 3
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 3,
+        "column": 12
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 3,
+        "column": 22
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 3,
+        "column": 33
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 4,
+        "column": 3
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 4,
+        "column": 19
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 5,
+        "column": 3
+    },
+    {
+        "message": "Must use plain style scalar.",
+        "line": 5,
+        "column": 18
+    }
+]

tests/fixtures/rules/plain-scalar/invalid/test-input.yaml

@@ -0,0 +1,6 @@
+# {}
+{
+  "hello": "Hello!", "goodbye": "Goodbye!",
+  "good-morning": "Good Morning",
+  "how-are-you": "How are you doing?"
+}

tests/fixtures/rules/plain-scalar/invalid/test-output.yml

@@ -0,0 +1,6 @@
+# plain-scalar/invalid/test-input.yaml
+{
+  hello: Hello!, goodbye: Goodbye!,
+  good-morning: Good Morning,
+  how-are-you: How are you doing?
+}

tests/fixtures/rules/plain-scalar/valid/exclamation-test-input.yml

@@ -0,0 +1,6 @@
+# {}
+"!a": "!b"
+"!!a": "!!b"
+"!! a": "!! b"
+"!<a>": "!<b>"
+"! <a>": "! <b>"