Fix validated part uri equality

[alinpahontu2912]

Fixes #129927
PR #118574 added object.Equals/GetHashCode overrides to ValidatedPartUri (which derives from System.Uri) to support case-insensitive part-name matching. This broke the inherited Uri equality contract: Equals became asymmetric against a plain System.Uri of the same value, and GetHashCode became inconsistent with System.Uri.GetHashCode(). Consumers mixing ValidatedPartUri with plain System.Uri in HashSet/Dictionary<Uri,_> (e.g. the Open XML SDK) got incorrect lookup results.

Revert the Equals(object?)/GetHashCode() overrides, restoring the original CA1067 suppression. ValidatedPartUri once again inherits Uri's value-equality, matching plain System.Uri semantics.
Keep the case-insensitive Compare()/IComparable/ IEquatable logic, which is what makes Package.cs's SortedList<ValidatedPartUri, PackagePart> lookups case-insensitive (fixing #112783 for that path) and is unaffected by this change.
Add PackUriHelper.ValidatedPartUriEqualityComparer, an internal IEqualityComparer providing case-insensitive equality/hashing, and use it explicitly in ZipPackage's content-type override dictionary. Without this, removing GetHashCode() would leave that Dictionary<ValidatedPartUri,_> with a hash/equals mismatch (case-insensitive Equals via IEquatable, case-sensitive hash via inherited Uri.GetHashCode()), silently dropping parts whose zip entry name casing differs from their [Content_Types].xml Override PartName.
Add regression tests covering the Uri equality contract and the content-type override case-insensitivity behavior.

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[Copilot]

Pull request overview

This PR restores PackUriHelper.ValidatedPartUri’s compatibility with System.Uri’s object.Equals/GetHashCode contract (so it can safely interoperate with plain Uri instances in hash-based collections), while keeping case-insensitive part-name semantics where needed via an explicit internal comparer.

Changes:

• Remove ValidatedPartUri’s Equals(object?) / GetHashCode() overrides to re-align with base System.Uri equality/hashing behavior.
• Introduce PackUriHelper.ValidatedPartUriEqualityComparer and use it for ZipPackage’s override content-type dictionary to preserve case-insensitive override lookups without changing Uri’s base contract.
• Add regression tests covering (1) the Uri equality/hash contract and (2) case-insensitive content-type override resolution.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/libraries/System.IO.Packaging/tests/PartPieceTests.cs	Adds regression tests for ValidatedPartUri equality/hash compatibility and for case-insensitive override content-type lookup.
src/libraries/System.IO.Packaging/src/System/IO/Packaging/ZipPackage.cs	Updates the override dictionary to use the new ValidatedPartUriEqualityComparer.
src/libraries/System.IO.Packaging/src/System/IO/Packaging/PackUriHelper.cs	Removes Equals(object?)/GetHashCode() overrides from ValidatedPartUri and adds the internal equality comparer type.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/libraries/System.IO.Packaging/src/System/IO/Packaging/ZipPackage.cs:949

• EnsureOverrideDictionary() now uses ValidatedPartUriEqualityComparer, but the comment still says comparison is done using PartUriComparer. This is misleading when debugging override lookups and should be updated to reflect the actual comparer in use.

                // The part Uris are stored in the Override Dictionary in their original form , but they are compared
                // in a normalized manner using the PartUriComparer

src/libraries/System.IO.Packaging/tests/PartPieceTests.cs:377

• The symmetry assertion can pass even if both directions return false. Since this test is specifically about the equality contract for two URIs that should be value-equal, it should assert both directions are true (not just equal).

            // object.Equals must be symmetric.
            Assert.Equal(a.Equals(b), b.Equals(a));

src/libraries/System.IO.Packaging/src/System/IO/Packaging/PackUriHelper.cs:607

• The CA1067 suppression comment is self-contradictory ("Override Equals...; not overriding...") and doesn’t explain the real intent (preserving System.Uri’s equality/hash contract). This is easy to misread during future maintenance.

#pragma warning disable CA1067 // Override Equals because it implements IEquatable<T>; not overriding to avoid possible regressions in code that's working
        internal sealed class ValidatedPartUri : Uri, IComparable<ValidatedPartUri>, IEquatable<ValidatedPartUri>
#pragma warning restore CA1067

src/libraries/System.IO.Packaging/src/System/IO/Packaging/PackUriHelper.cs:908

• ValidatedPartUri.NormalizedPartUriString is already case-folded to upper invariant (see GetNormalizedPartUriString), so using OrdinalIgnoreCase hashing here is unnecessary and slightly more expensive/misleading. Using ordinal hashing better matches the comparer’s actual semantics (ordinal compare on normalized strings).

            public int GetHashCode(ValidatedPartUri obj)
                => StringComparer.OrdinalIgnoreCase.GetHashCode(obj.NormalizedPartUriString);

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[rzikm]

Some copilot suggestions seem relevant, otherwise LGTM if tests pass

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/libraries/System.IO.Packaging/src/System/IO/Packaging/PackUriHelper.cs:907

• ValidatedPartUri.NormalizedPartUriString is already case-folded to upper-invariant (see GetNormalizedPartUriString), so using StringComparer.OrdinalIgnoreCase here does extra work without changing behavior. Using StringComparer.Ordinal keeps equality/hash consistency while reducing hashing cost.

            public int GetHashCode(ValidatedPartUri obj)
                => StringComparer.OrdinalIgnoreCase.GetHashCode(obj.NormalizedPartUriString);

[MihaZupan]

So besides the hash code inconsistency, it seems that this type is also breaking invariants in other ways?

E.g. a.Equals(b) may not mean that a.Equals((object)b)
or a.Compare(b) == 0 may not mean that a == b?

These seem like pre-existing issues though

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/libraries/System.IO.Packaging/src/System/IO/Packaging/PackUriHelper.cs:605

• The CA1067 suppression comment is contradictory (it says "Override Equals" while the code intentionally does not override object.Equals/GetHashCode). This makes the rationale unclear for future maintainers.

#pragma warning disable CA1067 // Override Equals because it implements IEquatable<T>; not overriding to avoid possible regressions in code that's working

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/libraries/System.IO.Packaging/src/System/IO/Packaging/PackUriHelper.cs:907

• ValidatedPartUri.NormalizedPartUriString is always upper-cased (see GetNormalizedPartUriString()), so using StringComparer.OrdinalIgnoreCase here is redundant and adds extra work on every hash computation. Using StringComparer.Ordinal is sufficient and keeps the comparer consistent with the normalization strategy.

            public int GetHashCode(ValidatedPartUri obj)
                => StringComparer.OrdinalIgnoreCase.GetHashCode(obj.NormalizedPartUriString);

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.