Fold the repeated domain helpers into one copy each

src/domain/account/credentials.ts

@@ -17,6 +17,8 @@
  * NAME of the field they refused and never its value.
  */
 
+import { isRecord } from "../records"
+
 /** Session credentials. Main process only: these never cross IPC. */
 export type AccountSecrets = {
   sessionKey: string
@@ -66,10 +68,6 @@ export function accountFieldDiagnosis(error: unknown): string | undefined {
   return error instanceof AccountFieldError ? error.diagnosis : undefined
 }
 
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value)
-}
-
 /** A type-level description of a value: never the value, never its length. */
 function describeShape(value: unknown): string {
   if (value === undefined) return "undefined"

src/domain/account/modPaths.ts

@@ -30,6 +30,7 @@
 
 import { MODS_FOLDER_NAME } from "../mods/folder"
 import { normalizeFolderForComparison } from "../paths"
+import { isRecord } from "../records"
 
 /** Key of the section the mod folder list lives in. */
 const STRING_LIST_SETTINGS_SECTION = "stringListSettings"
@@ -61,10 +62,6 @@ export interface RepointModPathsResult {
   outcome: RepointModPathsOutcome
 }
 
-function asRecord(value: unknown): Record<string, unknown> | null {
-  return value && typeof value === "object" && !Array.isArray(value) ? (value as Record<string, unknown>) : null
-}
-
 /** True for a path the game wrote as an absolute one, on either platform. */
 function isAbsoluteEntry(entry: string): boolean {
   return /^([a-zA-Z]:[\\/]|[\\/])/.test(entry)
@@ -109,9 +106,10 @@ function defaultShapeAbsoluteEntry(value: unknown): string | null {
  * @param target The installation the game is about to be launched on.
  */
 export function repointModPaths(existingDocument: unknown, target: ModPathsTarget): RepointModPathsResult {
-  const document = asRecord(existingDocument)
-  const section = document && asRecord(document[STRING_LIST_SETTINGS_SECTION])
-  if (!document || !section || !(MOD_PATHS_KEY in section)) return { document: existingDocument, outcome: "unchanged" }
+  if (!isRecord(existingDocument)) return { document: existingDocument, outcome: "unchanged" }
+
+  const section = existingDocument[STRING_LIST_SETTINGS_SECTION]
+  if (!isRecord(section) || !(MOD_PATHS_KEY in section)) return { document: existingDocument, outcome: "unchanged" }
 
   const absolute = defaultShapeAbsoluteEntry(section[MOD_PATHS_KEY])
   if (absolute === null) return { document: existingDocument, outcome: "left-as-found" }
@@ -120,7 +118,7 @@ export function repointModPaths(existingDocument: unknown, target: ModPathsTarge
   const repointed = (section[MOD_PATHS_KEY] as string[]).map((entry) => (entry === absolute ? target.modsPath : entry))
 
   return {
-    document: { ...document, [STRING_LIST_SETTINGS_SECTION]: { ...section, [MOD_PATHS_KEY]: repointed } },
+    document: { ...existingDocument, [STRING_LIST_SETTINGS_SECTION]: { ...section, [MOD_PATHS_KEY]: repointed } },
     outcome: "repointed"
   }
 }

src/domain/appUpdate/canAutoUpdate.ts

@@ -11,6 +11,8 @@
  * marker stays refused. Nothing is published for macOS at all.
  */
 
+import { refuse } from "../refusal"
+
 /** Why the updater stays off. */
 export type CanAutoUpdateFailure = "updates-disabled" | "linux-unsupported-package" | "unsupported-platform"
 
@@ -26,10 +28,6 @@ export interface CanAutoUpdateInput {
 /** The package-type marker values electron-updater has a Linux updater for. */
 const SUPPORTED_LINUX_PACKAGE_TYPES: ReadonlySet<string> = new Set(["deb", "rpm", "pacman"])
 
-function refuse(reason: CanAutoUpdateFailure): CanAutoUpdateResult {
-  return { ok: false, reason }
-}
-
 /**
  * Says whether this run can check for, download and apply updates.
  *

src/domain/backgrounds.ts

@@ -16,6 +16,8 @@
  * the picker; unlike the full-size scene, it is rendered directly and never cached by the app.
  */
 
+import { isRecord } from "./records"
+
 /** The scene shipped inside the app. Selected when nothing else is, and the offline answer. */
 export const DEFAULT_BACKGROUND_ID = "default"
 
@@ -113,10 +115,6 @@ export function backgroundCacheFileName(id: string): string {
   return `${id}.jpg`
 }
 
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value)
-}
-
 function parseEntry(value: unknown): BackgroundType | null {
   if (!isRecord(value)) return null
   const { id, name, file, thumbnail, sha256 } = value

src/domain/config/migrations.ts

@@ -17,6 +17,8 @@
  * strange as it likes and the launcher still starts.
  */
 
+import { isRecord } from "../records"
+
 /** Schema every config the launcher writes today carries. */
 export const CURRENT_CONFIG_SCHEMA = 5
 
@@ -110,10 +112,6 @@ export interface ConfigMigrationOptions {
   readonly targetSchema?: number
 }
 
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value)
-}
-
 /**
  * Reads the schema a stored document is at.
  *

src/domain/installations/create.ts

@@ -1,5 +1,6 @@
 import type { IdGenerator } from "../ports"
 import { folderIsInUse } from "../paths"
+import { refuse } from "../refusal"
 
 /** Bounds an installation name must fall within. */
 export const INSTALLATION_NAME_MIN_LENGTH = 5
@@ -18,10 +19,6 @@ export interface InstallationFieldsInput {
   startParams: string
 }
 
-function refuseFields(reason: InstallationFieldsFailure): InstallationFieldsResult {
-  return { ok: false, reason }
-}
-
 /**
  * Checks the two rules that apply to an installation's data whether it is
  * being created or edited: the name has to fit inside the launcher's bounds,
@@ -33,8 +30,8 @@ function refuseFields(reason: InstallationFieldsFailure): InstallationFieldsResu
 export function validateInstallationFields(input: InstallationFieldsInput): InstallationFieldsResult {
   const { name, startParams } = input
 
-  if (name.length < INSTALLATION_NAME_MIN_LENGTH || name.length > INSTALLATION_NAME_MAX_LENGTH) return refuseFields("name-length")
-  if (startParams.includes(RESERVED_START_PARAM)) return refuseFields("reserved-start-param")
+  if (name.length < INSTALLATION_NAME_MIN_LENGTH || name.length > INSTALLATION_NAME_MAX_LENGTH) return refuse("name-length")
+  if (startParams.includes(RESERVED_START_PARAM)) return refuse("reserved-start-param")
 
   return { ok: true }
 }
@@ -87,10 +84,6 @@ export interface CreatedInstallation {
   totalTimePlayed: number
 }
 
-function refuseCreate(reason: CreateInstallationFailure): CreateInstallationResult {
-  return { ok: false, reason }
-}
-
 /**
  * Validates a new installation's fields and builds the record for it.
  *
@@ -103,9 +96,9 @@ function refuseCreate(reason: CreateInstallationFailure): CreateInstallationResu
  */
 export function createInstallation(ports: CreateInstallationPorts, input: CreateInstallationInput): CreateInstallationResult {
   const fields = validateInstallationFields(input)
-  if (!fields.ok) return refuseCreate(fields.reason)
+  if (!fields.ok) return refuse(fields.reason)
 
-  if (folderIsInUse(input.path, input.foldersInUse, input.platform)) return refuseCreate("folder-in-use")
+  if (folderIsInUse(input.path, input.foldersInUse, input.platform)) return refuse("folder-in-use")
 
   return {
     ok: true,

src/domain/installations/delete.ts

@@ -1,4 +1,5 @@
 import type { FileSystem } from "../ports"
+import { refuse } from "../refusal"
 import type { BackupRecord } from "./backup"
 import { deleteInstallationBackup } from "./backupDeletion"
 
@@ -45,10 +46,6 @@ export interface DeleteInstallationEvents {
   onBackupDeleteFailed?(path: string): void
 }
 
-function refuse(reason: DeleteInstallationFailure): DeleteInstallationResult {
-  return { ok: false, reason }
-}
-
 /**
  * Drops an installation's data off disk, optionally.
  *

src/domain/moddbVisibility.ts

@@ -28,6 +28,8 @@
  *    the first launches of a beta routinely land before it.
  */
 
+import { isRecord } from "./records"
+
 /** The launcher's own entry on the ModDB. */
 export const MODDB_LISTING_MOD_ID = 11016
 
@@ -150,10 +152,6 @@ export function moddbListingVersion(version: string): string {
 const LEGACY_ANSWERED = new Set(["accepted", "declined", "already-done"])
 const LEGACY_ACCEPTED = "accepted"
 
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value)
-}
-
 function readVersion(value: unknown): string {
   return typeof value === "string" && value.length > 0 && value.length <= MAX_VERSION_LENGTH ? value : ""
 }

src/domain/mods/install.ts

@@ -1,4 +1,5 @@
 import type { DownloadOutcome, Downloader, FileSystem, PathBuilder } from "../ports"
+import { refuse } from "../refusal"
 import { modsFolder } from "./folder"
 import { MOD_DISABLED_SUFFIX } from "./scanInstalled"
 
@@ -101,10 +102,6 @@ export function modArchiveFileName(release: ModReleaseToInstall, disabled = fals
   return `${release.modidstr}-${release.modversion}${MOD_ARCHIVE_EXTENSION}${disabled ? MOD_DISABLED_SUFFIX : ""}`
 }
 
-function refuse(reason: InstallModFailure): InstallModResult {
-  return { ok: false, reason }
-}
-
 /**
  * Puts one mod release in an installation's Mods folder, replacing the copy already there.
  *

src/domain/mods/moddb.ts

@@ -21,6 +21,8 @@
  * both shapes for the same field, not just an object.
  */
 
+import { isRecord } from "../records"
+
 /** Why a v1 response could not be trusted. */
 export type ModDbApiFailure = "api-error" | "malformed-response"
 
@@ -35,10 +37,6 @@ export type ModDbResponse<T> = { ok: true; payload: T } | { ok: false; reason: M
 /** The string v1 uses to mean success. Every other value, including a missing field, is a failure. */
 const SUCCESS_STATUS_CODE = "200"
 
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value)
-}
-
 /** True for a value the ModDB would consider filled in: a non-blank string, or anything else defined. */
 function present(value: unknown): boolean {
   return typeof value === "string" ? value.trim().length > 0 : value !== undefined && value !== null

src/domain/mods/profiles.ts

@@ -1,3 +1,4 @@
+import { isRecord } from "../records"
 import { MAX_MOD_ARCHIVES, renameModArchiveTo } from "./scanInstalled"
 
 /**
@@ -72,10 +73,6 @@ export function emptyModProfilesDocument(): ModProfilesDocument {
   return { format: MOD_PROFILES_FORMAT, activeProfileId: null, profiles: [] }
 }
 
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value)
-}
-
 /**
  * The last segment of a path, split on either separator: the renderer never has Node's path module,
  * and a Windows path reaches it with backslashes.

src/domain/optimum/manifest.ts

@@ -22,6 +22,8 @@
 
 import semver from "semver"
 
+import { isRecord } from "../records"
+
 /** The platforms an overlay is published for. A label on the wire, a closed set here. */
 export const OPTIMUM_RIDS = ["linux-x64", "win-x64"] as const
 
@@ -78,10 +80,6 @@ export interface OptimumManifest {
   files: OptimumFile[]
 }
 
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value)
-}
-
 /** The bare hex of a `sha256:`-prefixed field, or undefined when it is not one. */
 function readHash(value: unknown): string | undefined {
   if (typeof value !== "string") return undefined

src/domain/optimum/ndjson.ts

@@ -13,6 +13,8 @@
  * out of a closed set and a number between 0 and 99.
  */
 
+import { isRecord } from "../records"
+
 /**
  * Why a run did not succeed.
  *
@@ -75,10 +77,6 @@ export interface OptimumOutputReader {
   finish(): OptimumRunResult
 }
 
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value)
-}
-
 /**
  * Reads the reason off a failed result.
  *

src/domain/ports.ts

@@ -6,6 +6,17 @@
  * this folder may reach for Electron, Node, React or the DOM.
  */
 
+/**
+ * How one attempt on a host port ended.
+ *
+ * Four ports answer with this shape and each restated it once (#484). They stay four ports: only
+ * the shape is shared, and every one of them keeps the name it already answered under.
+ */
+export interface HostOutcome {
+  ok: boolean
+  error?: string
+}
+
 /** Storage the host exposes to the domain. */
 export interface FileSystem {
   /** Resolves true when `path` points at something that exists. */
@@ -32,10 +43,7 @@ export interface CompressRequest {
 }
 
 /** How a compression attempt ended. */
-export interface CompressOutcome {
-  ok: boolean
-  error?: string
-}
+export type CompressOutcome = HostOutcome
 
 /** Produces archives. Progress reporting and task UI stay on the host side. */
 export interface Archiver {
@@ -57,10 +65,7 @@ export interface ExtractRequest {
 }
 
 /** How an extraction attempt ended. */
-export interface ExtractOutcome {
-  ok: boolean
-  error?: string
-}
+export type ExtractOutcome = HostOutcome
 
 /**
  * Unpacks archives. Kept apart from {@link Archiver} because no service does
@@ -86,11 +91,9 @@ export interface DownloadRequest {
 }
 
 /** How a download attempt ended. */
-export interface DownloadOutcome {
-  ok: boolean
+export interface DownloadOutcome extends HostOutcome {
   /** Where the file landed. Only meaningful when `ok` is true. */
   filePath?: string
-  error?: string
 }
 
 /** Fetches files. Progress reporting and task UI stay on the host side. */
@@ -112,10 +115,7 @@ export interface UnpackRequest {
 }
 
 /** How an unpacking attempt ended. */
-export interface UnpackOutcome {
-  ok: boolean
-  error?: string
-}
+export type UnpackOutcome = HostOutcome
 
 /**
  * The two ways a downloaded game build becomes an installed folder.

src/domain/records.ts

@@ -0,0 +1,12 @@
+/**
+ * The object guard the launcher narrows an unknown value with.
+ *
+ * Twelve modules each held a byte-identical private copy of it, and `account/modPaths.ts` a
+ * variant returning the record or null (#484). `src/domain/redaction.ts` sets the precedent and
+ * its header says why: a predicate duplicated so a pure module can keep its own copy is how two
+ * copies drift apart. `src/ipc/validation.ts` re-exports this one, so the host modules and the
+ * tests that import it from there keep doing so.
+ */
+export function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value)
+}

src/domain/refusal.ts

@@ -0,0 +1,13 @@
+/**
+ * The one way a domain flow says no.
+ *
+ * Six modules held their own three-line copy of it and `installations/create.ts` two (#484), each
+ * differing only in the failure union, which the type parameter carries instead. What comes back is
+ * the same `{ ok: false, reason }`, `ok` still the literal every result union discriminates on.
+ *
+ * A refusal that carries more than a reason keeps its own helper, because those extra fields are
+ * part of what the caller has to act on: see `installations/backup.ts` and `installations/restore.ts`.
+ */
+export function refuse<R>(reason: R): { ok: false; reason: R } {
+  return { ok: false, reason }
+}