Charge a contract page for the values it maps, not the whole record per field

changelog.d/contract-projection-charge.md

@@ -0,0 +1,3 @@
+## Fixed
+
+- Count only the values a contract maps against a contract query's 1 MiB page budget. Each record's whole frontmatter was counted once per mapped field, so a page of 128 ordinary records (about 1.5 KB of frontmatter, 14 mapped fields) was refused with `too_large` / `contract_projection_budget`, and so was any single record over about 80 KB. Apps such as Writer could not load a Reader library of that shape.

docs/sdk-publication.md

@@ -83,7 +83,11 @@ updated; CI must not auto-bless its output. When updating pins, match the
 workflow's Rust path remapping as well as its pinned tools and optimizer flags:
 map the compiler host's checkout root to `/source` and Cargo home to `/cargo`.
 Source paths can survive WASM stripping, so builds without these mappings do not
-produce publication-compatible bytes. Verify the corrected pins with the actual
+produce publication-compatible bytes. A toolchain with the `rust-src`
+component embeds its own source path for the standard library where the
+workflow's minimal toolchain keeps `/rustc/<commit>`: map
+`~/.rustup/toolchains/<toolchain>/lib/rustlib/src/rust` to the `/rustc/<commit>`
+of `rustc -vV` as well, and check that the built WASM contains no `/home/` path. Verify the corrected pins with the actual
 `scripts/sdk-publication.mjs pack-all` cold-consumer and archive checks.
 After committing runtime changes and rebuilding `cargo xtask wasm-app` with
 those mappings, run `node scripts/sdk-publication.mjs pin-runtime` to regenerate

runtime/crates/replica/src/replica/client/contract_query.rs

@@ -10,6 +10,7 @@ use crate::{Store, convert};
 use mdbn_core::state::StateView;
 use mdbn_wire::client::{Include, Issue, QueryResult, Severity};
 use mdbn_wire::common::Value;
+use std::collections::BTreeMap;
 
 const PROJECTION_BYTES: usize = 1024 * 1024;
 
@@ -180,25 +181,29 @@ impl<S: Store> Replica<S> {
                 unreachable!("frontmatter is a map")
             };
             let effective = catalog.effective_values(&record.path, &record.types, &raw);
-            let bytes = mdbn_core::value::Value::Map(effective.clone())
-                .to_json()
-                .len();
+            // Each record field's size is measured once, however many contract
+            // fields map it.
+            let mut sizes: BTreeMap<&str, usize> = BTreeMap::new();
             let mut projections = Vec::new();
             for implementation in implementations
                 .iter()
                 .filter(|i| record.types.contains(&i.type_name))
             {
-                // Charge a conservative clone bound before Core copies mapped values.
-                let charge = bytes
-                    .checked_mul(implementation.fields.len().max(1))
-                    .and_then(|n| {
-                        n.checked_add(
-                            implementation
-                                .fields
-                                .iter()
-                                .map(|(a, b)| a.len() + b.len())
-                                .sum::<usize>(),
-                        )
+                // Charge what Core is about to copy, before it copies: every
+                // mapping clones the one value it selects. Unmapped fields are
+                // never copied, so they cost nothing here.
+                let charge = implementation
+                    .fields
+                    .iter()
+                    .try_fold(0usize, |total, (a, b)| {
+                        let value = *sizes.entry(b.as_str()).or_insert_with(|| {
+                            mdbn_core::types::select_one(&effective, b)
+                                .map_or(0, |v| v.to_json().len())
+                        });
+                        total
+                            .checked_add(value)?
+                            .checked_add(a.len())?
+                            .checked_add(b.len())
                     });
                 remaining = charge
                     .and_then(|n| remaining.checked_sub(n))

runtime/crates/replica/src/tests/describe.rs

@@ -385,16 +385,17 @@ fn contract_query_refuses_unindexed_full_windows_and_checks_session_and_selectio
     );
 }
 
-#[test]
-fn contract_query_projection_budget_is_charged_before_wide_mapping_clones() {
-    let properties = (0..128)
-        .map(|i| format!("      value{i}: {{type: boolean}}\n"))
+/// A type mapping `mappings` contract fields, each from its `source` field of
+/// JSON Schema type `kind`.
+fn wide(mappings: usize, source: &str, kind: &str) -> Vec<(String, String)> {
+    let properties = (0..mappings)
+        .map(|i| format!("      value{i}: {{type: {kind}}}\n"))
         .collect::<String>();
-    let fields = (0..128)
-        .map(|i| format!("'/value{i}': '/completed'"))
+    let fields = (0..mappings)
+        .map(|i| format!("'/value{i}': '/{source}'"))
         .collect::<Vec<_>>()
         .join(", ");
-    let (_, mut a) = configured(vec![
+    vec![
         ("mdbase.yaml".into(), "spec_version: '0.3.0'\n".into()),
         (
             "_contracts/wide.md".into(),
@@ -405,16 +406,22 @@ fn contract_query_projection_budget_is_charged_before_wide_mapping_clones() {
         (
             "_types/wide.md".into(),
             format!(
-                "---\nkind: mdbase.type\nname: wide\nschema:\n  dialect: json-schema-2020-12\n  value:\n    type: object\n    properties:\n      completed: {{type: boolean}}\nimplements:\n  - contract: acme.task\n    version: 1.0.0\n    fields: {{{fields}}}\n---\n"
+                "---\nkind: mdbase.type\nname: wide\nschema:\n  dialect: json-schema-2020-12\n  value:\n    type: object\n    properties:\n      completed: {{type: boolean}}\n      large: {{type: string}}\nimplements:\n  - contract: acme.task\n    version: 1.0.0\n    fields: {{{fields}}}\n---\n"
             ),
         ),
-    ]);
+    ]
+}
+
+#[test]
+fn contract_query_projection_budget_is_charged_before_wide_mapping_clones() {
+    // 128 mappings of one 12 KB value would copy 1.5 MB: refused before the copy.
+    let (_, mut a) = configured(wide(128, "large", "string"));
     assert!(a.r.catalog.is_valid(), "{:?}", a.r.catalog.issues());
     a.create(
         1,
         "rows/wide.md",
         &format!(
-            "---\ntype: wide\ncompleted: true\nunmapped: {}\n---\n",
+            "---\ntype: wide\ncompleted: true\nlarge: {}\n---\n",
             "x".repeat(12000)
         ),
     );
@@ -427,6 +434,37 @@ fn contract_query_projection_budget_is_charged_before_wide_mapping_clones() {
     );
 }
 
+#[test]
+fn contract_query_projection_budget_charges_mapped_values_not_the_whole_record() {
+    // Each record carries 4 KB the contract never maps. Charging the whole
+    // record once per mapping (14 x 4 KB x 60 records = 3 MB) refused every
+    // page of an ordinary library; the projection itself is 14 booleans a record.
+    let (_, mut a) = configured(wide(14, "completed", "boolean"));
+    assert!(a.r.catalog.is_valid(), "{:?}", a.r.catalog.issues());
+    for i in 0..60u8 {
+        a.create(
+            i + 1,
+            &format!("rows/{i:03}.md"),
+            &format!(
+                "---\ntype: wide\ncompleted: true\nunmapped: {}\n---\n",
+                "x".repeat(4000)
+            ),
+        );
+    }
+    settle(&mut [&mut a]);
+    let result = contract_page(&mut a, "1.0.0", None).unwrap();
+    assert_eq!(result.records.len(), 60);
+    assert!(result.records.iter().all(|r| {
+        r.implementations.len() == 1
+            && r.implementations[0].fields.0.len() == 14
+            && r.implementations[0]
+                .fields
+                .0
+                .iter()
+                .all(|(_, v)| *v == Value::Bool(true))
+    }));
+}
+
 #[test]
 fn contract_query_empty_implementation_set_is_complete_without_raw_record_inference() {
     let (_, mut a) = configured(resources());

runtime/packages/sdk/scripts/runtime-methods.json

@@ -1,6 +1,6 @@
 {
   "source": {
-    "commit": "aae332572834fbfa065c0f696017c0de3540649d",
+    "commit": "7cbf82a4f5b1ef39947ddee6424b436bc8d3daa7",
     "path": "runtime/crates/replica/src/frames.rs"
   },
   "methods": [

runtime/packages/sdk/src/application/asset-pins.json

@@ -1,11 +1,11 @@
 {
   "runtime": {
-    "sha256": "7004351583c3a79411e644fafe9f5786816d32ea058605d1905fd50666012f40",
-    "bytes": 3875815,
-    "maxBytes": 3875815,
+    "sha256": "247410a98e3a31adcd9c453cae4b607ba0528cce617d6a288bfec8745352d0b1",
+    "bytes": 3877699,
+    "maxBytes": 3877699,
     "source": {
       "repository": "mdbase-dev/mdbase-connect",
-      "commit": "aae332572834fbfa065c0f696017c0de3540649d"
+      "commit": "7cbf82a4f5b1ef39947ddee6424b436bc8d3daa7"
     }
   },
   "sqlite": {