[Test] make TestLogger respect maxlog (#43641)

Author: ericphanson

stdlib/Test/src/logging.jl

@@ -26,20 +26,31 @@ mutable struct TestLogger <: AbstractLogger
     min_level::LogLevel
     catch_exceptions::Bool
     shouldlog_args
+    message_limits::Dict{Any,Int}
 end
 
 TestLogger(; min_level=Info, catch_exceptions=false) =
-    TestLogger(LogRecord[], min_level, catch_exceptions, nothing)
+    TestLogger(LogRecord[], min_level, catch_exceptions, nothing, Dict{Any, Int}())
 Logging.min_enabled_level(logger::TestLogger) = logger.min_level
 
 function Logging.shouldlog(logger::TestLogger, level, _module, group, id)
-    logger.shouldlog_args = (level, _module, group, id)
-    true
+    if get(logger.message_limits, id, 1) > 0
+        logger.shouldlog_args = (level, _module, group, id)
+        true
+    else
+        false
+    end
 end
 
 function Logging.handle_message(logger::TestLogger, level, msg, _module,
                                 group, id, file, line; kwargs...)
     @nospecialize
+    maxlog = get(kwargs, :maxlog, nothing)
+    if maxlog isa Core.BuiltinInts
+        remaining = get!(logger.message_limits, id, Int(maxlog)::Int)
+        logger.message_limits[id] = remaining - 1
+        remaining > 0 || return
+    end
     push!(logger.logs, LogRecord(level, msg, _module, group, id, file, line, kwargs))
 end
 

stdlib/Test/test/runtests.jl

@@ -837,6 +837,8 @@ end
     @test occursin("Evaluated: 0.9 ≈ 0.1 (nans=true, atol=0.01)", msg)
 end
 
+erronce() = @error "an error" maxlog=1
+
 @testset "@test_logs" begin
     function foo(n)
         @info "Doing foo with n=$n"
@@ -865,6 +867,9 @@ end
 
     @test_logs (Debug,"Iteration 5") min_level=Debug match_mode=:any foo(10)
 
+    # Respect `maxlog` (#41625). We check we only find one logging message.
+    @test_logs (:error, "an error") (erronce(); erronce())
+
     # Test failures
     fails = @testset NoThrowTestSet "check that @test_logs detects bad input" begin
         @test_logs (Warn,) foo(1)