Work around for JuliaLang/julia#19979

Retry.jl used to use try/catch inside the catch block's "@ignore if ..."
condition. The purpose of this was to treat if conditions that throw
errors as false. e.f. @ignore if e.reason == "Foo" end might throw an
exception if e does not have a reason field. Retry.jl used to allow this
and treat it as false.

At present doing a nested try/catch in a catch block causes the Julia
stacktrace to be corrupted: JuliaLang/julia#19979 (comment)

After this commit, Retry.jl not requires @ignore if conditions to return
true or false and not throw exceptions.

The ecode() function has been exported to allow replacing

    @ignore if e.code == "404" end

with

    @ignore if ecode(e) == "404" end

src/Retry.jl

@@ -1,6 +1,11 @@
 module Retry
 
-export @repeat, @protected
+__precompile__(true)
+
+export @repeat, @protected, efield, ecode
+
+efield(x, f, default=nothing) = f in fieldnames(x) ? getfield(x, f) : default
+ecode(x) = efield(x, :code)
 
 include("repeat_try.jl")
 include("protected_try.jl")

src/protected_try.jl

@@ -62,7 +62,6 @@ macro protected(try_expr::Expr)
 
             if_expr = check_macro_if(expr)
             (condition, action) = if_expr.args
-            if_expr.args[1] = :(try $condition catch false end)
 
             # Clear exception variable at end of "@ignore if..." block...
             push!(action.args, :($exception = nothing))

src/repeat_try.jl

@@ -126,7 +126,9 @@ end
 
 function esc_args!(expr::Expr)
     for (i, arg) in enumerate(expr.args)
-        expr.args[i] = esc(arg)
+        if isa(arg, Symbol) || arg.head != :line
+            expr.args[i] = esc(arg)
+        end
     end
 end
 
@@ -140,11 +142,8 @@ macro repeat(max, try_expr::Expr)
     esc_args!(try_expr)
     try_expr.args[3] = catch_block
 
-    # Check for nothing exception at start of catch block...
-    unshift!(catch_block.args, :($exception == nothing && rethrow($exception)))
-
-    # Rethrow at end of catch block...
-    push!(catch_block.args, :($exception == nothing || rethrow($exception)))
+    max = esc(max)
+    exception = esc(exception)
 
     for (i, expr) in enumerate(catch_block.args)
 
@@ -159,25 +158,24 @@ macro repeat(max, try_expr::Expr)
 
             if_expr = check_macro_if(expr)
             (condition, action) = if_expr.args
-            if_expr.args[1] = :(try $(esc(condition)) catch e false end)
+            if_expr.args[1] = esc(condition)
+            esc_args!(action)
 
             # Clear exception variable at end of "@ignore if..." block...
             if handler == "@ignore"
-                push!(action.args, :($exception = nothing))
+                push!(action.args, :(ignore = true))
             end
 
-            esc_args!(action)
-
             # Loop to try again at end of "@retry if..." block...
             if handler == "@retry"
-                push!(action.args, :(if i < $(esc(max)) continue end))
+                push!(action.args, :(if i < $max continue end))
             end
 
             # Add exponentially increasing delay with random jitter,
             # and loop to try again at end of "@delay_retry if..." block...
             if handler == "@delay_retry"
                 push!(action.args, quote
-                    if i < $(esc(max))
+                    if i < $max
                         sleep(delay * (0.8 + (0.4 * rand())))
                         delay *= 10
                         continue
@@ -187,17 +185,24 @@ macro repeat(max, try_expr::Expr)
 
             # Replace @ignore/@retry macro call with modified if expression...
             catch_block.args[i] = if_expr
-        else
+        elseif expr.head != :line
             catch_block.args[i] = esc(expr)
         end
     end
 
+    # Check for nothing exception at start of catch block...
+    insert!(catch_block.args, 2, :($exception == nothing && rethrow()))
+    unshift!(catch_block.args, :(ignore = false))
+
+    # Rethrow at end of catch block...
+    push!(catch_block.args, :(ignore || rethrow($exception)))
+
     # Build retry expression...
     quote
         delay = 0.05
         result = false
 
-        for i in 1:$(esc(max))
+        for i in 1:$max
             result = $try_expr
             break
         end
@@ -207,7 +212,6 @@ macro repeat(max, try_expr::Expr)
 end
 
 
-
 #==============================================================================#
 # End of file.
 #==============================================================================#

test/runtests.jl

@@ -29,7 +29,7 @@ end
 @test_throws TestException  @protected try
                                 throw(TestException(7))
                             catch e
-                                @ignore if e.code == "Nothing to see here" end
+                                @ignore if ecode(e) == "Nothing to see here" end
                             end
 
 
@@ -38,7 +38,7 @@ end
 @test   @protected try
             throw(TestException(7))
         catch e
-            @ignore if e.code == 7 end
+            @ignore if ecode(e) == 7 end
         end
 
 
@@ -58,7 +58,7 @@ count = 0
                                 global count += 1
                                 throw(TestException(7))
                             catch e
-                                @retry if e.code == 7 end
+                                @retry if ecode(e) == 7 end
                             end
 @test count == 4
 
@@ -70,7 +70,7 @@ count = 0
                                 global count += 1
                                 throw(TestException(5))
                             catch e
-                                @retry if e.code == 7 end
+                                @retry if ecode(e) == 7 end
                             end
 @test count == 1
 
@@ -82,7 +82,7 @@ count = 0
             global count += 1
             throw(TestException(7))
         catch e
-            @ignore if e.code == 7 end
+            @ignore if ecode(e) == 7 end
         end
 @test count == 1
 
@@ -102,7 +102,7 @@ i = -1
                                 count += 1
                                 throw(TestException(7))
                             catch e
-                                @delay_retry if e.code == 7 end
+                                @delay_retry if ecode(e) == 7 end
                             end
 @test count == 3
 
@@ -118,8 +118,8 @@ count = 0
                                 global count += 1
                                 throw(TestException(count))
                             catch e
-                                @retry if e.code < 3 end
-                                @ignore if e.code == 3 end
+                                @retry if ecode(e) < 3 end
+                                @ignore if ecode(e) == 3 end
                             end
 @test count == 2
 
@@ -131,8 +131,8 @@ count = 0
                                 global count += 1
                                 throw(TestException(count))
                             catch e
-                                @retry if e.code < 3 end
-                                @ignore if e.code == 3 end
+                                @retry if ecode(e) < 3 end
+                                @ignore if ecode(e) == 3 end
                             end
 @test count == 3
 
@@ -144,8 +144,8 @@ count = 0
                                 global count += 1
                                 throw(TestException(count))
                             catch e
-                                @retry if e.code < 3 end
-                                @ignore if e.code == 3 end
+                                @retry if ecode(e) < 3 end
+                                @ignore if ecode(e) == 3 end
                             end
 @test count == 3