add the first batch of commands to standard library

amtoine · amtoine · commit e730176f3bc0 · 2023-02-21T11:10:37.000+01:00
This commit implements the few commands we talked about in the
dedicated discord channel, #standard-library:
- the `assert` familly with a private helper `_assert`
- a version of the `match` statement
diff --git a/crates/nu-utils/src/sample_config/std.nu b/crates/nu-utils/src/sample_config/std.nu
@@ -0,0 +1,124 @@
+def _assert [
+    cond: bool
+    msg: string
+] {
+    if not $cond {
+        error make {msg: $msg}
+    }
+}
+
+# ```nushell
+# >_ assert ($a == 3)
+# >_ assert ($a != 3)
+# Error:
+#   × condition given to `assert` does not hold
+#    ╭─[entry #12:5:1]
+#  5 │     if not $cond {
+#  6 │         error make {msg: $msg}
+#    ·         ─────┬────
+#    ·              ╰── originates from here
+#  7 │     }
+#    ╰────
+# ```
+export def assert [cond: bool] {
+    _assert $cond "condition given to `assert` does not hold"
+}
+
+# ```nushell
+# >_ assert_eq $a "a string"
+# Error:
+#   × left and right operand of `assert_eq` should have the same type
+#    ╭─[entry #12:5:1]
+#  5 │     if not $cond {
+#  6 │         error make {msg: $msg}
+#    ·         ─────┬────
+#    ·              ╰── originates from here
+#  7 │     }
+#    ╰────
+#
+# >_ assert_eq $a 3
+# >_ assert_eq $a 1
+# Error:
+#   × left is not equal to right
+#    ╭─[entry #12:5:1]
+#  5 │     if not $cond {
+#  6 │         error make {msg: $msg}
+#    ·         ─────┬────
+#    ·              ╰── originates from here
+#  7 │     }
+#    ╰────
+# ```
+export def assert_eq [left: any, right: any] {
+    _assert (($left | describe) == ($right | describe)) $"left and right operand of `assert_eq` should have the same type"
+    _assert ($left == $right) "left is not equal to right"
+}
+
+# ```nushell
+# >_ assert_ne $a "a string"
+# Error:
+#   × left and right operand of `assert_eq` should have the same type
+#    ╭─[entry #12:5:1]
+#  5 │     if not $cond {
+#  6 │         error make {msg: $msg}
+#    ·         ─────┬────
+#    ·              ╰── originates from here
+#  7 │     }
+#    ╰────
+#
+# >_ assert_ne $a 1
+# >_ assert_ne $a 3
+# Error:
+#   × left is equal to right
+#    ╭─[entry #12:5:1]
+#  5 │     if not $cond {
+#  6 │         error make {msg: $msg}
+#    ·         ─────┬────
+#    ·              ╰── originates from here
+#  7 │     }
+#    ╰────
+# ```
+export def assert_ne [left: any, right: any] {
+    _assert (($left | describe) == ($right | describe)) $"left and right operand of `assert_eq` should have the same type"
+    _assert ($left != $right) "left is equal to right"
+}
+
+# ```nushell
+# >_ let branches = {
+# )))     1: { print "this is the 1st branch"}
+# )))     2: { print "this is the 2nd branch" }
+# )))     3: { print "this is the 3rd branch" }
+# )))     4: { print "this is the 4th branch" }
+# ))) }
+#
+# >_ match 1 $branches
+# ))) match 2 $branches
+# ))) match 3 $branches
+# ))) match 4 $branches
+# ))) match 5 $branches
+# this is the 1st branch
+# this is the 2nd branch
+# this is the 3rd branch
+# this is the 4th branch
+#
+# >_ match 1 $branches { "this is the default branch" }
+# ))) match 2 $branches { "this is the default branch" }
+# ))) match 3 $branches { "this is the default branch" }
+# ))) match 4 $branches { "this is the default branch" }
+# ))) match 5 $branches { "this is the default branch" }
+# this is the 1st branch
+# this is the 2nd branch
+# this is the 3rd branch
+# this is the 4th branch
+# this is the default branch
+# ```
+export def match [
+    input:string
+    matchers:record
+    default?: block
+] {
+    if (($matchers | get -i $input) != null) {
+         $matchers | get $input | do $in
+    } else if ($default != null) {
+        do $default
+    }
+}
