GRASS GSoC 2025 Add JSON output to different tools in C

Student Name	Nishant Bansal
Organization	​OSGeo - Open Source Geospatial Foundation
Mentor Name	Anna Petrasova, Corey White, Vaclav Petras
GitHub Fork	View Repo
GSoC proposal	View Proposal

Abstract

Currently, most GRASS tools produce data in plain text by default. This means that users who want to process the output in Python need to create custom parsing code. To make this easier, several modules could be improved by offering JSON as an alternative output format. Recently, the Parson library was added to the GRASS codebase to support JSON output in addition to plain text. Building on the advancements made during the last GSoC, my project aims to expand JSON output capabilities to more tools using the Parson library.

Goal

1. Working with mentors to finalize the structure of the JSON output.
2. Adding an option to choose the output format (plain text or JSON) for each updated tool.
3. Developing Python test cases to ensure that the JSON output works correctly and to avoid future issues.
4. Providing basic documentation and example JSON outputs for each modified tool.
5. Develop simple examples demonstrating how to use JSON output in a data science workflow, such as reading JSON data into pandas or python.

Timeline

Period	Timeline	Tasks	Status
Bonding Period	May 8 - June 1	Reviewed the work done during the last GSoC to stabilize the JSON output. Discussed the priority tools for adding JSON support. Read GRASS documentation to add Python and JSON examples to the documentation.	OK OK OK
Official Coding Period
	Week 1 (June 2 - June 8)	Add JSON support for g.mapset #5810 Fix uninitialized zone_value in r.univar #5821 Add JSON support for r.what.color #5822 Update test file in r.info #5842 Improve interface for r.info #5859	OK OK OK OK OK
	Week 2 (June 9 - June 15)	Add JSON support for g.version #5863 Add JSON support for i.group #5870 Add test file in r.stats #5879 Add tests for JSON output in r.stats #5892	OK OK OK OK
	Week 3 (June 16 - June 22)	Update the JSON output schema of v.distance #5898 Fix uninitialized window variable in r.stats #5900 Add test file in g.list #5906 Add JSON support for g.list #5921 Update the JSON output schema of g.region #5929	OK OK OK OK OK
	Week 4 (June 23 - June 29)	Update the JSON output schema of v.to.db #5946 Update the JSON output schema of r.profile #5962 Add SHELL and CSV output support for r.univar #5966	OK OK OK
	Week 5 (June 30 - July 6)	Add test file in r.regression.line #5990 Add JSON support for r.regression.line #5993 Add test file in r.stats.quantile #6002 Add JSON support for r.stats.quantile #6007 Add test file in r.volume #6027 Add JSON support for r.volume #6036	OK OK OK OK OK OK
	Week 6 (July 7 - July 13)	Add JSON support for db.columns #6042 Add test file in m.measure #6051 Add test file in db.connect #6052 Add JSON support for m.measure #6053	OK OK OK OK
	Week 7 (July 14 - July 20)
	Week 8 (July 21 - July 27)
	Week 9 (July 28 - August 3)
	Week 10 (August 4 - August 10)
	Week 11 (August 11 - August 17)
	Week 12 (August 18 - August 24)
Evaluation Period
	August 25 - September 1

Reports

Community Bonding Period

What did I get done this week?

• Introduced myself on the OSGeo Discourse mailing list.
• Created both my personal Wiki page and the project Wiki page, adding all necessary project-related information.
• Read GRASS documentation to support the addition of Python and JSON examples.
• Worked on the following pull requests:
  • #5688
  • #5773
  • #5775
  • #5784
  • #5785

What do I plan on doing next week?

• Add JSON output support to the g.mapset and r.what.color modules.
• If time permits, I will begin improving the r.info interface: Issue #5793

Am I blocked on anything?

• No, I am not currently blocked on anything.

Project Discussions and Meetings

• 14 May 2025: Introductory meeting discussing JSON support and overall project milestones.
• 21 May 2025: Introduction with fellow developers. Discussed priority tools, adding Python/Pandas examples, and approaches for finalizing the JSON schema for each module.

Week-1

What did I get done this week?

• g.mapset: Added JSON output support, now you can use -p and -l flags to get JSON-formatted results.
• r.univar: Fixed a bug causing an uninitialized zone_value.
• r.what.color: Implemented JSON output support. (See PR #5822)
• r.info (regression tests): To maintain backward compatibility while updating its interface, I added strong regression tests.
• r.info (interface improvements): Began improving the module’s interface. (See PR #5859)

What do I plan on doing next week?

• Address review comments on my open PRs.
• Add JSON output support to g.version (see issue #5816).
• Add JSON output support to i.group (see issue #5815).
• If time permits, write tests for r.stats (see issue #5814).

Am I blocked on anything?

• No, I am not currently blocked on anything.

Week-2

What did I get done this week?

• g.version: Implemented JSON output support. (See PR #5863)
• i.group: Implemented JSON output support. (See PR #5870)
• r.stats (regression tests): To maintain backward compatibility while adding JSON format, I added strong regression tests.
• r.stats: Added tests for JSON output; this uncovered a bug, which was fixed alongside.

What do I plan on doing next week?

• Address review comments on my open PRs.
• Update JSON output format of v.distance (see issue #5846).
• Add JSON output support to g.list (see issue #5848).
• If time permits, fix the JSON output format of g.region (see issue #5828).

Am I blocked on anything?

• No, I am not currently blocked on anything.

Week-3

What did I get done this week?

• v.distance: Updated the JSON output schema. (See PR #5898)
• r.stats: Fixed a bug causing an uninitialized window variable.
• g.list (regression tests): To maintain backward compatibility while adding JSON format, I added strong regression tests.
• g.list: Implemented JSON output support. (See PR #5921)
• g.region: Updated the JSON output schema. (See PR #5929)

What do I plan on doing next week?

• Address review comments on my open PRs.
• Update JSON output format of v.to.db (see issue #5711).
• Update JSON output format and documentation of r.profile (see issue #5834).
• If time permits, add shell and csv output formats to r.univar (see issue #5824).

Am I blocked on anything?

• No, I am not currently blocked on anything.

Week-4

What did I get done this week?

• v.to.db: Updated the JSON output schema. (See PR #5946)
• r.profile: Updated the JSON output schema. (See PR #5962)
• r.univar: Implemented SHELL and CSV output support. (See PR #5966)

What do I plan on doing next week?

• Add JSON output support to r.regression.line (see issue #5950).
• Add JSON output support to r.stats.quantile (see issue #5951).
• Add JSON output support to r.volume (see issue #5949).

Am I blocked on anything?

• No, I am not currently blocked on anything.

Week-5

What did I get done this week?

• r.regression.line (regression tests): To maintain backward compatibility while adding JSON format, I added strong regression tests.
• r.regression.line: Implemented JSON output support. (See PR #5993)
• r.stats.quantile (regression tests): To maintain backward compatibility while adding JSON format, I added strong regression tests.
• r.stats.quantile: Implemented JSON output support. (See PR #6007)
• r.volume (regression tests): To maintain backward compatibility while adding JSON format, I added strong regression tests.
• r.volume: Implemented JSON output support. (See PR #6036)

What do I plan on doing next week?

• Add JSON output support to m.measure (see issue #6006).
• Add JSON output support to db.columns (see issue #6008).
• Add JSON output support to db.connect (see issue #6009).

Am I blocked on anything?

• No, I am not currently blocked on anything.

Week-6

What did I get done this week?

• db.columns: Implemented JSON output support. (See PR #6042)
• m.measure (regression tests): To maintain backward compatibility while adding JSON format, I added strong regression tests.
• db.connect (regression tests): To maintain backward compatibility while adding JSON format, I added strong regression tests.
• m.measure: Implemented JSON output support. (See PR #6053)

What do I plan on doing next week?

Am I blocked on anything?

• No, I am not currently blocked on anything.

Log of Pull Requests

Below is a list of pull requests submitted to the GRASS repository during GSoC 2025:

Pull Request	Description	Date	Status
#5688	r.univar: Fix JSON structure	May 20, 2025	Merged
#5773	r.what.color: Add test file	May 25, 2025	Merged
#5775	g.mapset: Add test file	May 26, 2025	Merged
#5784	r.info: Add Python example	May 28, 2025	Closed
#5785	g.region: Add Python example	May 28, 2025	Merged
#5810	g.mapset: Add JSON support	June 2, 2025	Merged
#5821	r.univar: Fix uninitialized zone_value	June 3, 2025	Merged
#5822	r.what.color: Add JSON support	June 3, 2025	Merged
#5842	r.info: Update test file	June 5, 2025	Merged
#5859	r.info: Improve interface	June 7, 2025	Merged
#5863	g.version: Add JSON support	June 9, 2025	Merged
#5870	i.group: Add JSON support	June 10, 2025	Merged
#5879	r.stats: Add test file	June 12, 2025	Merged
#5892	r.stats: Add tests for JSON output	June 14, 2025	Merged
#5898	v.distance: Update JSON format	June 16, 2025	Merged
#5900	r.stats: fix uninitialised window value	June 17, 2025	Merged
#5906	g.list: Add test file	June 17, 2025	Merged
#5921	g.list: Add JSON support	June 20, 2025	Merged
#5929	g.region: Update JSON format	June 21, 2025	Merged
#5946	v.to.db: Update JSON format	June 23, 2025	Merged
#5962	r.profile: Update JSON format	June 25, 2025	Merged
#5966	r.univar: Add shell and CSV format	June 25, 2025	Merged
#5990	r.regression.line: Add test file	June 30, 2025	Merged
#5993	r.regression.line: Add JSON support	June 30, 2025	Merged
#6002	r.stats.quantile: Add test file	July 1, 2025	Merged
#6007	r.stats.quantile: Add JSON support	July 1, 2025	Merged
#6027	r.volume: Add test file	July 4, 2025	Merged
#6036	r.volume: Add JSON support	July 6, 2025	Merged
#6042	db.columns: Add JSON support	July 7, 2025	Open
#6051	m.measure: Add test file	July 10, 2025	Merged
#6052	db.connect: Add test file	July 10, 2025	Open
#6053	m.measure: Add JSON support	July 11, 2025	Open