From 4c4803966e85a4b527d2595ea02754ebacf9eb90 Mon Sep 17 00:00:00 2001
From: prql-bot <107324867+prql-bot@users.noreply.github.com>
Date: Tue, 26 May 2026 07:41:16 +0000
Subject: [PATCH] fix(dotnet): correct ArgumentException constructor usage
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The five `string.IsNullOrEmpty` guards in PrqlCompiler.cs threw
`new ArgumentException(nameof(prqlQuery))`, passing the parameter name
into the message slot. The result was an ArgumentException with
`Message == "prqlQuery"` and `ParamName == null` — the opposite of what
the call looked like it intended.

Replace each guard with `ArgumentException.ThrowIfNullOrEmpty(...)`,
which matches the modern style of the adjacent
`ArgumentNullException.ThrowIfNull(options)` calls and sets ParamName
correctly. Add regression tests asserting ParamName on each entry
point; these would have caught the bug because the previous code left
ParamName null.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 .../dotnet/PrqlCompiler.Tests/CompilerTest.cs | 32 +++++++++++++++++++
 .../dotnet/PrqlCompiler/PrqlCompiler.cs       | 27 +++-------------
 2 files changed, 37 insertions(+), 22 deletions(-)

diff --git a/prqlc/bindings/dotnet/PrqlCompiler.Tests/CompilerTest.cs b/prqlc/bindings/dotnet/PrqlCompiler.Tests/CompilerTest.cs
index 6cada95f53cc..4ba64ec95717 100644
--- a/prqlc/bindings/dotnet/PrqlCompiler.Tests/CompilerTest.cs
+++ b/prqlc/bindings/dotnet/PrqlCompiler.Tests/CompilerTest.cs
@@ -57,6 +57,38 @@ public void RqToSql_ThrowsArgumentNullException_WhenOptionsNull()
         Assert.Throws<ArgumentNullException>(() => PrqlCompiler.RqToSql("{}", null!));
     }
 
+    [Fact]
+    public void Compile_ThrowsArgumentException_WhenQueryIsEmpty()
+    {
+        // Regression: previously `new ArgumentException(nameof(prqlQuery))`
+        // passed the parameter name into the message slot, leaving ParamName
+        // unset and the exception message as just "prqlQuery".
+        var ex = Assert.Throws<ArgumentException>(() => PrqlCompiler.Compile(""));
+        Assert.Equal("prqlQuery", ex.ParamName);
+    }
+
+    [Fact]
+    public void PrqlToPl_ThrowsArgumentException_WhenQueryIsEmpty()
+    {
+        var ex = Assert.Throws<ArgumentException>(() => PrqlCompiler.PrqlToPl(""));
+        Assert.Equal("prqlQuery", ex.ParamName);
+    }
+
+    [Fact]
+    public void PlToRq_ThrowsArgumentException_WhenJsonIsEmpty()
+    {
+        var ex = Assert.Throws<ArgumentException>(() => PrqlCompiler.PlToRq(""));
+        Assert.Equal("plJson", ex.ParamName);
+    }
+
+    [Fact]
+    public void RqToSql_ThrowsArgumentException_WhenJsonIsEmpty()
+    {
+        var ex = Assert.Throws<ArgumentException>(
+            () => PrqlCompiler.RqToSql("", new PrqlCompilerOptions()));
+        Assert.Equal("rqJson", ex.ParamName);
+    }
+
     [Fact]
     public void Compile_HandlesNonAsciiInput()
     {
diff --git a/prqlc/bindings/dotnet/PrqlCompiler/PrqlCompiler.cs b/prqlc/bindings/dotnet/PrqlCompiler/PrqlCompiler.cs
index ac70a7df5895..dc27544d9faa 100644
--- a/prqlc/bindings/dotnet/PrqlCompiler/PrqlCompiler.cs
+++ b/prqlc/bindings/dotnet/PrqlCompiler/PrqlCompiler.cs
@@ -18,10 +18,7 @@ public static partial class PrqlCompiler
     /// <exception cref="FormatException"><paramref name="prqlQuery"/> cannot be compiled.</exception>
     public static Result Compile(string prqlQuery)
     {
-        if (string.IsNullOrEmpty(prqlQuery))
-        {
-            throw new ArgumentException(nameof(prqlQuery));
-        }
+        ArgumentException.ThrowIfNullOrEmpty(prqlQuery);
 
         return Compile(prqlQuery, new PrqlCompilerOptions());
     }
@@ -37,11 +34,7 @@ public static Result Compile(string prqlQuery)
     /// <exception cref="FormatException"><paramref name="prqlQuery"/> cannot be compiled.</exception>
     public static Result Compile(string prqlQuery, PrqlCompilerOptions options)
     {
-        if (string.IsNullOrEmpty(prqlQuery))
-        {
-            throw new ArgumentException(nameof(prqlQuery));
-        }
-
+        ArgumentException.ThrowIfNullOrEmpty(prqlQuery);
         ArgumentNullException.ThrowIfNull(options);
 
         var targetPtr = options.Target is null
@@ -72,10 +65,7 @@ public static Result Compile(string prqlQuery, PrqlCompilerOptions options)
     /// <remarks>https://docs.rs/prqlc/latest/</remarks>
     public static Result PrqlToPl(string prqlQuery)
     {
-        if (string.IsNullOrEmpty(prqlQuery))
-        {
-            throw new ArgumentException(nameof(prqlQuery));
-        }
+        ArgumentException.ThrowIfNullOrEmpty(prqlQuery);
 
         var nativeResult = PrqlToPlExtern(prqlQuery);
         return new Result(nativeResult);
@@ -91,10 +81,7 @@ public static Result PrqlToPl(string prqlQuery)
     /// <remarks>https://docs.rs/prqlc/latest/</remarks>
     public static Result PlToRq(string plJson)
     {
-        if (string.IsNullOrEmpty(plJson))
-        {
-            throw new ArgumentException(nameof(plJson));
-        }
+        ArgumentException.ThrowIfNullOrEmpty(plJson);
 
         var nativeResult = PlToRqExtern(plJson);
         return new Result(nativeResult);
@@ -112,11 +99,7 @@ public static Result PlToRq(string plJson)
     /// <remarks>https://docs.rs/prqlc/latest/</remarks>
     public static Result RqToSql(string rqJson, PrqlCompilerOptions options)
     {
-        if (string.IsNullOrEmpty(rqJson))
-        {
-            throw new ArgumentException(nameof(rqJson));
-        }
-
+        ArgumentException.ThrowIfNullOrEmpty(rqJson);
         ArgumentNullException.ThrowIfNull(options);
 
         var targetPtr = options.Target is null