Add throws keyword to support validating exception messages.

Project.toml

@@ -1,7 +1,7 @@
 name = "FileCheck"
 uuid = "4e644321-382b-4b05-b0b6-5d23c3d944fb"
 authors = ["Tim Besard <[email protected]>"]
-version = "1.0"
+version = "1.1"
 
 [deps]
 LLVM_jll = "86de99a1-58d6-5da7-8064-bd56ce2e322c"

src/FileCheck.jl

@@ -25,6 +25,7 @@ function filecheck_exe(; adjust_PATH::Bool=true, adjust_LIBPATH::Bool=true)
 end
 
 function filecheck(f, input;
+    throws::Union{Nothing, Type{<:Exception}}=nothing,
     match_full_lines::Bool=false,
     strict_whitespace::Bool=false,
     ignore_case::Bool=false,
@@ -50,14 +51,33 @@ function filecheck(f, input;
             read(pipe, String)
         end
         result = nothing
+        thrown = false
         io = IOContext(pipe)
-        stats = redirect_stdio(; stdout=io, stderr=io) do
+        redirect_stdio(; stdout=io, stderr=io) do
             put!(pipe_initialized, nothing)
-            result = f(input)
+            if throws !== nothing
+                try
+                    result = f(input)
+                catch e
+                    e isa throws || rethrow()
+                    thrown = true
+                    Base.display_error(io, e, catch_backtrace())
+                end
+            else
+                result = f(input)
+            end
         end
-        if result !== nothing
-          println(io)
-          print(io, result)
+        if throws !== nothing
+            if !thrown
+                close(pipe.in)
+                fetch(reader)
+                error("Expected $throws to be thrown, but no exception was thrown")
+            end
+        else
+            if result !== nothing
+                println(io)
+                print(io, result)
+            end
         end
         close(pipe.in)
         output = fetch(reader)
@@ -228,6 +248,10 @@ These are forwarded to LLVM's FileCheck as CLI flags:
 - `check_prefixes::Vector{String}`: Use custom check prefixes (`--check-prefixes`).
 - `defines::Dict{String,String}`: Define FileCheck variables (`-Dkey=value`).
 - `allow_empty::Bool`: Allow empty check files (`--allow-empty`).
+- `throws::Type{<:Exception}`: Expect the expression to throw an exception of this type.
+  The error and backtrace are printed in standard Julia format and can be verified with
+  `@check*` directives. Raises an error if no exception is thrown; re-throws if the wrong
+  type is caught.
 
 # Examples
 
@@ -248,6 +272,11 @@ end
     @check literal=true "foo {{bar}}"
     print("foo {{bar}}")
 end
+
+@test @filecheck throws=ArgumentError begin
+    @check "ArgumentError: bad"
+    throw(ArgumentError("bad"))
+end
 ```
 """
 macro filecheck(args...)

test/runtests.jl

@@ -162,6 +162,47 @@ end
     end
 end
 
+@testset "throws" begin
+    # Basic: catch expected exception, verify error message
+    @test @filecheck throws=ErrorException begin
+        @check "ERROR: TestError"
+        error("TestError")
+    end
+
+    # Verify backtrace is included
+    @test @filecheck throws=ErrorException begin
+        @check "ERROR: TestError"
+        @check "Stacktrace:"
+        error("TestError")
+    end
+
+    # ArgumentError type
+    @test @filecheck throws=ArgumentError begin
+        @check "ArgumentError: bad arg"
+        throw(ArgumentError("bad arg"))
+    end
+
+    # Output before exception is also captured
+    @test @filecheck throws=ErrorException begin
+        @check "before"
+        @check "ERROR: boom"
+        println("before")
+        error("boom")
+    end
+
+    # No exception thrown when expected → error
+    @test_throws "no exception was thrown" @filecheck throws=ErrorException begin
+        @check "hello"
+        "hello"
+    end
+
+    # Wrong exception type → rethrown
+    @test_throws ArgumentError @filecheck throws=ErrorException begin
+        @check "hello"
+        throw(ArgumentError("wrong type"))
+    end
+end
+
 @testset "conditional checks" begin
     # cond=true: check is included
     @test @filecheck begin