fix(browser): compare resource inventories with directional coverage

src/artifacts/pyinstaller/MarshalSubset.test.ts

@@ -20,11 +20,6 @@ it("reads a Python 3.9 reference-flagged PYZ table", () => {
   ]);
 });
 
-it("reads marshal one-byte string tags as Latin-1", () => {
-  for (const hex of ["6101000000e9", "4101000000e9", "7a01e9", "5a01e9"])
-    expect(readMarshalSubset(bytes(hex))).toEqual({ ok: true, value: "é" });
-});
-
 it("decodes CPython marshal Unicode with surrogatepass", () => {
   expect(
     readMarshalSubset(

src/artifacts/pyinstaller/MarshalSubset.ts

@@ -168,8 +168,14 @@ const readAsciiBytes = (
 ): Result<string, PyInstallerFailure> => {
   const bytes = readBytes(cursor, length);
   if (!bytes.ok) return bytes;
-  // These tags use CPython's one-byte Unicode constructor, not an ASCII check.
-  return ok(bytes.value.toString("latin1"));
+  if (bytes.value.some((byte) => byte > 0x7f))
+    return err(
+      pyInstallerFailure(
+        "format",
+        "PYZ marshal ASCII string contains a non-ASCII byte",
+      ),
+    );
+  return ok(bytes.value.toString("ascii"));
 };
 
 const readUtf8 = (

src/domain/webCaptureDiff.resources.test.ts

@@ -110,3 +110,47 @@ describe("web resource comparison identity and optional size", () => {
     });
   });
 });
+
+it.each([
+  [[128, 256], [128], [false, true], "unknown"],
+  [[128], [256], [true, true], "unknown"],
+  [[128], [128], [true, true], "unknown"],
+  [[128], [128, 256], [false, true], "changed"],
+  [[], [128], [false, true], "changed"],
+  [[128], [], [true, true], "unknown"],
+  [[128], [null], [false, true], "unknown"],
+] as const)(
+  "uses directional resource coverage for %j vs %j (limited=%j): %s",
+  (leftSizes, rightSizes, [leftLimited, rightLimited], status) => {
+    const before = capture(leftSizes.map((size) => resource(size)));
+    const after = capture(rightSizes.map((size) => resource(size)));
+    if (leftLimited) before.completeness.truncated_sections.push("resources");
+    if (rightLimited) after.completeness.truncated_sections.push("resources");
+    for (const [left, right] of [
+      [before, after],
+      [after, before],
+    ] as const)
+      expect(compareResources(left, right)).toMatchObject({
+        status,
+        total_changes: status === "changed" ? 1 : 0,
+        changes:
+          status === "changed"
+            ? [
+                {
+                  identity: expect.stringMatching(/^resg_/u),
+                  change:
+                    left.resources.length === 0
+                      ? "added"
+                      : right.resources.length === 0
+                        ? "removed"
+                        : "modified",
+                },
+              ]
+            : [],
+        reason:
+          status === "changed"
+            ? null
+            : expect.stringContaining("Resource inventory"),
+      });
+  },
+);

src/domain/webCaptureDiff.ts

@@ -213,9 +213,8 @@ const compareWebCaptureDimensions = (
     resources: compareResources(
       before.resources,
       after.resources,
-      sectionsComplete(before, ["resources"]) &&
-        sectionsComplete(after, ["resources"]),
-      "Resource inventory or content-size evidence was incomplete in at least one observation.",
+      sectionsComplete(before, ["resources"]),
+      sectionsComplete(after, ["resources"]),
     ),
     network: networkDimension(before, after),
     metadata: compareAggregate(
@@ -235,9 +234,12 @@ const compareWebCaptureDimensions = (
 const compareResources = (
   before: WebPageInspection["resources"],
   after: WebPageInspection["resources"],
-  complete: boolean,
-  reason: string,
+  beforeComplete: boolean,
+  afterComplete: boolean,
 ): Dimension => {
+  const reason =
+    "Resource inventory or content-size evidence was incomplete in at least one observation.";
+  const complete = beforeComplete && afterComplete;
   const left = resourceGroups(before);
   const right = resourceGroups(after);
   const changes: Change[] = [];
@@ -246,12 +248,14 @@ const compareResources = (
     const leftSizes = left.get(identity);
     const rightSizes = right.get(identity);
     if (leftSizes === undefined || rightSizes === undefined) {
-      if (!complete) unresolved = true;
-      else
+      const absenceProven =
+        leftSizes === undefined ? beforeComplete : afterComplete;
+      if (absenceProven)
         changes.push({
           identity,
           change: leftSizes === undefined ? "added" : "removed",
         });
+      else unresolved = true;
       continue;
     }
     // Stable inventories deduplicate identical observations. A null size also
@@ -261,7 +265,12 @@ const compareResources = (
       unresolved = true;
       continue;
     }
-    if (!sameResourceSizes(leftSizes, rightSizes))
+    // A partial set can omit any size variant. Only a complete peer can
+    // contradict a retained variant, including when the other side is partial.
+    if (
+      (beforeComplete && !resourceSizesContained(rightSizes, leftSizes)) ||
+      (afterComplete && !resourceSizesContained(leftSizes, rightSizes))
+    )
       changes.push({ identity, change: "modified" });
   }
   if (changes.length > 0)
@@ -292,11 +301,10 @@ const resourceGroups = (
   return groups;
 };
 
-const sameResourceSizes = (
-  left: ReadonlySet<number | null>,
-  right: ReadonlySet<number | null>,
-): boolean =>
-  left.size === right.size && [...left].every((size) => right.has(size));
+const resourceSizesContained = (
+  observed: ReadonlySet<number | null>,
+  complete: ReadonlySet<number | null>,
+): boolean => [...observed].every((size) => complete.has(size));
 
 type BodyShapeSources = {
   readonly request: boolean;

src/python/PythonPycParser.test.ts

@@ -407,30 +407,6 @@ it("charges long digits to the string budget and keeps large previews bounded",
   );
 });
 
-it("reads marshal one-byte string tags as Latin-1 with Unicode identity", () => {
-  for (const tag of [0x61, 0x41, 0x7a, 0x5a]) {
-    const encoded = Buffer.concat([
-      Buffer.from([tag]),
-      tag === 0x61 || tag === 0x41 ? u32(1) : Buffer.from([1]),
-      Buffer.from([0xe9]),
-    ]);
-    const sameUnicode = marshalUnicode(Buffer.from("é", "utf8"));
-    const set = Buffer.concat([
-      Buffer.from([0x3c]),
-      u32(2),
-      encoded,
-      sameUnicode,
-    ]);
-    const report = root(parse(withConsts([encoded, set])));
-    expect(report.consts[0]).toMatchObject({
-      kind: "str",
-      value: "é",
-      bytes: 1,
-    });
-    expect(report.consts[1]).toEqual({ kind: "set", length: 1 });
-  }
-});
-
 it("decodes marshal strings with CPython surrogatepass rules", () => {
   const report = parse(
     withConsts([marshalUnicode(Buffer.from("efbbbf73eda080efbbbf", "hex"))]),
@@ -1558,36 +1534,6 @@ it("hashes a long TYPE_REF tuple chain without recursing", () => {
   expect(pythonPycSchema.safeParse(report).success).toBe(true);
 });
 
-it("hashes shallow TYPE_REF code chains without using the JavaScript stack", () => {
-  const links = 3000;
-  const codes = Array.from({ length: links }, (_, index) =>
-    marshalCode("py311", {
-      flagged: true,
-      name: "f",
-      consts: index === 0 ? [Buffer.from([0x4e])] : [marshalRef(index - 1)],
-    }),
-  );
-  const bytes = Buffer.concat([
-    pythonPycHeader(3531),
-    marshalCode("py311", {
-      constsObject: Buffer.concat([
-        Buffer.from([0x28]),
-        u32(links + 1),
-        ...codes,
-        Buffer.from([0x3c]),
-        u32(1),
-        marshalRef(links - 1),
-      ]),
-    }),
-  ]);
-  const report = parseWith(bytes, { max_objects: 65_536 });
-  expect(root(report).consts.at(-1)).toEqual({ kind: "set", length: 1 });
-  expect(report.coverage).toMatchObject({
-    status: "complete",
-    code_objects: links + 1,
-  });
-});
-
 it("rejects code CPython treats as corrupt instead of complete coverage", () => {
   const file = (
     layout: "py37" | "py38" | "py311",

src/python/PythonPycParser.ts

@@ -332,7 +332,7 @@ class MarshalReader {
   readonly #codeKeys = new WeakMap<CodeNode, string>();
   readonly #codeIdentities = new WeakMap<CodeNode, number>();
   readonly #codeEquality = new WeakMap<CodeNode, CodeEquality>();
-  /** Completed Python hashability checks per code object. */
+  /** Python hashability per code object. False while that check is in progress. */
   readonly #codeHashable = new WeakMap<CodeNode, boolean>();
   /** Tuples whose items are still being read; CPython cannot hash them yet. */
   readonly #readingTuples = new WeakSet<MarshalValue>();
@@ -436,19 +436,13 @@ class MarshalReader {
         };
       case TYPE_INTERNED:
       case TYPE_UNICODE:
-        return this.string(
-          this.nonNegativeInt32("Marshal string length"),
-          "utf8",
-        );
+        return this.utf8(this.nonNegativeInt32("Marshal string length"), false);
       case TYPE_ASCII:
       case TYPE_ASCII_INTERNED:
-        return this.string(
-          this.nonNegativeInt32("Marshal string length"),
-          "latin1",
-        );
+        return this.utf8(this.nonNegativeInt32("Marshal string length"), true);
       case TYPE_SHORT_ASCII:
       case TYPE_SHORT_ASCII_INTERNED:
-        return this.string(this.u8(), "latin1");
+        return this.utf8(this.u8(), true);
       case TYPE_TUPLE:
         return this.sequenceValue(
           "tuple",
@@ -1315,70 +1309,13 @@ class MarshalReader {
   #isCodeHashable(node: CodeNode): boolean {
     const known = this.#codeHashable.get(node);
     if (known !== undefined) return known;
-    const frames: { value: MarshalValue; finish: boolean }[] = [
-      { value: { kind: "code", value: node }, finish: false },
-    ];
-    const gray = new Set<MarshalValue | CodeNode>();
-    const complete = new Set<MarshalValue>();
-    const reject = (): false => {
-      this.#codeHashable.set(node, false);
-      return false;
-    };
-    while (frames.length > 0) {
-      this.#takeKeyStep();
-      const frame = frames.pop()!;
-      const value = frame.value;
-      const identity = value.kind === "code" ? value.value : value;
-      if (frame.finish) {
-        gray.delete(identity);
-        if (value.kind === "code") {
-          const material =
-            this.#codeEquality.get(value.value) ??
-            malformed("Code object is missing equality material.");
-          // Child code checks are now complete, so the existing tuple key
-          // walker preserves its equality and expansion budgets without recursion.
-          const hashable =
-            this.#equalityKey(material.constsTuple, "hash") !== null;
-          this.#codeHashable.set(value.value, hashable);
-          if (!hashable) return reject();
-        } else complete.add(value);
-        continue;
-      }
-      if (value.kind === "code") {
-        const cached = this.#codeHashable.get(value.value);
-        if (cached === false) return reject();
-        if (cached === true) continue;
-      } else {
-        const cached = this.#keyCache.get(value);
-        if (cached === null) return reject();
-        if (cached !== undefined || complete.has(value)) continue;
-      }
-      if (
-        gray.has(identity) ||
-        this.#readingTuples.has(value) ||
-        value.kind === "list" ||
-        value.kind === "set" ||
-        value.kind === "dict" ||
-        value.kind === "null"
-      )
-        return reject();
-      const children =
-        value.kind === "code"
-          ? [
-              (
-                this.#codeEquality.get(value.value) ??
-                malformed("Code object is missing equality material.")
-              ).constsTuple,
-            ]
-          : value.kind === "tuple" || value.kind === "frozenset"
-            ? value.items
-            : [];
-      gray.add(identity);
-      frames.push({ value, finish: true });
-      for (let index = children.length - 1; index >= 0; index -= 1)
-        frames.push({ value: children[index]!, finish: false });
-    }
-    return true;
+    this.#codeHashable.set(node, false);
+    const material =
+      this.#codeEquality.get(node) ??
+      malformed("Code object is missing equality material.");
+    const hashable = this.#equalityKey(material.constsTuple, "hash") !== null;
+    this.#codeHashable.set(node, hashable);
+    return hashable;
   }
 
   #codeIdentity(node: CodeNode): number {
@@ -1555,20 +1492,17 @@ class MarshalReader {
     );
   }
 
-  string(length: number, encoding: "latin1" | "utf8"): MarshalValue {
+  utf8(length: number, ascii: boolean): MarshalValue {
     const bytes = this.blob(length);
-    if (encoding === "latin1") {
-      // CPython reads the ASCII-tagged forms as one-byte Unicode, even when
-      // high bytes appear. Identity must agree with the UTF-8 string form.
-      const value = bytes.toString("latin1");
+    if (ascii) {
+      if (bytes.some((byte) => byte > 0x7f))
+        malformed("Marshal ASCII string contains a non-ASCII byte.");
       return {
         kind: "str",
-        value,
+        value: bytes.toString("latin1"),
         previewEnd: Math.min(length, PYTHON_PYC_CONST_PREVIEW_LIMIT),
         bytes: length,
-        raw: bytes.some((byte) => byte > 0x7f)
-          ? Buffer.from(value, "utf8")
-          : bytes,
+        raw: bytes,
       };
     }
     const decoded = decodeMarshalUtf8(bytes, PYTHON_PYC_CONST_PREVIEW_LIMIT);