CLI: add stdin support for instance validation by Vaibhav701161 · Pull Request #614 · sourcemeta/jsonschema

Vaibhav701161 · 2026-01-15T09:35:35Z

Adds stdin support for instance input to enable real-time editor diagnostics.
Fixes(#537)

Centralized stdin parsing in src/input.h (JSON-first, YAML fallback).
validate accepts instances from stdin only; schemas must be file paths.
Stdin inputs resolve relative $ref against the current working directory.
Includes integration test test/validate/pass_stdin.sh.
Unblocks sourcemeta/studio#61; addresses sourcemeta/jsonschema#537.

Refs: sourcemeta/studio#61, #537

*Build and test:

Vaibhav701161 · 2026-01-17T05:37:30Z

Hi @jviotti , I’ve opened this PR and would appreciate a review when you have time. Thanks!

jviotti · 2026-01-19T12:37:22Z

Hey @Vaibhav701161 , sorry for the delay. It has been a hectic week. I'll try to get into it today

jviotti · 2026-01-19T12:54:42Z

I like the idea but I think there are some things to iron out:

If we accept standard input, we should do so in ALL commands, otherwise it gets weird
Some commands require a schema as input but for others, passing nothing means "the current directory", which introduces some ambiguity. For example, jsonschema fmt formats all schemas in the current directory, while jsonschema inspect <schema.json> requires a single schema argument
Furthermore, some commands require 2 schemas, like validate

I think for consistency, we can require the - to signify standard input in every command. However, for commands take potentially take directories as input, we should transparently implement this logic on src/input.h. So it happens out of the box.

The other problem here will be line numbers. We should make sure all relevant commands handle standard input while still reporting line/column information and potentially some "special" file path like <stdin>?

Vaibhav701161 · 2026-01-20T04:03:35Z

Hey @jviotti , thanks a lot for the feedback.

I’ve pushed an updated iteration that tries to address the concerns you mentioned:

- is now the explicit opt-in for stdin.
The stdin logic is centralized in src/input.h, so it’s not handled ad-hoc in individual commands.
Ambiguous cases (schema via stdin, multiple stdin inputs) are explicitly rejected.
Line/column information is preserved, and stdin is handled as a special input (covered via tests).

Vaibhav701161 · 2026-02-01T13:45:46Z

Hi @jviotti , just a quick follow-up on this.
Whenever you get a chance, I’d appreciate a review to confirm whether this direction looks good or if there’s anything you’d like adjusted before moving forward. Thanks

src/input.h

jviotti · 2026-01-21T13:22:33Z

src/input.h


 struct InputJSON {
  std::filesystem::path first;
+  std::filesystem::path resolution_base;


If this is just a display name, maybe make a std::string? Otherwise <stdin> is not really a path

I think this still needs to be addressed?

jviotti · 2026-01-21T13:23:20Z

test/validate/pass_stdin.sh

Please split this test into multiple tests. If you see the other tests in the project, we have specific conventions and we always test a single thing per file. Plus you also want to add test for every other applicable command.

Finally, you didn't register this test in test/CMakeLists.txt, so it won't run at all

jviotti · 2026-02-05T18:31:10Z

src/command_lint.cc

                  copy, sourcemeta::core::schema_walker, custom_resolver,
                  get_lint_callback(errors_array, entry, output_json), dialect,
-                  sourcemeta::jsonschema::default_id(entry.first),
+                  sourcemeta::core::URI::from_path(entry.resolution_base)


I think we still definitely want to use sourcemeta::jsonschema::default_id here, to concentrate that logic in a single place. Maybe make such function take entry directly, so that inside we can decide to use entry.resolution_base or whatever?

jviotti · 2026-02-05T18:31:16Z

src/command_lint.cc

                  custom_resolver,
                  get_lint_callback(errors_array, entry, output_json), dialect,
-                  sourcemeta::jsonschema::default_id(entry.first),
+                  sourcemeta::core::URI::from_path(entry.resolution_base)


jviotti · 2026-02-05T18:33:27Z

src/input.h

        // TODO: Print a verbose message for what is getting parsed
        auto parsed{read_file(canonical)};
-        result.push_back({std::move(canonical), std::move(parsed.document),
+        auto canonical_copy{canonical};


jviotti · 2026-02-05T18:33:37Z

src/input.h

    }
  }
 }
-


I don't think this deletion was intended?

jviotti · 2026-02-05T18:34:43Z

src/input.h

+    }
+  }
+  if (stdin_count > 1) {
+    throw std::runtime_error{"Standard input (-) can only be specified once"};


Suggested change

throw std::runtime_error{"Standard input (-) can only be specified once"};

throw std::runtime_error{"The standard input position argument `-` can only be specified once"};

jviotti · 2026-02-05T18:35:17Z

src/input.h

+  std::size_t stdin_count{0};
+  for (const auto &arg : arguments) {
+    if (arg == "-") {
+      stdin_count++;


I don't think counting all occurrences makes sense if you only want up to two. Maybe check that if you already got at least 2, then its an error and you can break?

jviotti · 2026-02-05T18:36:57Z

test/validate/pass_stdin.sh

+set +o errexit
+cat "$TMP/schema.json" > "$TMP/schema_stdin.json"
+
+OUTPUT=$("$1" validate - "$TMP/schema.json" < "$TMP/schema_stdin.json" 2>&1)


Please see the other shell scripts for the conventions on how we test stuff. Some obvious ones:

We never capture into a variable. We pipe into a file and then diff it

We never enable set +o errexit

We never test more than one thing at once

Also your test is not registered in test/CMakeLists.txt so it won't run at all. But overall, split it so that there are multiple tests testing each one thing

Signed-off-by: Vaibhav mittal <vaibhavmittal929@gmail.com>

cubic-dev-ai

4 issues found across 12 files

Prompt for AI agents (all issues)


Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="src/command_fmt.cc">

<violation number="1" location="src/command_fmt.cc:25">
P2: Use a structured error type from `error.h` instead of `std::runtime_error` for stdin not supported. This enables proper machine-readable JSON output when `--json` is passed, following the pattern of other error types like `YAMLInputError`.

(Based on your team's feedback about avoiding dynamically constructed exception messages and reusing centralized error wrapper types.) [FEEDBACK_USED]</violation>
</file>

<file name="src/input.h">

<violation number="1" location="src/input.h:151">
P2: Missing YAML fallback for stdin input. The PR description states "JSON-first, YAML fallback" but `read_from_stdin()` only parses JSON. This is inconsistent with file handling which falls back to YAML if JSON parsing fails. Note: implementing YAML fallback would require first buffering stdin (since it can only be read once), then attempting JSON parse, then falling back to YAML on failure.</violation>
</file>

<file name="test/validate/fail_stdin_multiple.sh">

<violation number="1" location="test/validate/fail_stdin_multiple.sh:25">
P2: Add a JSON error assertion for this failure case so the structured error output is validated alongside the text output.

(Based on your team's feedback about adding JSON variants for failure test cases.) [FEEDBACK_USED]</violation>
</file>

<file name="test/validate/fail_stdin_schema.sh">

<violation number="1" location="test/validate/fail_stdin_schema.sh:22">
P2: Add a JSON error assertion for this fail_* test so structured error output remains covered.

(Based on your team's feedback about adding JSON variants for failure test cases.) [FEEDBACK_USED]</violation>
</file>

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src/command_fmt.cc

src/input.h

cubic-dev-ai · 2026-02-06T11:25:19Z

test/validate/fail_stdin_multiple.sh

+error: The standard input position argument `-` can only be specified once
+EOF
+
+diff "$TMP/stderr.txt" "$TMP/expected.txt"


P2: Add a JSON error assertion for this failure case so the structured error output is validated alongside the text output.

(Based on your team's feedback about adding JSON variants for failure test cases.)

View Feedback

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At test/validate/fail_stdin_multiple.sh, line 25: <comment>Add a JSON error assertion for this failure case so the structured error output is validated alongside the text output. (Based on your team's feedback about adding JSON variants for failure test cases.) </comment> <file context> @@ -0,0 +1,25 @@ +error: The standard input position argument `-` can only be specified once +EOF + +diff "$TMP/stderr.txt" "$TMP/expected.txt" </file context>

I will fix this.

@Vaibhav701161 This is a valid one. Needs fixing!

cubic-dev-ai · 2026-02-06T11:25:19Z

test/validate/fail_stdin_schema.sh

+error: Reading the schema from standard input is not supported
+EOF
+
+diff "$TMP/stderr.txt" "$TMP/expected.txt"


P2: Add a JSON error assertion for this fail_* test so structured error output remains covered.

(Based on your team's feedback about adding JSON variants for failure test cases.)

View Feedback

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At test/validate/fail_stdin_schema.sh, line 22: <comment>Add a JSON error assertion for this fail_* test so structured error output remains covered. (Based on your team's feedback about adding JSON variants for failure test cases.) </comment> <file context> @@ -0,0 +1,22 @@ +error: Reading the schema from standard input is not supported +EOF + +diff "$TMP/stderr.txt" "$TMP/expected.txt" </file context>

I will fix this.

jviotti · 2026-02-12T15:33:53Z

test/validate/pass_stdin_instance.sh

Can you add a failing case too?

jviotti · 2026-02-12T15:34:37Z

src/command_validate.cc


+  if (schema_path == "-") {
+    throw std::runtime_error{
+        "Reading the schema from standard input is not supported"};


Why not? Sounds like a valid use case, unless there is another reason why it wouldn't work that I'm not thinking about?

jviotti · 2026-02-12T15:35:20Z

test/CMakeLists.txt

So far we only have stdin tests for the validate command. But we should be testing stdin behaviour for every command that supports it. Otherwise it could be totally broken in other commands and we are not knowing about it

jviotti · 2026-02-12T15:35:34Z

src/command_fmt.cc

  for (const auto &entry : for_each_json(options)) {
+    if (entry.from_stdin) {
+      throw std::runtime_error{
+          "This command does not support reading from standard input"};


jviotti · 2026-02-12T15:36:09Z

I left some more comments. It's shaping up really well!

jviotti · 2026-02-12T15:39:26Z

@Vaibhav701161 The machinery that allows for - detection is already very solid. Something I suggest is sending another PR based on this one that does all the refactoring while not adding tests and not actually surfacing the - logic yet. That's legit refactoring that already looks great and we can merge, and then we can rebase this one with the changes and just focus on the - new logic.

I guess that would be most of the changes you made except the tests, and just never setting entry.from_stdin to true and never checking for two or more - so nothing is actually affected?

Vaibhav701161 force-pushed the feat/stdin-validate branch 2 times, most recently from ddb8312 to 9a040d7 Compare January 15, 2026 10:07

Vaibhav701161 force-pushed the feat/stdin-validate branch from 4d5ff3f to 112b374 Compare January 20, 2026 02:49

Vaibhav701161 force-pushed the feat/stdin-validate branch from f70d55d to b9bb23e Compare February 1, 2026 13:22

jviotti requested changes Feb 5, 2026

View reviewed changes

Vaibhav701161 added 6 commits February 6, 2026 05:51

Feat: support reading instances from stdin for validate and lint

8d9746f

Signed-off-by: Vaibhav mittal <vaibhavmittal929@gmail.com>

test: fix shellcheck SC2002 in stdin validation test

720f5df

Signed-off-by: Vaibhav mittal <vaibhavmittal929@gmail.com>

test: fix shellcheck SC2002 in stdin validation test-2

ebc4ea1

Signed-off-by: Vaibhav mittal <vaibhavmittal929@gmail.com>

feat:centralize stdin handling and add resolution context

44541cb

Signed-off-by: Vaibhav mittal <vaibhavmittal929@gmail.com>

test: cover stdin edge cases and fix shellcheck warnings

2e434c5

Signed-off-by: Vaibhav mittal <vaibhavmittal929@gmail.com>

test: cover stdin edge cases and fix shellcheck warnings-2

77066a9

Signed-off-by: Vaibhav mittal <vaibhavmittal929@gmail.com>

Vaibhav701161 force-pushed the feat/stdin-validate branch from b9bb23e to 77066a9 Compare February 6, 2026 06:17

feat(cli): support stdin for instances and formalize input resolution

16c70bc

Signed-off-by: Vaibhav mittal <vaibhavmittal929@gmail.com>

cubic-dev-ai bot reviewed Feb 6, 2026

View reviewed changes

Vaibhav701161 requested a review from jviotti February 6, 2026 11:57

jviotti reviewed Feb 12, 2026

View reviewed changes

test/validate/pass_stdin_instance.sh

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Can you add a failing case too?

jviotti reviewed Feb 12, 2026

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	throw std::runtime_error{"Standard input (-) can only be specified once"};
	throw std::runtime_error{"The standard input position argument `-` can only be specified once"};

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