Migrate to ESLint 9 with flat config

[Copilot]

ESLint 8 to ESLint 9 Migration - Complete ✅

This PR successfully migrates the repository from ESLint 8 to ESLint 9 with flat config format.

Summary of Changes

• Updated @talend/eslint-config package to support ESLint 9

  • Updated dependencies to ESLint 9.39.2 and TypeScript ESLint 8.x
  • Created new eslint.config.js using flat config format
  • Migrated all rules from .eslintrc.json to flat config
  • Maintained automatic TypeScript detection
  • Kept index.js as main entry point for compatibility
  • Simplified dependencies (removed unused plugins)

• Removed lint command from @talend/scripts-core

  • Removed from help documentation
  • Added deprecation message with migration guidance
  • Fixed all exit codes to use standard exit(1)

• Updated all package lint scripts (36 packages)

  • Replaced "talend-scripts lint" with "eslint ."
  • Restored specific file patterns for packages that had custom paths
  • Standardized all variations to "eslint ."
  • Fixed JSON syntax errors

• Added ESLint 9 configs to all packages

  • Created eslint.config.js in 51 packages
  • All configs reference @talend/eslint-config
  • Added root-level eslint.config.js

• Updated documentation

  • Comprehensive README with migration guide
  • Usage examples and customization instructions
  • IDE configuration (VS Code)
  • Breaking changes documentation

• Code review and security

  • Addressed all code review feedback
  • Fixed ignore patterns to be more specific
  • Security scan passed (0 vulnerabilities)
  • Restored original file patterns for custom lint paths

Breaking Changes

• Requires ESLint 9.x (was 8.x)
• Uses flat config format instead of .eslintrc format
• talend-scripts lint command removed - use eslint . directly
• Updated plugin dependencies to ESLint 9 compatible versions

Testing Notes

• All packages now use direct ESLint 9 invocation
• Configuration dynamically detects TypeScript projects
• Compatible with existing .eslintrc.json files during transition
• Root workspace lint command unchanged: yarn lint
• Packages with specific file patterns maintain their original paths

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Migrate to eslint 9</issue_title>
<issue_description>Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

We are using a dead eslint 8

Describe the solution you'd like
A clear and concise description of what you want to happen.

• update scripts-config-eslint to be ready to be used with eslint 9 as a config file
• remove talend-scripts lint command
• replace in each packages the lint script from talend-scripts to eslint 9 using the scripts-config-eslint package.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Migrate to eslint 9 #5689

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[changeset-bot]

⚠️ No Changeset found

Latest commit: 133d84a

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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[github-actions]

Storybook for this PR deployed on this github page

[github-actions]

Title	Lines	Statements	Branches	Functions
assets-api		28.4% (25/88)	30.76% (16/52)	21.42% (3/14)
cmf		89.36% (1243/1391)	80.93% (607/750)	89.51% (350/391)
cmf-cqrs		87.43% (160/183)	70.23% (59/84)	84.21% (48/57)
cmf-router		69.23% (135/195)	55.71% (78/140)	56.81% (25/44)
components		90.7% (5565/6135)	81.59% (3196/3917)	88.14% (1390/1577)
containers		83.6% (1392/1665)	74.3% (694/934)	75% (327/436)
dataviz		85.44% (323/378)	66.66% (160/240)	75.79% (119/157)
design-system		66.49% (1016/1528)	50.84% (543/1068)	53.94% (219/406)
faceted-search		85.08% (639/751)	78.63% (287/365)	81.88% (226/276)
flow-designer		70.07% (651/929)	66.72% (355/532)	70.92% (200/282)
forms		86.27% (1640/1901)	75.89% (929/1224)	85.02% (460/541)
http		100% (85/85)	98.07% (51/52)	100% (34/34)
sagas		92.3% (24/26)	66.66% (4/6)	50% (2/4)
stepper		81.52% (150/184)	59.34% (54/91)	80.85% (38/47)
utils		100% (73/73)	90.9% (10/11)	100% (24/24)

[jmfrancois]

@copilot can you lint only the same files as before please ?

[Copilot]

Done. Restored the original file patterns for packages that had specific paths:

• faceted-search-query-client: eslint ./src/**/*.js ./stories/**/*.js ./.storybook/**/*.js
• faceted-search: eslint ./src/**/*.js ./stories/**/*.js ./.storybook/**/*.js
• local-libs-webpack-plugin: eslint lib/**/*.js

These now lint only the same files as before. (commit 32445e7)