Add map-generator --maps flag to process a subset of maps

[Tidwell]

Resolves #2594

Description:

• Added an optional --maps flag to the map-generator that allows passing a subset of maps to process.
• Updated README.md w/ documentation for using the new flag

Used the go/flag package.

Running without the flag, or with no arguments matches existing behavior of processing all the maps defined in main.go

go run .
go run . --maps=

New behavior is triggered to process a subset of maps by passing the --maps flag. Multiple maps are defined in a comma-separated list

go run . --maps=world,africa

Or a single map (useful for map development)

go run . --maps=fourislands

If an invalid map is passed, the process aborts and renders the error

go run . --maps=invalidmapname
Error generating terrain maps: map "invalidmapname" is not defined
exit status 1

By using the default flag package, we get --help for free:

go run . --help
Usage of <path-to-exe>/exe/map-generator:
  -maps string
    	optional comma-separated list of maps to process. ex: --maps=world,eastasia,big_plains

I do not write GO often. Gemini contributed to this syntax.

Please complete the following:

• I have added screenshots for all UI updates
• I process any text displayed to the user through translateText() and I've added it to the en.json file
• I have added relevant tests to the test directory
• I confirm I have thoroughly tested these changes and take full responsibility for any bugs introduced

Please put your Discord username so you can be contacted if a bug or regression is found:

tidwell

[coderabbitai]

Walkthrough

The changes introduce a new optional --maps CLI flag to the map-generator, enabling selective processing of specific maps instead of processing all maps by default. Documentation is added explaining the feature and providing usage examples.

Changes

Cohort / File(s)	Summary
Documentation updates map-generator/README.md	Added documentation explaining default map processing behavior and how to use the --maps flag to target specific maps with single and comma-separated examples.
CLI flag and map selection map-generator/main.go	Introduced --maps optional CLI flag for selecting which maps to process. Added parseMapsFlag function to validate provided map names against available maps and return selected set. Integrated map selection into loadTerrainMaps to filter concurrent processing; updated main to parse flags and print success message.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• Flag parsing and validation logic is straightforward and follows a clear pattern
• Filtering integration into existing concurrent map processing is minimal
• Focus areas: Verify parseMapsFlag validation logic handles edge cases (empty input, invalid names, duplicates), and confirm map filtering in loadTerrainMaps maintains concurrent processing correctness

Possibly related PRs

• Fix uncompacted maps #2138 — Reorders the maps list in map-generator, which the new --maps flag validation logic depends on for determining available map names.

Suggested labels

Feature - Map

Suggested reviewers

• evanpelle

Poem

🗺️ A flag to choose your maps with care,
No need to comment lines everywhere,
Selective builds for dev so fast,
The workflow loop will truly last! ✨

Pre-merge checks

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding a --maps flag to the map-generator for processing specific maps.
Description check	✅ Passed	The description is detailed and directly related to the changeset, explaining the new flag functionality, usage examples, and how default behavior is preserved.
Linked Issues check	✅ Passed	The PR fully addresses issue #2594 by implementing the --maps CLI flag, supporting single/multiple maps, preserving default behavior, and enabling focused map development.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to the --maps flag feature: CLI flag parsing in main.go, validation logic, README documentation, and map selection integration.

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

map-generator/main.go (1)

169-187: Trim whitespace from map names for better user experience.

The validation logic is correct, but users might naturally type --maps=world, africa with spaces after commas. Currently this would fail with map " africa" is not defined. While debuggable, trimming whitespace is a common courtesy in CLI tools.

Apply this diff to handle whitespace gracefully:

 func parseMapsFlag() (map[string]bool, error) {
 	if mapsFlag == "" {
 		return nil, nil
 	}
 
 	validNames := make(map[string]bool, len(maps))
 	for _, m := range maps {
 		validNames[m.Name] = true
 	}
 
 	selected := make(map[string]bool)
 	for _, name := range strings.Split(mapsFlag, ",") {
+		name = strings.TrimSpace(name)
+		if name == "" {
+			continue
+		}
 		if !validNames[name] {
 			return nil, fmt.Errorf("map %q is not defined", name)
 		}
 		selected[name] = true
 	}
 	return selected, nil
 }

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 2bfe245 and 859ab4f.

📒 Files selected for processing (2)

• map-generator/README.md (1 hunks)
• map-generator/main.go (3 hunks)

🧰 Additional context used

🧠 Learnings (1)

📓 Common learnings

Learnt from: VariableVince
Repo: openfrontio/OpenFrontIO PR: 1655
File: resources/maps/giantworldmap/manifest.json:165-174
Timestamp: 2025-07-31T12:03:08.052Z
Learning: In OpenFrontIO draft PRs, flag names in map manifest files may be placeholders that will be updated to match the actual SVG flag file names when the assets are received. The final naming depends on the actual flag SVG files provided, not code naming conventions.

🔇 Additional comments (7)

map-generator/main.go (6)

5-5: LGTM!

The standard library imports are appropriate for the new CLI flag functionality.

Also applies to: 10-10

---

14-14: LGTM!

Package-level variable follows standard Go flag package conventions.

---

190-193: LGTM!

The flag parsing and validation is correctly integrated at the start of processing, with proper error propagation.

---

199-201: LGTM!

The filter logic correctly preserves backward compatibility (process all when flag is omitted) while enabling selective processing when the flag is provided.

---

203-203: LGTM!

The loop variable capture is correct and prevents a common Go concurrency issue where goroutines would all reference the same variable.

---

227-228: LGTM!

The flag definition is clear with a helpful usage example, and parsing happens at the correct point before map processing.

map-generator/README.md (1)

20-28: LGTM!

The documentation clearly explains the new flag functionality with helpful examples for both single-map and multi-map scenarios. The examples correctly show comma-separated format without spaces.

[evanpelle]

Thanks!