[Resistor Duo analyzer (#127)] Add feedback to extract the constant to the top level if defined locally

src/analyzers/practice/resistor-color-duo/ResistorColorDuoSolution.ts

@@ -4,6 +4,7 @@ import {
   ExtractedVariable,
   extractExports,
   extractFunctions,
+  extractVariables,
   findAll,
   findFirst,
   findTopLevelConstants,
@@ -73,13 +74,18 @@ export class UnexpectedCallFound {
   ) {}
 }
 
+export class ShouldDefineTopLevelConstant {
+  constructor(public readonly name: string, public readonly value: string) {}
+}
+
 type Issue =
   | undefined
   | MissingExpectedCall
   | HelperNotOptimal
   | MethodNotFound
   | HelperCallNotFound
   | UnexpectedCallFound
+  | ShouldDefineTopLevelConstant
 
 class Constant {
   public readonly name: string
@@ -508,6 +514,15 @@ class Entry {
       }
     }
 
+    if (!constant) {
+      const issue = this.hasConstantDefinedInBody()
+      if (issue instanceof ShouldDefineTopLevelConstant) {
+        logger.log('~> found a constant that was not declared at the top level')
+        this.lastIssue_ = issue
+        return false
+      }
+    }
+
     if (this.hasOneMap) {
       logger.log('~> is a map solution')
       return this.isOptimalMapSolution(logger, this.body, constant, program)
@@ -1111,6 +1126,18 @@ class Entry {
     logger.log(`~> constant is not optimal`)
     return false
   }
+
+  private hasConstantDefinedInBody(): ShouldDefineTopLevelConstant | undefined {
+    const localConstants = extractVariables(this.body).filter(
+      (constant) =>
+        constant.init?.type === AST_NODE_TYPES.ArrayExpression ||
+        constant.init?.type === AST_NODE_TYPES.ObjectExpression
+    )
+    if (localConstants.length) {
+      const nameOfFirstConstant = localConstants[0].name || 'COLORS'
+      return new ShouldDefineTopLevelConstant(nameOfFirstConstant, '...')
+    }
+  }
 }
 
 export class ResistorColorDuoSolution {

src/analyzers/practice/resistor-color-duo/index.ts

@@ -21,6 +21,7 @@ import {
   MethodNotFound,
   MissingExpectedCall,
   ResistorColorDuoSolution,
+  ShouldDefineTopLevelConstant,
   UnexpectedCallFound,
 } from './ResistorColorDuoSolution'
 
@@ -120,6 +121,21 @@ const ISSUE_UNEXPECTED_CALL = factory<'unexpected' | 'expected'>`
   CommentType.Actionable
 )
 
+const PREFER_EXTRACTED_TOP_LEVEL_CONSTANT = factory<'value' | 'name'>`
+Instead of defining the constant _inside_ the function, consider extracting it
+to the top-level. Constants, functions, and classes that are not \`export\`ed,
+are not accessible from outside the file.
+
+\`\`\`javascript
+const ${'name'} = ${'value'}
+
+export const decodedValue = (...)
+\`\`\`
+`(
+  'javascript.resistor-color-duo.prefer_extracted_top_level_constant',
+  CommentType.Actionable
+)
+
 type Program = TSESTree.Program
 
 export class ResistorColorDuoAnalyzer extends IsolatedAnalyzerImpl {
@@ -275,6 +291,13 @@ export class ResistorColorDuoAnalyzer extends IsolatedAnalyzerImpl {
       }
 
       output.disapprove()
+    } else if (lastIssue instanceof ShouldDefineTopLevelConstant) {
+      output.add(
+        PREFER_EXTRACTED_TOP_LEVEL_CONSTANT({
+          name: lastIssue.name,
+          value: lastIssue.value,
+        })
+      )
     } else {
       this.logger.error(
         'The analyzer did not handle the issue: ' + JSON.stringify(lastIssue)