[steps][3/5] Add action interpolation helpers

packages/steps/src/ActionExpander.ts

@@ -26,7 +26,11 @@ import { BuildStepEnv } from './BuildStepEnv';
 import { BuildConfigError } from './errors';
 import { duplicates } from './utils/expodash/duplicates';
 import { isActionPath, parseActionPath } from './utils/localActions';
-import { createBuildStepOutputsFromDefinition, getShellStepDisplayName } from './utils/step';
+import {
+  createBuildStepOutputsFromDefinition,
+  getShellStepDisplayName,
+  mergeEnv,
+} from './utils/step';
 
 const MAX_ACTION_NESTING_DEPTH = 10;
 
@@ -328,10 +332,3 @@ export class ActionExpander {
     return { stepIdMap, newIds };
   }
 }
-
-function mergeEnv(base?: BuildStepEnv, overrides?: BuildStepEnv): BuildStepEnv | undefined {
-  if (!base && !overrides) {
-    return undefined;
-  }
-  return { ...base, ...overrides };
-}

packages/steps/src/utils/__tests__/actionInterpolation-test.ts

@@ -0,0 +1,93 @@
+import { JobInterpolationContext } from '@expo/eas-build-job';
+
+import { createGlobalContextMock } from '../../__tests__/utils/context';
+import {
+  containsUnresolvedTemplateReference,
+  resolveInterpolatedTarget,
+  stringifyInterpolatedResult,
+} from '../actionInterpolation';
+
+function contextWith({
+  steps = {},
+  env = {},
+}: {
+  steps?: JobInterpolationContext['steps'];
+  env?: Record<string, string | undefined>;
+} = {}): JobInterpolationContext {
+  const globalCtx = createGlobalContextMock();
+  return { ...globalCtx.getInterpolationContext(), steps, env } as JobInterpolationContext;
+}
+
+describe(resolveInterpolatedTarget, () => {
+  const neverResolve = (): string => '';
+
+  it('passes literal targets through unchanged', () => {
+    expect(resolveInterpolatedTarget('literal', contextWith(), neverResolve)).toBe('literal');
+  });
+
+  it('resolves ${{ }} expressions against the context', () => {
+    expect(
+      resolveInterpolatedTarget(
+        '${{ env.FOO }}',
+        contextWith({ env: { FOO: 'bar' } }),
+        neverResolve
+      )
+    ).toBe('bar');
+  });
+
+  it('routes legacy ${ steps.* } references through the provided resolver', () => {
+    const resolver = (path: string): string => (path === 'steps.read.version' ? '1.2.3' : '');
+    expect(resolveInterpolatedTarget('v${ steps.read.version }', contextWith(), resolver)).toBe(
+      'v1.2.3'
+    );
+  });
+
+  it('returns non-string results as-is, without touching the legacy resolver', () => {
+    const context = contextWith();
+    const resolver = jest.fn<string, [string]>();
+    expect(resolveInterpolatedTarget('${{ fromJSON(\'{"a":1}\') }}', context, resolver)).toEqual({
+      a: 1,
+    });
+    expect(resolver).not.toHaveBeenCalled();
+  });
+});
+
+describe(stringifyInterpolatedResult, () => {
+  it('renders nullish values as an empty string and objects as JSON', () => {
+    expect(stringifyInterpolatedResult(undefined)).toBe('');
+    expect(stringifyInterpolatedResult(null)).toBe('');
+    expect(stringifyInterpolatedResult({ a: 1 })).toBe('{"a":1}');
+    expect(stringifyInterpolatedResult(3)).toBe('3');
+  });
+});
+
+describe(containsUnresolvedTemplateReference, () => {
+  it('recognizes ${{ }} template references', () => {
+    expect(containsUnresolvedTemplateReference('${{ steps.a.outputs.v }}')).toBe(true);
+    expect(containsUnresolvedTemplateReference(' ${{ steps.a.outputs.v }} ')).toBe(true);
+    expect(containsUnresolvedTemplateReference('${{ steps.a.outputs.v }}\n')).toBe(true);
+  });
+
+  it('recognizes ${{ }} template references embedded in a larger string', () => {
+    expect(containsUnresolvedTemplateReference('${{ steps.a.outputs.v }}px')).toBe(true);
+    expect(containsUnresolvedTemplateReference('${{ inputs.p }}-variant')).toBe(true);
+    expect(containsUnresolvedTemplateReference('a-${{ env.FOO }}-b')).toBe(true);
+  });
+
+  it('recognizes legacy ${ } step output references', () => {
+    expect(containsUnresolvedTemplateReference('${ steps.a.outputs.v }')).toBe(true);
+    expect(containsUnresolvedTemplateReference('${ steps.a.v }')).toBe(true);
+    expect(containsUnresolvedTemplateReference('a-${ steps.a.outputs.v }-b')).toBe(true);
+  });
+
+  it('does not recognize non-step legacy ${ } spans', () => {
+    expect(containsUnresolvedTemplateReference('${ inputs.count }')).toBe(false);
+    expect(containsUnresolvedTemplateReference('echo ${FOO:-bar}')).toBe(false);
+  });
+
+  it('returns false for plain strings and non-strings', () => {
+    expect(containsUnresolvedTemplateReference('plain')).toBe(false);
+    expect(containsUnresolvedTemplateReference(5)).toBe(false);
+    expect(containsUnresolvedTemplateReference(undefined)).toBe(false);
+  });
+});

packages/steps/src/utils/actionInterpolation.ts

@@ -0,0 +1,42 @@
+import { JobInterpolationContext } from '@expo/eas-build-job';
+
+import { BUILD_STEP_OUTPUT_EXPRESSION_REGEXP, interpolateWithOutputs } from './template';
+import { interpolateJobContext } from '../interpolation';
+
+// Non-string results skip the legacy resolver: `${ steps.* }` only appears inside strings.
+export function resolveInterpolatedTarget(
+  target: unknown,
+  context: JobInterpolationContext,
+  legacyResolver: (path: string) => string
+): unknown {
+  const resolved = interpolateJobContext({ target, context });
+  if (typeof resolved === 'string') {
+    return interpolateWithOutputs(resolved, legacyResolver);
+  }
+  return resolved;
+}
+
+export function stringifyInterpolatedResult(value: unknown): string {
+  if (value === undefined || value === null) {
+    return '';
+  }
+  if (typeof value === 'object') {
+    return JSON.stringify(value);
+  }
+  return String(value);
+}
+
+export function stringifyOptionalInterpolatedResult(value: unknown): string | undefined {
+  if (value === undefined || value === null) {
+    return undefined;
+  }
+  return stringifyInterpolatedResult(value);
+}
+
+// Matches `${{ }}` or legacy `${ steps.* }` only; shell `${FOO:-bar}` / `${ inputs.* }` are excluded.
+export function containsUnresolvedTemplateReference(value: unknown): boolean {
+  return (
+    typeof value === 'string' &&
+    (value.includes('${{') || BUILD_STEP_OUTPUT_EXPRESSION_REGEXP.test(value))
+  );
+}

packages/steps/src/utils/step.ts

@@ -1,8 +1,16 @@
 import { ShellStep } from '@expo/eas-build-job';
 
 import { BuildStepGlobalContext } from '../BuildStepContext';
+import { BuildStepEnv } from '../BuildStepEnv';
 import { BuildStepOutput } from '../BuildStepOutput';
 
+export function mergeEnv(base?: BuildStepEnv, overrides?: BuildStepEnv): BuildStepEnv | undefined {
+  if (!base && !overrides) {
+    return undefined;
+  }
+  return { ...base, ...overrides };
+}
+
 export function getShellStepDisplayName(step: ShellStep): string {
   return (
     step.name ??