Affordances for suggestions/snippets (#13)

Author: davidjgoss

CHANGELOG.md

@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- Add `pickleStep` to `UndefinedError` ([#13](https://github.com/cucumber/javascript-core/pull/13))
+- Add `getExpressionGenerator()` to `SupportCodeLibrary` ([#13](https://github.com/cucumber/javascript-core/pull/13))
 
 ## [0.4.1] - 2025-09-05
 ### Fixed

cucumber-core.api.md

@@ -6,13 +6,15 @@
 
 import { Argument } from '@cucumber/cucumber-expressions';
 import { CucumberExpression } from '@cucumber/cucumber-expressions';
+import { CucumberExpressionGenerator } from '@cucumber/cucumber-expressions';
 import { Envelope } from '@cucumber/messages';
 import { GherkinDocument } from '@cucumber/messages';
 import { Hook } from '@cucumber/messages';
 import { IdGenerator } from '@cucumber/messages';
 import { NamingStrategy } from '@cucumber/query';
 import parse from '@cucumber/tag-expressions';
 import { Pickle } from '@cucumber/messages';
+import { PickleStep } from '@cucumber/messages';
 import { RegularExpression } from '@cucumber/cucumber-expressions';
 import { SourceReference } from '@cucumber/messages';
 import { StepDefinition } from '@cucumber/messages';
@@ -179,6 +181,7 @@ export interface SupportCodeLibrary {
     findAllStepsBy(text: string): ReadonlyArray<MatchedStep>;
     getAllAfterAllHooks(): ReadonlyArray<DefinedTestRunHook>;
     getAllBeforeAllHooks(): ReadonlyArray<DefinedTestRunHook>;
+    getExpressionGenerator(): CucumberExpressionGenerator;
     toEnvelopes(): ReadonlyArray<Envelope>;
 }
 
@@ -203,7 +206,9 @@ export interface TestPlanOptions {
 
 // @public
 export class UndefinedError extends Error {
-    constructor(text: string);
+    constructor(pickleStep: PickleStep);
+    // (undocumented)
+    readonly pickleStep: PickleStep;
 }
 
 // @public

src/SupportCodeBuilderImpl.ts

@@ -275,6 +275,7 @@ export class SupportCodeBuilderImpl implements SupportCodeBuilder {
 
   build() {
     return new SupportCodeLibraryImpl(
+      this.parameterTypeRegistry,
       this.buildParameterTypes(),
       this.buildSteps(),
       this.buildUndefinedParameterTypes(),

src/SupportCodeLibraryImpl.ts

@@ -1,3 +1,5 @@
+import { CucumberExpressionGenerator, ParameterTypeRegistry } from '@cucumber/cucumber-expressions'
+
 import {
   DefinedParameterType,
   DefinedStep,
@@ -13,6 +15,7 @@ import {
  */
 export class SupportCodeLibraryImpl implements SupportCodeLibrary {
   constructor(
+    private readonly parameterTypeRegistry: ParameterTypeRegistry,
     private readonly parameterTypes: ReadonlyArray<DefinedParameterType> = [],
     private readonly steps: ReadonlyArray<DefinedStep> = [],
     private readonly undefinedParameterTypes: ReadonlyArray<UndefinedParameterType> = [],
@@ -36,6 +39,10 @@ export class SupportCodeLibraryImpl implements SupportCodeLibrary {
     return results
   }
 
+  getExpressionGenerator(): CucumberExpressionGenerator {
+    return new CucumberExpressionGenerator(() => this.parameterTypeRegistry.parameterTypes)
+  }
+
   findAllBeforeHooksBy(tags: ReadonlyArray<string>) {
     return this.beforeHooks.filter((def) => {
       if (def.tags) {

src/UndefinedError.ts

@@ -1,9 +1,11 @@
+import { PickleStep } from '@cucumber/messages'
+
 /**
  * Represents an error that occurs when no step definitions are found matching the text of a step
  * @public
  */
 export class UndefinedError extends Error {
-  constructor(text: string) {
-    super(`No matching step definitions found for text "${text}"`)
+  constructor(public readonly pickleStep: PickleStep) {
+    super(`No matching step definitions found for text "${pickleStep.text}"`)
   }
 }

src/buildSupportCode.spec.ts

@@ -336,6 +336,15 @@ describe('buildSupportCode', () => {
     })
   })
 
+  describe('expression generator', () => {
+    it('returns a cucumber expression generator primed with the parameter type registry', () => {
+      const library = buildSupportCode({ newId }).build()
+      const expressionGenerator = library.getExpressionGenerator()
+      const expressions = expressionGenerator.generateExpressions('I have 17 cukes in my belly')
+      expect(expressions.length).to.eq(2)
+    })
+  })
+
   describe('test run hooks', () => {
     let library: SupportCodeLibrary
     beforeEach(() => {

src/makeTestPlan.spec.ts

@@ -168,7 +168,12 @@ describe('makeTestPlan', () => {
         }
       )
 
-      expect(() => result.testCases[0].testSteps[0].prepare(undefined)).to.throw(UndefinedError)
+      try {
+        result.testCases[0].testSteps[0].prepare(undefined)
+      } catch (err: any) {
+        expect(err).to.be.instanceOf(UndefinedError)
+        expect(err.pickleStep).to.eq(pickles[0].steps[0])
+      }
     })
 
     it('matches and prepares a step without parameters', () => {

src/makeTestPlan.ts

@@ -178,7 +178,7 @@ function fromPickleSteps(
       always: false,
       prepare(thisArg) {
         if (matched.length < 1) {
-          throw new UndefinedError(pickleStep.text)
+          throw new UndefinedError(pickleStep)
         } else if (matched.length > 1) {
           throw new AmbiguousError(
             pickleStep.text,

src/types.ts

@@ -1,4 +1,9 @@
-import { Argument, CucumberExpression, RegularExpression } from '@cucumber/cucumber-expressions'
+import {
+  Argument,
+  CucumberExpression,
+  CucumberExpressionGenerator,
+  RegularExpression,
+} from '@cucumber/cucumber-expressions'
 import {
   Envelope,
   GherkinDocument,
@@ -329,6 +334,10 @@ export interface SupportCodeLibrary {
    * Find all step definitions whose expression is a match for the given text
    */
   findAllStepsBy(text: string): ReadonlyArray<MatchedStep>
+  /**
+   * Get a generator for Cucumber Expressions based on the currently defined parameter types
+   */
+  getExpressionGenerator(): CucumberExpressionGenerator
   /**
    * Get all BeforeAll hooks
    */