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improve(core): upgrade trace macro and add custom assert messages #1579

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575e2f4
Improve trace and assert macros to display expressions, use prn, and …
sqrew Aug 16, 2026
c68e306
test: verify trace macro output with file-path-print-length short
sqrew Sep 1, 2026
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46 changes: 26 additions & 20 deletions core/Debug.carp
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Original file line number Diff line number Diff line change
Expand Up @@ -39,31 +39,37 @@ immediately, raising a `SIGABRT` if it fails.")
(IO.println &(fmt "Invalid memory balance: %d" (Debug.memory-balance)))
(ignore (System.exit 1)))))))

(doc trace "prints the value of an expression to `stdout`, then returns its value.")
(doc trace "prints the expression and its value to `stdout`, then returns its value.")
(defmacro trace [x]
(let [sym (gensym)]
(let [sym (gensym)
x-str (str x)]
`(let-do [%sym %x]
; we use eval here to ensure we resolve the symbol before putting it
; into file, line, and column
(IO.println
(ref
(fmt "%s:%d:%d: %s"
%(eval `(file %x))
%(eval `(line %x))
%(eval `(column %x))
&(str %sym))))
%sym)
)
)
(IO.println
(ref
(fmt "%s:%d:%d: %s = %s"
%(eval `(file %x))
%(eval `(line %x))
%(eval `(column %x))
%x-str
&(prn &%sym))))
%sym)))

(doc leak-array "leaks some memory. This function is useful for testing tools that detect leaks.")
(register leak-array (Fn [a] ()) "Debug_leak_MINUS_array")

)

;; Crash the program with an error message unless the expression evaluates to 'true'.
(defmacro assert [expr]
`(unless (= true %expr)
(do
(println* (fmt "Assertion '%s' failed at line %d, column %d in file %s" %(str expr) %(line) %(column) %(file)))
(System.abort))))
(doc assert "Crash the program with an error message unless the expression evaluates to 'true'. Supports an optional custom message.")
(defmacro assert [expr :rest msg]
(let [has-msg (> (length msg) 0)]
(if has-msg
(let [custom-msg (car msg)]
`(unless (= true %expr)
(let [msg-val (str %custom-msg)]
(do
(println* (fmt "Assertion '%s' failed: %s at line %d, column %d in file %s" %(str expr) &msg-val %(eval `(line %expr)) %(eval `(column %expr)) %(eval `(file %expr))))
(System.abort)))))
`(unless (= true %expr)
(do
(println* (fmt "Assertion '%s' failed at line %d, column %d in file %s" %(str expr) %(eval `(line %expr)) %(eval `(column %expr)) %(eval `(file %expr))))
(System.abort))))))
16 changes: 0 additions & 16 deletions core/Dynamic.carp
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Expand Up @@ -73,22 +73,6 @@ integers [`imod`](#imod).")
(defndynamic tail [s]
(String.suffix s 1))
)

(defmodule Debug
(doc trace "prints the value of an expression to `stdout`, then returns its value.")
(defmacro trace [x]
(let [sym (gensym)]
`(let-do [%sym %x]
; we use eval here to ensure we resolve the symbol before putting it
; into file, line, and column
(macro-log
%(eval `(file %x)) ":"
%(eval `(line %x)) ":"
%(eval `(column %x)) ": "
%sym)
%sym))
)
)
)


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11 changes: 11 additions & 0 deletions test/trace_assert_check.carp
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@@ -0,0 +1,11 @@
;; This file verifies the improved 'trace' and 'assert' macros in core/Debug.carp

(defn main []
(let [x (Debug.trace (+ 10 20))

@eriksvedang eriksvedang Aug 24, 2026

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Is the output from these trace calls checked somewhere?

@sqrew sqrew Aug 24, 2026

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No, you're probably right that it should be though. I didn't think of that!!

@eriksvedang eriksvedang Aug 25, 2026

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Should be doable if you add it to the tests that check their output.

@sqrew sqrew Aug 31, 2026

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will do

@sqrew sqrew Aug 31, 2026

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Hey @eriksvedang! I looked into adding the output check to the produces-output/ suite, but I ran into a bit of a snag with how trace resolves paths.

Because the macro uses (file) under the hood, it evaluates to the absolute path of the file at compile time. If I add it to produces-output, the .expected file would need my hardcoded local path (e.g., /home/.../Carp/test/...) and
would instantly fail on GitHub Actions when the CI runner checks it out to a different directory.

I could write a custom shell script to sanitize $PWD from the test output, but since the rest of the test suite cleanly uses execute.sh, I figured it's better to avoid polluting the test harnesses with one-off hacks. Because of this,
the test currently just executes the macro to ensure it compiles and evaluates properly without crashing. Let me know if you'd still prefer me to add a path-sanitizing hack to the test scripts though!

@eriksvedang eriksvedang Sep 1, 2026

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I see. Does setting file-path-print-length to short work in this context?

@sqrew sqrew Sep 1, 2026

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that is exactly the correct way to have solved this. I didn't think of that at all. Nice catch

y (Debug.trace @"hello")]
(do
(assert (= x 30))
(assert (= x 30) "x must be 30")
;; Print success message
(IO.println "All test assertions passed successfully!")
())))
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