Find a whole JSON string before a substring in FindLocation [patch]

SourceGeneratorToolkit.Test/MetadataFileTests.cs

@@ -111,6 +111,47 @@ public void ScopedFindLocationPicksTheOccurrenceAfterTheAnchor()
 		Assert.AreEqual(2, scoped.GetLineSpan().StartLinePosition.Line);
 	}
 
+	private const string CompoundNames = """
+		{"units":[
+		{"name":"SquareMeter","base":"Second"},
+		{"name":"Meter","base":"Second"}
+		]}
+		""";
+
+	[TestMethod]
+	public void FindLocationSkipsALongerNameThatContainsTheNeedle()
+	{
+		MetadataFile file = new("units.json", CompoundNames, SourceText.From(CompoundNames), "/repo/units.json");
+
+		Location location = file.FindLocation("Meter");
+
+		Assert.AreEqual(2, location.GetLineSpan().StartLinePosition.Line);
+		Assert.AreEqual("Meter", CompoundNames.Substring(location.SourceSpan.Start, location.SourceSpan.Length));
+		Assert.AreEqual('"', CompoundNames[location.SourceSpan.Start - 1]);
+	}
+
+	[TestMethod]
+	public void ScopedFindLocationSkipsALongerNameThatContainsTheAnchor()
+	{
+		MetadataFile file = new("units.json", CompoundNames, SourceText.From(CompoundNames), "/repo/units.json");
+
+		Location location = file.FindLocation("Meter", "Second");
+
+		Assert.AreEqual(2, location.GetLineSpan().StartLinePosition.Line);
+		Assert.AreEqual("Second", CompoundNames.Substring(location.SourceSpan.Start, location.SourceSpan.Length));
+	}
+
+	[TestMethod]
+	public void FindLocationStillFindsTextThatIsNotAWholeString()
+	{
+		const string text = """{"things":[{"name":"Alpha","size":12345}]}""";
+		MetadataFile file = new("things.json", text, SourceText.From(text), "/repo/things.json");
+
+		Location location = file.FindLocation("2345");
+
+		Assert.AreEqual("2345", text.Substring(location.SourceSpan.Start, location.SourceSpan.Length));
+	}
+
 	[TestMethod]
 	public void ScopedFindLocationFallsBackWhenTheAnchorIsAbsent()
 	{

SourceGeneratorToolkit/MetadataFile.cs

@@ -86,7 +86,7 @@ public Location FindLocation(string needle)
 			return Location.None;
 		}
 
-		int index = Text.IndexOf(needle, StringComparison.Ordinal);
+		int index = IndexOfToken(needle, 0);
 		return index < 0 ? Location.None : LocationAt(index, needle.Length);
 	}
 
@@ -113,16 +113,35 @@ public Location FindLocation(string anchor, string needle)
 			return Location.None;
 		}
 
-		int scope = string.IsNullOrEmpty(anchor) ? 0 : Text.IndexOf(anchor, StringComparison.Ordinal);
+		int scope = string.IsNullOrEmpty(anchor) ? 0 : IndexOfToken(anchor, 0);
 		if (scope < 0)
 		{
 			return FindLocation(needle);
 		}
 
-		int index = Text.IndexOf(needle, scope, StringComparison.Ordinal);
+		int index = IndexOfToken(needle, scope);
 		return index < 0 ? FindLocation(needle) : LocationAt(index, needle.Length);
 	}
 
+	/// <summary>
+	/// Finds <paramref name="value"/> at or after <paramref name="startIndex"/>, preferring an
+	/// occurrence that is a whole JSON string.
+	/// </summary>
+	/// <param name="value">The text to find.</param>
+	/// <param name="startIndex">Where the search starts.</param>
+	/// <returns>The index of the text itself, inside its quotes when it was found quoted, or -1.</returns>
+	/// <remarks>
+	/// A plain substring search lands inside longer names: <c>Meter</c> is found in
+	/// <c>"SquareMeter"</c>, which is a different entry. Looking for <c>"Meter"</c> first matches
+	/// only the whole string. The raw search remains the fallback so that text which is not a JSON
+	/// string on its own, such as a number or an already quoted anchor, is still found.
+	/// </remarks>
+	private int IndexOfToken(string value, int startIndex)
+	{
+		int quoted = Text.IndexOf("\"" + value + "\"", startIndex, StringComparison.Ordinal);
+		return quoted >= 0 ? quoted + 1 : Text.IndexOf(value, startIndex, StringComparison.Ordinal);
+	}
+
 	/// <summary>
 	/// Deserializes the file into <typeparamref name="T"/>.
 	/// </summary>