Lower severity of the diagnostic when the "source" of a symbol graph relationship is missing.

Since the solution is for the tool that created the symbol graph file to not emit that relationship, DocC can safely skip it and proceed with the build. This issue isn't severe enough to fail the build.

Author: d-ronnqvist

Sources/SwiftDocC/Infrastructure/Symbol Graph/SymbolGraphRelationshipsBuilder.swift

@@ -18,7 +18,7 @@ struct SymbolGraphRelationshipsBuilder {
         static func sourceNotFound(_ relationship: SymbolGraph.Relationship) -> Problem {
             return Problem(
                 diagnostic: Diagnostic(
-                    source: nil, severity: .error, range: nil,identifier: "org.swift.docc.SymbolNodeNotFound",
+                    source: nil, severity: .warning, range: nil,identifier: "org.swift.docc.SymbolNodeNotFound",
                     summary: "Source symbol \(relationship.source.singleQuoted) not found locally, from \(relationship.kind.rawValue.singleQuoted) relationship to \(relationship.target.singleQuoted)",
                     explanation: """
                     The "source" of a symbol graph relationship should always refer to a symbol in the same symbol graph file.

Tests/SwiftDocCUtilitiesTests/ConvertActionTests.swift

@@ -900,10 +900,7 @@ class ConvertActionTests: XCTestCase {
                 temporaryDirectory: testDataProvider.uniqueTemporaryDirectory())
             let result = try action.perform(logHandle: .none)
 
-            XCTAssert(
-                result.didEncounterError,
-                "We expect errors to occur during during conversion of the bad test bundle."
-            )
+            XCTAssertFalse(result.didEncounterError, "The issues with this test bundle are not severe enough to fail the build.")
 
             // Verify that the build output folder from the former successful conversion
             // still exists after this failure.
@@ -945,7 +942,7 @@ class ConvertActionTests: XCTestCase {
                 Digest.Diagnostic(
                     start: nil,
                     source: nil,
-                    severity: .error,
+                    severity: .warning,
                     summary: "Source symbol 's:5MyKit0A5ProtocolP' not found locally, from 'conformsTo' relationship to 's:5Foundation0A5EarhartP'",
                     explanation: """
                     The "source" of a symbol graph relationship should always refer to a symbol in the same symbol graph file.
@@ -2421,8 +2418,8 @@ class ConvertActionTests: XCTestCase {
         )
         let result = try action.perform(logHandle: .none)
 
-        XCTAssertEqual(engine.problems.count, 1, "\(ConvertAction.self) didn't filter out diagnostics above the 'error' level.")
-        XCTAssert(result.didEncounterError)
+        XCTAssertEqual(engine.problems.count, 0, "\(ConvertAction.self) didn't filter out diagnostics at-or-above the 'error' level.")
+        XCTAssertFalse(result.didEncounterError, "The issues with this test bundle are not severe enough to fail the build.")
     }
 
     func testDiagnosticLevelIgnoredWhenAnalyzeIsPresent() throws {
@@ -2461,7 +2458,7 @@ class ConvertActionTests: XCTestCase {
 
         XCTAssertEqual(engine.problems.count, 2, "\(ConvertAction.self) shouldn't filter out diagnostics when the '--analyze' flag is passed")
         XCTAssertEqual(engine.problems.map { $0.diagnostic.identifier }, ["org.swift.docc.Article.Title.NotFound", "org.swift.docc.SymbolNodeNotFound"])
-        XCTAssert(result.didEncounterError)
+        XCTAssertFalse(result.didEncounterError, "The issues with this test bundle are not severe enough to fail the build.")
         XCTAssert(engine.problems.contains(where: { $0.diagnostic.severity == .warning }))
     }
 
@@ -2495,9 +2492,7 @@ class ConvertActionTests: XCTestCase {
             temporaryDirectory: testDataProvider.uniqueTemporaryDirectory(),
             diagnosticLevel: "error"
         )
-        XCTAssertThrowsError(try action.performAndHandleResult(logHandle: .none)) { error in
-            XCTAssert(error is ErrorsEncountered, "Unexpected error type thrown by \(ConvertAction.self)")
-        }
+        XCTAssertNoThrow(try action.performAndHandleResult(logHandle: .none))
     }
 
     func testWritesDiagnosticFileWhenThrowingError() throws {
@@ -2537,9 +2532,7 @@ class ConvertActionTests: XCTestCase {
 
         // TODO: Support TestFileSystem in DiagnosticFileWriter
         XCTAssertFalse(FileManager.default.fileExists(atPath: diagnosticFile.path), "Diagnostic file doesn't exist before")
-        XCTAssertThrowsError(try action.performAndHandleResult(logHandle: .none)) { error in
-            XCTAssert(error is ErrorsEncountered, "Unexpected error type thrown by \(ConvertAction.self)")
-        }
+        XCTAssertNoThrow(try action.performAndHandleResult(logHandle: .none))
         XCTAssertTrue(FileManager.default.fileExists(atPath: diagnosticFile.path), "Diagnostic file exist after")
     }
 
@@ -2612,7 +2605,7 @@ class ConvertActionTests: XCTestCase {
             temporaryDirectory: testDataProvider.uniqueTemporaryDirectory()
         )
 
-        XCTAssertThrowsError(try action.performAndHandleResult(logHandle: .none), "The test bundle should have thrown an error about an incomplete symbol graph file")
+        XCTAssertNoThrow(try action.performAndHandleResult(logHandle: .none))
         XCTAssert(testDataProvider.fileExists(atPath: digestFileURL.path), "The digest file should have been written even though compilation errors occurred")
 
         let data = try testDataProvider.contentsOfURL(digestFileURL)