fix: allow runModel to proceed without error when inputs array is empty

packages/runtime-async/tests/runner.spec.ts

@@ -172,6 +172,16 @@ describe.each([
     expect(outOutputs.getSeriesForVar('_output_2')!.points).toEqual([p(2000, 4), p(2001, 5), p(2002, 6)])
   })
 
+  it('should run the model (with empty inputs array)', async () => {
+    expect(runner).toBeDefined()
+    const inOutputs = runner.createOutputs()
+    const outOutputs = await runner.runModel([], inOutputs)
+    expect(outOutputs).toBeDefined()
+    expect(outOutputs.runTimeInMillis).toBeGreaterThan(0)
+    expect(outOutputs.getSeriesForVar('_output_1')!.points).toEqual([p(2000, 1), p(2001, 2), p(2002, 3)])
+    expect(outOutputs.getSeriesForVar('_output_2')!.points).toEqual([p(2000, 4), p(2001, 5), p(2002, 6)])
+  })
+
   it('should run the model (with lookup overrides)', async () => {
     const listing = new ModelListing(json)
 

packages/runtime/src/js-model/js-model.ts

@@ -103,7 +103,7 @@ function runJsModel(
   timeStep: number,
   saveFreq: number,
   numSavePoints: number,
-  inputs: Float64Array,
+  inputs: Float64Array | undefined,
   outputs: Float64Array,
   outputIndices: Int32Array | undefined,
   lookups: LookupDef[] | undefined,
@@ -131,7 +131,7 @@ function runJsModel(
     }
   }
 
-  if (inputs.length > 0) {
+  if (inputs?.length > 0) {
     // Set the user-defined input values.  This needs to happen after `initConstants`
     // since the input values will override the default constant values.
     model.setInputs(index => inputs[index])

packages/runtime/src/model-runner/synchronous-model-runner.spec.ts

@@ -45,7 +45,9 @@ function createMockWasmModule(): MockWasmModule {
     outputVarIds: ['_output_1', '_output_2'],
     onRunModel: (inputs, outputs, lookups, outputIndices) => {
       // Verify inputs
-      expect(inputs).toEqual(new Float64Array([7, 8, 9]))
+      if (inputs.length > 0) {
+        expect(inputs).toEqual(new Float64Array([7, 8, 9]))
+      }
 
       if (lookups.size > 0) {
         // Pretend that outputs are derived from lookup data
@@ -130,6 +132,16 @@ describe.each([
     expect(outOutputs.getSeriesForVar('_output_2').points).toEqual([p(2000, 4), p(2001, 5), p(2002, 6)])
   })
 
+  it('should run the model (with empty inputs array)', async () => {
+    expect(runner).toBeDefined()
+    const inOutputs = runner.createOutputs()
+    const outOutputs = await runner.runModel([], inOutputs)
+    expect(outOutputs).toBeDefined()
+    expect(outOutputs.runTimeInMillis).toBeGreaterThan(0)
+    expect(outOutputs.getSeriesForVar('_output_1').points).toEqual([p(2000, 1), p(2001, 2), p(2002, 3)])
+    expect(outOutputs.getSeriesForVar('_output_2').points).toEqual([p(2000, 4), p(2001, 5), p(2002, 6)])
+  })
+
   it('should run the model (with lookup overrides)', async () => {
     const json = `
 {

packages/runtime/src/runnable-model/base-runnable-model.ts

@@ -9,7 +9,7 @@ import type { RunnableModel } from './runnable-model'
  * @hidden This is not part of the public API; for internal use only.
  */
 export type OnRunModelFunc = (
-  inputs: Float64Array,
+  inputs: Float64Array | undefined,
   outputs: Float64Array,
   options?: {
     outputIndices?: Int32Array

packages/runtime/src/runnable-model/buffered-run-model-params.spec.ts

@@ -142,8 +142,11 @@ describe('BufferedRunModelParams', () => {
     const inputs = [1, 2, 3]
     const outputs = new Outputs(['_x', '_y'], 2000, 2002, 1)
 
-    const params = new BufferedRunModelParams()
-    params.updateFromParams(inputs, outputs)
+    const runnerParams = new BufferedRunModelParams()
+    const workerParams = new BufferedRunModelParams()
+
+    runnerParams.updateFromParams(inputs, outputs)
+    workerParams.updateFromEncodedBuffer(runnerParams.getEncodedBuffer())
 
     let array: Float64Array
     const create = (numElements: number) => {
@@ -152,17 +155,27 @@ describe('BufferedRunModelParams', () => {
     }
 
     // Verify case where existing array is undefined
-    params.copyInputs(undefined, create)
+    workerParams.copyInputs(undefined, create)
     expect(array).toEqual(new Float64Array([1, 2, 3]))
 
     // Verify case where existing array is too small
     array = new Float64Array(2)
-    params.copyInputs(array, create)
+    workerParams.copyInputs(array, create)
     expect(array).toEqual(new Float64Array([1, 2, 3]))
 
     // Verify case where existing array is large enough
     array = new Float64Array([6, 6, 6, 6])
-    params.copyInputs(array, create)
+    workerParams.copyInputs(array, create)
+    expect(array).toEqual(new Float64Array([1, 2, 3, 6]))
+
+    // Verify case where params are updated with an empty inputs array.  Note that
+    // it is expected that the existing data is retained in the destination array;
+    // it is up to the calling code to clear or ignore that existing data.
+    runnerParams.updateFromParams([], outputs)
+    runnerParams.copyInputs(array, create)
+    expect(array).toEqual(new Float64Array([1, 2, 3, 6]))
+    workerParams.updateFromEncodedBuffer(runnerParams.getEncodedBuffer())
+    workerParams.copyInputs(array, create)
     expect(array).toEqual(new Float64Array([1, 2, 3, 6]))
   })
 
@@ -172,8 +185,11 @@ describe('BufferedRunModelParams', () => {
     const normalOutputs = new Outputs(['_x', '_y'], 2000, 2002, 1)
     const implOutputs = listing.deriveOutputs(normalOutputs, ['_x', '_a', '_b'])
 
-    const params = new BufferedRunModelParams()
-    params.updateFromParams(inputs, implOutputs)
+    const runnerParams = new BufferedRunModelParams()
+    const workerParams = new BufferedRunModelParams()
+
+    runnerParams.updateFromParams(inputs, implOutputs)
+    workerParams.updateFromEncodedBuffer(runnerParams.getEncodedBuffer())
 
     const expectedIndices = new Int32Array([
       // _x
@@ -193,17 +209,17 @@ describe('BufferedRunModelParams', () => {
     }
 
     // Verify case where existing array is undefined
-    params.copyOutputIndices(undefined, create)
+    workerParams.copyOutputIndices(undefined, create)
     expect(array).toEqual(expectedIndices)
 
     // Verify case where existing array is too small
     array = new Int32Array(2)
-    params.copyOutputIndices(array, create)
+    workerParams.copyOutputIndices(array, create)
     expect(array).toEqual(expectedIndices)
 
     // Verify case where existing array is large enough
     array = new Int32Array(20).fill(6)
-    params.copyOutputIndices(array, create)
+    workerParams.copyOutputIndices(array, create)
     expect(array).toEqual(
       new Int32Array([
         // _x
@@ -225,9 +241,10 @@ describe('BufferedRunModelParams', () => {
     const outputs = new Outputs(['_x', '_y'], 2000, 2002, 1)
 
     const runnerParams = new BufferedRunModelParams()
-    runnerParams.updateFromParams(inputs, outputs)
-
     const workerParams = new BufferedRunModelParams()
+
+    // Run once
+    runnerParams.updateFromParams(inputs, outputs)
     workerParams.updateFromEncodedBuffer(runnerParams.getEncodedBuffer())
 
     // Pretend that the model writes the following values to its outputs buffer then

packages/runtime/src/runnable-model/buffered-run-model-params.ts

@@ -107,6 +107,12 @@ export class BufferedRunModelParams implements RunModelParams {
 
   // from RunModelParams interface
   copyInputs(array: Float64Array | undefined, create: (numElements: number) => Float64Array): void {
+    if (this.inputs.lengthInElements === 0) {
+      // Note that the inputs section will be empty if the inputs parameter is empty,
+      // so we can skip copying in this case
+      return
+    }
+
     // Allocate (or reallocate) an array, if needed
     if (array === undefined || array.length < this.inputs.lengthInElements) {
       array = create(this.inputs.lengthInElements)
@@ -129,6 +135,8 @@ export class BufferedRunModelParams implements RunModelParams {
   // from RunModelParams interface
   copyOutputIndices(array: Int32Array | undefined, create: (numElements: number) => Int32Array): void {
     if (this.outputIndices.lengthInElements === 0) {
+      // Note that the output indices section can be empty if the output indices are
+      // not provided, so we can skip copying in this case
       return
     }
 

packages/runtime/src/runnable-model/referenced-run-model-params.spec.ts

@@ -87,6 +87,13 @@ describe('ReferencedRunModelParams', () => {
     array = new Float64Array([6, 6, 6, 6])
     params.copyInputs(array, create)
     expect(array).toEqual(new Float64Array([1, 2, 3, 6]))
+
+    // Verify case where params are updated with an empty inputs array.  Note that
+    // it is expected that the existing data is retained in the destination array;
+    // it is up to the calling code to clear or ignore that existing data.
+    params.updateFromParams([], outputs)
+    params.copyInputs(array, create)
+    expect(array).toEqual(new Float64Array([1, 2, 3, 6]))
   })
 
   it('should copy output indices', () => {

packages/runtime/src/wasm-model/_mocks/mock-wasm-module.ts

@@ -117,7 +117,15 @@ export class MockWasmModule implements WasmModule {
   _malloc(lengthInBytes: number): number {
     const currentOffset = this.mallocOffset
     this.allocs.set(currentOffset, lengthInBytes)
-    this.mallocOffset += lengthInBytes
+    if (lengthInBytes > 0) {
+      // Update the offset so that the next allocation starts after this one
+      this.mallocOffset += lengthInBytes
+    } else {
+      // In the case where the length is zero, add a little padding so that
+      // the next allocation is recorded at a different start address than
+      // this one
+      this.mallocOffset += 8
+    }
     return currentOffset
   }
 

packages/runtime/src/wasm-model/wasm-model.ts

@@ -141,7 +141,7 @@ class WasmModel implements RunnableModel {
     // Run the model
     const t0 = perfNow()
     this.wasmRunModel(
-      this.inputsBuffer.getAddress(),
+      this.inputsBuffer?.getAddress() || 0,
       this.outputsBuffer.getAddress(),
       outputIndicesBuffer?.getAddress() || 0
     )