Show information gain in header validator output

ts/src/header-validator/context.ts

@@ -8,11 +8,16 @@ export type Issue = {
 export type ValidationResult = {
   errors: Issue[]
   warnings: Issue[]
+  notes: Issue[]
 }
 
 export class Context {
   private readonly path: PathComponent[] = []
-  private readonly result: ValidationResult = { errors: [], warnings: [] }
+  private readonly result: ValidationResult = {
+    errors: [],
+    warnings: [],
+    notes: [],
+  }
 
   scope<T>(c: PathComponent, f: () => T): T {
     this.path.push(c)
@@ -33,6 +38,10 @@ export class Context {
     this.result.warnings.push(this.issue(msg))
   }
 
+  note(msg: string): void {
+    this.result.notes.push(this.issue(msg))
+  }
+
   finish(topLevelError?: string): ValidationResult {
     if (typeof topLevelError !== 'undefined') {
       this.result.errors.push({ msg: topLevelError })

ts/src/header-validator/index.html

@@ -85,6 +85,8 @@ <h1>Attribution Reporting Header Validation</h1>
         <ul id=errors></ul>
         <p>Warnings:
         <ul id=warnings></ul>
+        <p>Notes:
+        <ul id=notes></ul>
       </output>
     </fieldset>
   </div>

ts/src/header-validator/index.ts

@@ -13,6 +13,7 @@ const sourceTypeRadios = form.elements.namedItem(
 )! as RadioNodeList
 const errorList = document.querySelector('#errors')!
 const warningList = document.querySelector('#warnings')!
+const noteList = document.querySelector('#note')!
 const successDiv = document.querySelector('#success')!
 const sourceTypeFieldset = document.querySelector(
   '#source-type'
@@ -69,7 +70,8 @@ function validate(): void {
         input.value,
         vsv.Chromium,
         sourceType(),
-        flexCheckbox.checked
+        flexCheckbox.checked,
+        /*noteInfoGain=*/true,
       )[0]
       break
     case 'trigger':
@@ -103,6 +105,7 @@ function validate(): void {
 
   errorList.replaceChildren(...result.errors.map(makeLi))
   warningList.replaceChildren(...result.warnings.map(makeLi))
+  noteList.replaceChildren(...result.notes.map(makeLi))
 }
 
 form.addEventListener('input', validate)

ts/src/header-validator/source.test.ts

@@ -11,6 +11,7 @@ import * as jsontest from './validate-json.test'
 
 type TestCase = jsontest.TestCase<Source> & {
   sourceType?: SourceType
+  noteInfoGain?: boolean
 }
 
 const testCases: TestCase[] = [
@@ -1220,7 +1221,7 @@ const testCases: TestCase[] = [
   },
 
   {
-    name: 'channel-capacity-default-event',
+    name: 'channel-capacity-default-event-custom-max',
     json: `{"destination": "https://a.test"}`,
     sourceType: SourceType.event,
     vsv: {
@@ -1233,12 +1234,12 @@ const testCases: TestCase[] = [
     expectedErrors: [
       {
         path: [],
-        msg: 'exceeds max event-level channel capacity per event source (1.58 > 0.00)',
+        msg: 'exceeds max event-level channel capacity per event source (1.585 > 0.000)',
       },
     ],
   },
   {
-    name: 'channel-capacity-default-navigation',
+    name: 'channel-capacity-default-navigation-custom-max',
     json: `{"destination": "https://a.test"}`,
     sourceType: SourceType.navigation,
     vsv: {
@@ -1251,7 +1252,53 @@ const testCases: TestCase[] = [
     expectedErrors: [
       {
         path: [],
-        msg: 'exceeds max event-level channel capacity per navigation source (11.46 > 0.00)',
+        msg: 'exceeds max event-level channel capacity per navigation source (11.462 > 0.000)',
+      },
+    ],
+  },
+  {
+    name: 'channel-capacity-default-event-notes',
+    json: `{"destination": "https://a.test"}`,
+    sourceType: SourceType.event,
+    noteInfoGain: true,
+    vsv: {
+      maxSettableEventLevelEpsilon: 14,
+    },
+    expectedNotes: [
+      {
+        path: [],
+        msg: 'number of possible output states: 3',
+      },
+      {
+        path: [],
+        msg: 'information gain: 1.585',
+      },
+      {
+        path: [],
+        msg: 'randomized response rate: 0.00025%',
+      },
+    ],
+  },
+  {
+    name: 'channel-capacity-default-navigation-notes',
+    json: `{"destination": "https://a.test"}`,
+    sourceType: SourceType.navigation,
+    noteInfoGain: true,
+    vsv: {
+      maxSettableEventLevelEpsilon: 14,
+    },
+    expectedNotes: [
+      {
+        path: [],
+        msg: 'number of possible output states: 2925',
+      },
+      {
+        path: [],
+        msg: 'information gain: 11.462',
+      },
+      {
+        path: [],
+        msg: 'randomized response rate: 0.24263%',
       },
     ],
   },
@@ -1833,7 +1880,8 @@ testCases.forEach((tc) =>
       tc.json,
       { ...vsv.Chromium, ...tc.vsv },
       tc.sourceType ?? SourceType.navigation,
-      tc.parseFullFlex ?? false
+      tc.parseFullFlex ?? false,
+      tc.noteInfoGain ?? false
     )
   )
 )

ts/src/header-validator/util.test.ts

@@ -5,6 +5,7 @@ import * as context from './context'
 export type TestCase = {
   expectedWarnings?: context.Issue[]
   expectedErrors?: context.Issue[]
+  expectedNotes?: context.Issue[]
 }
 
 export function run(
@@ -17,6 +18,7 @@ export function run(
     assert.deepEqual(result, {
       errors: tc.expectedErrors ?? [],
       warnings: tc.expectedWarnings ?? [],
+      notes: tc.expectedNotes ?? [],
     })
   })
 }

ts/src/header-validator/validate-json.ts

@@ -30,7 +30,8 @@ class SourceContext extends RegistrationContext {
   constructor(
     vsv: Readonly<VendorSpecificValues>,
     parseFullFlex: boolean,
-    readonly sourceType: SourceType
+    readonly sourceType: SourceType,
+    readonly noteInfoGain: boolean
   ) {
     super(vsv, parseFullFlex)
   }
@@ -832,18 +833,22 @@ function channelCapacity(ctx: SourceContext, s: Source): void {
     perTriggerDataConfigs
   )
 
-  const { infoGain } = config.computeConfigData(
+  const out = config.computeConfigData(
     s.eventLevelEpsilon,
     ctx.vsv.maxEventLevelChannelCapacityPerSource[ctx.sourceType]
   )
 
   const max = ctx.vsv.maxEventLevelChannelCapacityPerSource[ctx.sourceType]
-  if (infoGain > max) {
+  if (out.infoGain > max) {
     ctx.error(
       `exceeds max event-level channel capacity per ${
         ctx.sourceType
-      } source (${infoGain.toFixed(2)} > ${max.toFixed(2)})`
+      } source (${out.infoGain.toFixed(3)} > ${max.toFixed(3)})`
     )
+  } else if (ctx.noteInfoGain) {
+    ctx.note(`number of possible output states: ${out.numStates}`)
+    ctx.note(`information gain: ${out.infoGain.toFixed(3)}`)
+    ctx.note(`randomized response rate: ${(100 * out.flipProb).toFixed(5)}%`)
   }
 }
 
@@ -1421,10 +1426,11 @@ export function validateSource(
   json: string,
   vsv: Readonly<VendorSpecificValues>,
   sourceType: SourceType,
-  parseFullFlex: boolean = false
+  parseFullFlex: boolean = false,
+  noteInfoGain: boolean = false
 ): [ValidationResult, Maybe<Source>] {
   return validateJSON(
-    new SourceContext(vsv, parseFullFlex, sourceType),
+    new SourceContext(vsv, parseFullFlex, sourceType, noteInfoGain),
     json,
     source
   )