Test json against schema only on demand

Testing json against schema requires an in-memory copy, so do it only
when requested by the test suite.

TODO

@@ -50,18 +50,6 @@ Output JSON v2
 
 Before starting on v2 format:
 
-* Some if not all of the json output functionality should move from
-  QPDFJob to QPDF. There can top-level QPDF methods that take a
-  pipeline and write the JSON serialization to it. For things that
-  generate smaller amounts of output (constant-size stuff, lists of
-  attachments), we can also have a version that returns a string. For
-  the benefit of users of other languages, we can have something that
-  takes a FILE* or writes to stdout as well. This would be a good time
-  to make sure all the information from --check and other
-  informational options (--show-linearization, --show-encryption,
-  --show-xref, --list-attachments, --show-npages) is available in the
-  json output.
-
 * Writing objects should write in numerical order with the trailer at
   the end.
 
@@ -70,15 +58,18 @@ Before starting on v2 format:
   the input), not by overwriting, in case this has any unwanted side
   effects.
 
-* Figure out how/whether to do schema checks with incremental write.
-  Consider changing the contract to allow fields to be absent even
-  when present in the schema. It's reasonable for people to check for
-  presence of a key. Most languages make this easy to do.
-
 General things to remember:
 
 * deprecate getJSON without a version
 
+* Make sure all the information from --check and other informational
+  options (--show-linearization, --show-encryption, --show-xref,
+  --list-attachments, --show-npages) is available in the json output.
+
+* Consider changing the contract to allow fields to be absent even
+  when present in the schema. It's reasonable for people to check for
+  presence of a key. Most languages make this easy to do.
+
 * The choices for json_key (job.yml) will be different for v1 and v2.
   That information is already duplicated in multiple places.
 

job.sums

@@ -14,4 +14,4 @@ libqpdf/qpdf/auto_job_json_decl.hh 06caa46eaf71db8a50c046f91866baa8087745a947431
 libqpdf/qpdf/auto_job_json_init.hh e7047a7c83737adfaae49abc295a579bb9b9e0a4644e911d1656a604cb202208
 libqpdf/qpdf/auto_job_schema.hh cbbcae166cfecbdbdeb40c5a30870e03604a019a8b4f7a217d554a82431d2e5f
 manual/_ext/qpdf.py 6add6321666031d55ed4aedf7c00e5662bba856dfcd66ccb526563bffefbb580
-manual/cli.rst 8a5a12351df6a42f91d6d271b2d065a843d8daa5125d8723d474e4180d7abbf1
+manual/cli.rst 8684ca1f601f2832cded52d1b2f74730f97b7b85b57e31a399231731fbe80d26

libqpdf/QPDFJob.cc

@@ -16,6 +16,7 @@
 #include <qpdf/Pl_Flate.hh>
 #include <qpdf/Pl_OStream.hh>
 #include <qpdf/Pl_StdioFile.hh>
+#include <qpdf/Pl_String.hh>
 #include <qpdf/QTC.hh>
 #include <qpdf/QUtil.hh>
 
@@ -1592,6 +1593,13 @@ QPDFJob::json_out_schema_v1()
 void
 QPDFJob::doJSON(QPDF& pdf, Pipeline* p)
 {
+    std::string captured_json;
+    std::shared_ptr<Pl_String> pl_str;
+    if (this->m->test_json_schema) {
+        pl_str = std::make_shared<Pl_String>("capture json", p, captured_json);
+        p = pl_str.get();
+    }
+
     JSON j = JSON::makeDictionary();
     // This version is updated every time a non-backward-compatible
     // change is made to the JSON format. Clients of the JSON are to
@@ -1651,23 +1659,22 @@ QPDFJob::doJSON(QPDF& pdf, Pipeline* p)
         doJSONObjectinfo(pdf, j);
     }
 
-    // Check against schema
+    *p << j.unparse() << "\n";
 
-    JSON schema = json_schema(&m->json_keys);
-    std::list<std::string> errors;
-    if (!j.checkSchema(schema, errors)) {
-        *(this->m->cerr)
-            << "QPDFJob didn't create JSON that complies with its own rules.\n\
-Please report this as a bug at\n\
-   https://github.com/qpdf/qpdf/issues/new\n\
-ideally with the file that caused the error and the output below. Thanks!\n\
-\n";
-        for (auto const& error: errors) {
-            *(this->m->cerr) << error << std::endl;
+    if (this->m->test_json_schema) {
+        // Check against schema
+        JSON schema = json_schema(&m->json_keys);
+        std::list<std::string> errors;
+        JSON captured = JSON::parse(captured_json);
+        if (!captured.checkSchema(schema, errors)) {
+            *(this->m->cerr) << "QPDFJob didn't create JSON that complies with"
+                                " its own rules."
+                             << std::endl;
+            for (auto const& error: errors) {
+                *(this->m->cerr) << error << std::endl;
+            }
         }
     }
-
-    *p << j.unparse() << "\n";
 }
 
 void

manual/cli.rst

@@ -3336,6 +3336,9 @@ Related Options
 
    This is used by qpdf's test suite to check consistency between the
    output of ``qpdf --json`` and the output of ``qpdf --json-help``.
+   This option causes an extra copy of the generated json to appear in
+   memory and is therefore unsuitable for use with large files. This
+   is why it's also not on by default.
 
 .. _unicode-passwords:
 

qpdf/qtest/qpdf.test

@@ -1124,7 +1124,8 @@ foreach my $d (@json_files)
     }
     my $in = "$file.pdf";
     $td->runtest("json $out",
-                 {$td->COMMAND => ['qpdf', '--json', @$xargs, $in]},
+                 {$td->COMMAND =>
+                      ['qpdf', '--json=1', '--test-json-schema', @$xargs, $in]},
                  {$td->FILE => "$out.out", $td->EXIT_STATUS => 0},
                  $td->NORMALIZE_NEWLINES);
 }