fix(linter): support bare true/false and integer literals in rules:if:

GitLab CI expressions allow unquoted true, false, and integers as
comparison operands (all treated as their string representations):

  $GATEWAY_ENABLED == true    (equivalent to == "true")
  $FEATURE_FLAG == false      (equivalent to == "false")
  $PARALLEL == 4              (equivalent to == "4")
  $ENABLED == 1 / == 0

Previously these fell through to permissive true because parseValue
only recognised $VAR, "${VAR}", quoted strings, and null. Added:
  - true/false keyword branch → returns "true"/"false"
  - integer literal branch (digits only) → returns decimal string

All three new forms are correctly excluded from longer identifier
prefixes (identByte boundary check). Adds 8 new unit tests.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -9,11 +9,13 @@ This project uses [Semantic Versioning](https://semver.org).
 
 ### Added
 
-- **`rules:if:` expression evaluator improvements** — four correctness fixes to the GitLab CI expression parser:
+- **`rules:if:` expression evaluator improvements** — six correctness fixes to the GitLab CI expression parser:
   - **Multi-line expressions** — newlines (`\n`, `\r`) are now treated as whitespace between tokens, so block-scalar `if:` values (e.g. `if: | ...`) and folded YAML scalars with `||`/`&&` on a continuation line are parsed correctly instead of falling back to permissive `true`.
   - **`${VAR}` curly-brace variable syntax** — `${CI_COMMIT_BRANCH}` is now equivalent to `$CI_COMMIT_BRANCH` everywhere a value is expected.
   - **Regex flags** — `/pattern/i`, `/pattern/m`, `/pattern/s` are now honoured; the `i` flag (case-insensitive) is translated to Go's `(?i)` prefix before compiling. Unknown flags are silently ignored.
   - **Variable as regex RHS** — `$BRANCH =~ $PATTERN` where `$PATTERN` holds a `/regex/[flags]` string is now evaluated by extracting and compiling the pattern from the variable's value; if the value is empty or does not look like a regex literal the expression falls back to permissive `true`.
+  - **`true` / `false` keywords** — bare `true` and `false` (without quotes) are now recognised as the string values `"true"` and `"false"`, matching GitLab CI's own behaviour. `$GATEWAY_ENABLED == true` and `$FEATURE_FLAG == false` now evaluate correctly.
+  - **Integer literals** — bare integers (e.g. `$PARALLEL == 4`, `$ENABLED == 1`, `$DISABLED == 0`) are now parsed as their decimal string representations and compared accordingly.
 
 - **File and line numbers on findings** — every finding now includes the source file and line where the job is defined, e.g. `[ERROR] job "deploy" (src/deploy.yml:14): …`. For jobs that come from local or fetched includes the file reflects the include source. Pipeline-level findings (workflow rules, missing stages) reference the root pipeline file.
 

internal/cicontext/eval.go

@@ -231,8 +231,10 @@ func (p *exprParser) parseRegexRHS() (pat string, ok bool, permissive bool) {
 	return "", false, false
 }
 
-// parseValue reads $VAR, ${VAR}, "string", 'string', or null.
+// parseValue reads $VAR, ${VAR}, "string", 'string', null, true, false, or an
-// null and undefined variables both produce an empty string.
+// integer literal. null and undefined variables both produce an empty string.
+// true/false and integers produce their string representations (GitLab CI
+// compares all values as strings).
 func (p *exprParser) parseValue() (string, bool) {
 	p.skipWS()
 
@@ -254,12 +256,18 @@ func (p *exprParser) parseValue() (string, bool) {
 		return p.vars(name), true
 	}
 
-	// null keyword — must not be a prefix of a longer identifier.
+	// Keywords and string literals must not be prefixes of longer identifiers.
-	if p.startsWith("null") {
+	for _, kw := range []struct{ tok, val string }{
-		end := p.pos + 4
+		{"null", ""},
-		if end >= len(p.s) || !isIdentByte(p.s[end]) {
+		{"true", "true"},
-			p.pos += 4
+		{"false", "false"},
-			return "", true // null → empty string
+	} {
+		if p.startsWith(kw.tok) {
+			end := p.pos + len(kw.tok)
+			if end >= len(p.s) || !isIdentByte(p.s[end]) {
+				p.pos += len(kw.tok)
+				return kw.val, true
+			}
 		}
 	}
 
@@ -267,6 +275,15 @@ func (p *exprParser) parseValue() (string, bool) {
 		return p.parseStringLiteral()
 	}
 
+	// Integer literal — returned as its decimal string for string comparison.
+	if p.peek() >= '0' && p.peek() <= '9' {
+		start := p.pos
+		for p.pos < len(p.s) && p.s[p.pos] >= '0' && p.s[p.pos] <= '9' {
+			p.pos++
+		}
+		return p.s[start:p.pos], true
+	}
+
 	return "", false
 }
 

internal/cicontext/eval_test.go

@@ -103,6 +103,20 @@ func TestEvalIf(t *testing.T) {
 		{"var regex rhs plain permissive", `$CI_COMMIT_BRANCH =~ $PLAIN_PATTERN`, true},
 		{"var regex rhs not match", `$CI_COMMIT_BRANCH !~ $BRANCH_PATTERN`, false},
 
+		// ── Bare true/false keywords ─────────────────────────────────────────
+		// GitLab CI treats true/false as the string values "true"/"false".
+		{"bare true match", `$CI_PIPELINE_SOURCE == true`, false},       // "push" != "true"
+		{"bare false match", `$CI_COMMIT_TAG == false`, false},           // "" != "false"
+		{"bare true var set to true", `$DEPLOY_ENV == true`, false},      // "staging" != "true"
+		{"bare false neq", `$CI_COMMIT_BRANCH != false`, true},           // "develop" != "false"
+		{"bare true in compound", `$CI_COMMIT_BRANCH != null && $CI_COMMIT_TAG == false`, false},
+
+		// ── Integer literals ──────────────────────────────────────────────────
+		// Compared as decimal strings (GitLab CI converts integers to strings).
+		{"int eq match", `$CI_PIPELINE_SOURCE != 0`, true},  // "push" != "0"
+		{"int eq no match", `$CI_COMMIT_TAG == 0`, false},    // "" != "0"
+		{"int in compound", `$CI_COMMIT_BRANCH != null && $CI_COMMIT_BRANCH != 0`, true},
+
 		// ── Permissive fallback ───────────────────────────────────────────────
 		{"unparseable returns true", `this is not valid syntax %%%`, true},
 		{"empty expr returns true", ``, true},