[ivanvpetrov]

Closes #1613

Description

Enables "strict": true and fixes every compiler error it raised (697 across core, cli, igx-templates, ng-schematics, scripts and the specs).

Config

• strict: true is set in tsconfig.json, tsconfig-pack.json and packages/ng-schematics/tsconfig.json. The ng-schematics config previously enabled only noImplicitAny, noImplicitThis and strictNullChecks.
• New dev dependencies:
  • @types/through2@^2.0.41 in core
  • @types/resolve@^1.20.6 in cli
  • yarn.lock only adds these two packages. Neither appears in the emitted declarations, so they stay dev-only.
  • After pulling, run yarn install; without it the build fails with TS7016 for resolve and through2.

How errors were fixed

• Type-only changes wherever possible.
  • ! is used for properties assigned after construction (template metadata, prompt-session state, schematic options) and for values that can't be missing at runtime (for example, a name the user just picked from a list built from the same source).
  • catch variables are narrowed with as Error.
• Lookups now return honest types.
  • getTemplateById, getTemplateByName, getComponentByName, getFrameworkById, getFrameworkByName and getProjectLibraryByName return T | undefined.
  • getProject returns ProjectTemplate | null.
  • getProjectLibrary returns ProjectLibrary | null | undefined, which matches what it returned before.
  • Callers that already checked the result needed no change; the others assert, keep their existing guard, or (for upgrade) gained one. See below.
• Specs only gained type annotations, ! and casts. No existing assertion or test input changed.

Public type changes (@igniteui/cli-core declarations)

TypeScript consumers that compile with strictNullChecks may need to handle the new undefined / null results. Worth a line in the release notes when the next version is cut.

• Lookup return types, as listed above.
• ProjectLibrary interface: the matching lookup signatures.
• BaseTemplate.setExtraConfiguration: now takes { [key: string]: unknown } and returns void.
• Template.registerInProject: now returns void.
• ProjectConfig.validateProperty: now returns { message?: string, valid: boolean, value?: any }.
• ChangeRequest.node and TypeScriptAstTransformer.formatter are now optional.
• defaultDelimiters is now Required<TemplateDelimiters>.

Changes that touch runtime code. Each one either gives the same result as before or replaces a code path that would have crashed:

• generateConfig / registerInProject in the React, Web Components, jQuery and Angular base templates now default options to {}. Previously a missing options crashed on the first property access.
• JSX self-closing elements without attributes are now created with an empty attribute list instead of undefined (core AST transformer and ReactTypeScriptFileUpdate). Both print <Tag />.
• Four project templates that never assigned dependencies now initialize it to []. Only component templates' dependencies are ever read.
• Util.formatPackageJson: the sort reduce no longer relies on (a = b) && acc, which would have returned "" for an empty version string.
• cli.run(args) is typed string | string[] instead of args = null. Every caller passes arguments, and yargs' parseAsync requires them.
• list: the group map is an object instead of an array used as a map. It is only read through Object.keys, so the output is unchanged.
• upgrade (CLI) and upgrade-packages (ng-schematics): a framework and project type that don't match each other in ignite-ui-cli.json (e.g. angular with igc-ts) used to crash with Cannot read properties of undefined (reading 'projectIds'). They now report the existing "No valid Ignite UI project template found to upgrade packages." error. A spec covers each command.
• ng-schematics ng-new: the "folder exists" check now skips a missing name explicitly. It already returned false in that case.
• ng-schematics: the unused IgxSchematicContext interface was removed; its extra fields were never read. Rules now use SchematicContext.

Related Issue

Closes #1613

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring / code cleanup
• Build / CI configuration change

Affected Packages

• igniteui-cli (packages/cli)
• @igniteui/cli-core (packages/core)
• @igniteui/angular-templates (packages/igx-templates)
• @igniteui/angular-schematics (packages/ng-schematics)
• @igniteui/mcp-server (packages/igniteui-mcp)

Checklist

• I have tested my changes locally (npm run test)
• I have built the project successfully (npm run build)
• I have run the linter (npm run lint)
• I have added/updated tests as needed
• My changes do not introduce new warnings or errors

Additional Context

This is the last of three stacked PRs for #1613. It is based on #1850 (coverage), which is based on #1849 (bug fixes).

Verification

• tsc with tsconfig.json and with tsconfig-pack.json: 0 errors.
• npm run test: 767 specs pass (2 pending, unchanged).
• npm run lint: 0 errors; the one warning (unused eslint-disable in packages/core/util/Schematics.ts) is already on master.
• scripts/smoke-test.sh:
  • React and Web Components pass, including install and build.
  • All 220 ig add steps pass across the three frameworks.
  • The Angular project fails to install and build because of an unrelated upstream change. igniteui-angular@22.2.3, published 2026-10-19, is picked up by the templates' ~22.2.0. It needs igniteui-grid-lite@~0.11.0, while the grid-lite template pins ~0.10.0, and it rejects APIs the template payloads still use (igxButton="raised", actionStrip, IButtonGroupButton). This PR changes no template payloads (files/); a separate issue will cover it.

Notes for reviewers

• scripts/versionScript.ts changes by one character (let version!: string;), needed because scripts/ compiles under the root tsconfig.json.

Follow-ups, out of scope here

• packages/ng-schematics/tsconfig.json still reports 22 errors that predate this PR: 21 unused locals/parameters from its noUnused* options, and 1 esModuleInterop error in igx-templates/index.ts. CI doesn't build with this config.
• spec/helpers/utils.ts filesDiff() applies transform1 to the second list and globs folderPath1 twice. That is a bug in the test helper; it was left as is to keep test behaviour unchanged.
• cli.run still checks args ? yargs(args) : yargs, but since args is now required, the bare yargs branch can't be reached.

[coveralls]

Coverage is 95.369% — ipetrov/ts-strict-mode into ipetrov/igx-templates-coverage. No base build found for ipetrov/igx-templates-coverage.