add unnessary_else

Author: myfreess

e2etests/BUILTIN_RULES.md

@@ -47,6 +47,21 @@ source:
 3 >   inspect(1, content="1")
 4 | }
 
+testdata/builtin-rules-all/unnessary_else.mbt:3:3-6:12
+rule: moonbitlang/unnessary_else
+description:
+  Found an if expression whose else branch is empty or only returns ().
+  Prefer omitting the unnecessary else branch.
+source:
+1 | ///|
+2 | fn unnecessary_empty_else(flag : Bool) -> Unit {
+3 >   if flag {
+4 >     prepare()
+5 >     finish()
+6 >   } else {}
+7 | }
+8 | ///|
+
 testdata/builtin-rules-all/inspect_boolean.mbt:3:3-3:32
 rule: moonbitlang/inspect_boolean
 description:
@@ -118,6 +133,7 @@ $ cd "$TESTDIR"/.. && moonrun "$TESTDIR"/moongrep.wasm -- scan --output-json --e
 {"file":"testdata/builtin-rules-all/catch_all.mbt","rule_id":"moonbitlang/catch_all","description":"Single catch arm handles every error, which can hide unexpected failures.\nPrefer matching only the specific error cases that can be recovered from.","range":{"start":{"line":3,"column":3},"end":{"line":5,"column":4}},"matched_source":"try risky() catch {\n    _ => recover()\n  }","source_context":[{"line":1,"text":"///|","is_match":false},{"line":2,"text":"async fn catches_everything(_) -> Unit {","is_match":false},{"line":3,"text":"  try risky() catch {","is_match":true},{"line":4,"text":"    _ => recover()","is_match":true},{"line":5,"text":"  }","is_match":true},{"line":6,"text":"}","is_match":false}]}
 {"file":"testdata/builtin-rules-all/match_option.mbt","rule_id":"moonbitlang/match_option","description":"Found an Option value handled with match over Some and None.\nPrefer if + is for simple Option checks.","range":{"start":{"line":3,"column":3},"end":{"line":11,"column":4}},"matched_source":"match value {\n    Some(inner) => {\n      let prepared = prepare(inner)\n      let validated = validate(prepared)\n      let normalized = normalize(validated)\n      finish(normalized)\n    }\n    None => false\n  }","source_context":[{"line":1,"text":"///|","is_match":false},{"line":2,"text":"fn option_match(value : Int?) -> Bool {","is_match":false},{"line":3,"text":"  match value {","is_match":true},{"line":4,"text":"    Some(inner) => {","is_match":true},{"line":5,"text":"      let prepared = prepare(inner)","is_match":true},{"line":6,"text":"      let validated = validate(prepared)","is_match":true},{"line":7,"text":"      let normalized = normalize(validated)","is_match":true},{"line":8,"text":"      finish(normalized)","is_match":true},{"line":9,"text":"    }","is_match":true},{"line":10,"text":"    None => false","is_match":true},{"line":11,"text":"  }","is_match":true},{"line":12,"text":"}","is_match":false}]}
 {"file":"testdata/builtin-rules-all/inspect_number.mbt","rule_id":"moonbitlang/inspect_number","description":"Found inspect() snapshots whose expected value is a plain number.\nPrefer numeric assertions for numeric checks.","range":{"start":{"line":3,"column":3},"end":{"line":3,"column":26}},"matched_source":"inspect(1, content=\"1\")","source_context":[{"line":1,"text":"///|","is_match":false},{"line":2,"text":"fn number_snapshot() -> Unit {","is_match":false},{"line":3,"text":"  inspect(1, content=\"1\")","is_match":true},{"line":4,"text":"}","is_match":false}]}
+{"file":"testdata/builtin-rules-all/unnessary_else.mbt","rule_id":"moonbitlang/unnessary_else","description":"Found an if expression whose else branch is empty or only returns ().\nPrefer omitting the unnecessary else branch.","range":{"start":{"line":3,"column":3},"end":{"line":6,"column":12}},"matched_source":"if flag {\n    prepare()\n    finish()\n  } else {}","source_context":[{"line":1,"text":"///|","is_match":false},{"line":2,"text":"fn unnecessary_empty_else(flag : Bool) -> Unit {","is_match":false},{"line":3,"text":"  if flag {","is_match":true},{"line":4,"text":"    prepare()","is_match":true},{"line":5,"text":"    finish()","is_match":true},{"line":6,"text":"  } else {}","is_match":true},{"line":7,"text":"}","is_match":false},{"line":8,"text":"///|","is_match":false}]}
 {"file":"testdata/builtin-rules-all/inspect_boolean.mbt","rule_id":"moonbitlang/inspect_boolean","description":"Found inspect(), debug_inspect(), or json_inspect() snapshots whose expected value is true or false.\nPrefer assert_true(...) or assert_false(...) for boolean checks.","range":{"start":{"line":3,"column":3},"end":{"line":3,"column":32}},"matched_source":"inspect(flag, content=\"true\")","source_context":[{"line":1,"text":"///|","is_match":false},{"line":2,"text":"fn boolean_snapshot(flag : Bool) -> Unit {","is_match":false},{"line":3,"text":"  inspect(flag, content=\"true\")","is_match":true},{"line":4,"text":"}","is_match":false}]}
 {"file":"testdata/builtin-rules-all/cstyle_forward_simple_forloop.mbt","rule_id":"moonbitlang/cstyle_forward_simple_forloop","description":"C-style forward for loops that can be rewritten as simple for-in loops.","range":{"start":{"line":3,"column":3},"end":{"line":5,"column":4}},"matched_source":"for i = 0; i < limit; i = i + 1 {\n    tick()\n  }","source_context":[{"line":1,"text":"///|","is_match":false},{"line":2,"text":"fn forward_simple_loop(limit : Int) -> Unit {","is_match":false},{"line":3,"text":"  for i = 0; i < limit; i = i + 1 {","is_match":true},{"line":4,"text":"    tick()","is_match":true},{"line":5,"text":"  }","is_match":true},{"line":6,"text":"}","is_match":false}]}
 {"file":"testdata/builtin-rules-all/cstyle_backward_simple_forloop.mbt","rule_id":"moonbitlang/cstyle_backward_simple_forloop","description":"C-style backward for loops that can be rewritten as simple for-in loops.","range":{"start":{"line":3,"column":3},"end":{"line":5,"column":4}},"matched_source":"for i = limit; i > 0; i = i - 1 {\n    tick_back()\n  }","source_context":[{"line":1,"text":"///|","is_match":false},{"line":2,"text":"fn backward_simple_loop(limit : Int) -> Unit {","is_match":false},{"line":3,"text":"  for i = limit; i > 0; i = i - 1 {","is_match":true},{"line":4,"text":"    tick_back()","is_match":true},{"line":5,"text":"  }","is_match":true},{"line":6,"text":"}","is_match":false}]}

rule/builtin/builtin.mbt

@@ -41,6 +41,10 @@ fn builtin_rule_sources() -> Array[BuiltinRuleSource] {
       path: "builtin/moonbitlang/match_option.yaml",
       yaml: @moonbitlang_rules.match_option_yaml,
     },
+    {
+      path: "builtin/moonbitlang/unnessary_else.yaml",
+      yaml: @moonbitlang_rules.unnessary_else_yaml,
+    },
     {
       path: "builtin/moonbitlang/cstyle_forward_simple_forloop.yaml",
       yaml: @moonbitlang_rules.cstyle_forward_simple_forloop_yaml,

rule/builtin/builtin_test.mbt

@@ -13,6 +13,7 @@ test "builtin rules load moonbitlang rules" {
       #|  "moonbitlang/inspect_boolean",
       #|  "moonbitlang/inspect_number",
       #|  "moonbitlang/match_option",
+      #|  "moonbitlang/unnessary_else",
       #|  "moonbitlang/cstyle_forward_simple_forloop",
       #|  "moonbitlang/cstyle_backward_simple_forloop",
       #|  "moonbitlang/cstyle_forward_array_iteration",

rule/internal/rules/moonbitlang/moon.pkg

@@ -19,6 +19,12 @@ dev_build(
 
 dev_build(rule: "embed", input: "match_option.yaml", output: "match_option.mbt")
 
+dev_build(
+  rule: "embed",
+  input: "unnessary_else.yaml",
+  output: "unnessary_else.mbt",
+)
+
 dev_build(
   rule: "embed",
   input: "cstyle_forward_simple_forloop.yaml",

rule/internal/rules/moonbitlang/pkg.generated.mbti

@@ -18,6 +18,8 @@ pub let inspect_number_yaml : String
 
 pub let match_option_yaml : String
 
+pub let unnessary_else_yaml : String
+
 // Errors
 
 // Types and methods

rule/internal/rules/moonbitlang/unnessary_else.mbt

@@ -0,0 +1,24 @@
+// Generated by moonbit-community/embed from ./rule/internal/rules/moonbitlang/unnessary_else.yaml.
+
+///|
+let _embed_unnessary_else_yaml : String =
+  #|id: unnessary_else
+  #|description: |
+  #|  Found an if expression whose else branch is empty or only returns ().
+  #|  Prefer omitting the unnecessary else branch.
+  #|
+  #|patterns:
+  #|  - shape: |
+  #|      if $_ {
+  #|        $_
+  #|      } else {
+  #|        ()
+  #|      }
+  #|  - shape: |
+  #|      if $_ {
+  #|        $_
+  #|      } else {}
+  #|
+
+///|
+pub let unnessary_else_yaml : String = _embed_unnessary_else_yaml

rule/internal/rules/moonbitlang/unnessary_else.yaml

@@ -0,0 +1,16 @@
+id: unnessary_else
+description: |
+  Found an if expression whose else branch is empty or only returns ().
+  Prefer omitting the unnecessary else branch.
+
+patterns:
+  - shape: |
+      if $_ {
+        $_
+      } else {
+        ()
+      }
+  - shape: |
+      if $_ {
+        $_
+      } else {}

testdata/builtin-rules-all/unnessary_else.mbt

@@ -0,0 +1,11 @@
+///|
+fn unnecessary_empty_else(flag : Bool) -> Unit {
+  if flag {
+    prepare()
+    finish()
+  } else {}
+}
+///|
+fn non_unit_else(flag : Bool) -> Unit {
+  ignore(if flag { first() } else { second() })
+}