Ignore unique constraint on drop constraint (#161)

Ignore rule failures on `DROP CONSTRAINT...` for _disallowed-unique-constraint_ and _adding-serial-primary-key-field_. 

When running `squawk` against the recommended usage,

```
CREATE UNIQUE INDEX CONCURRENTLY dist_id_temp_idx ON distributors (dist_id);
ALTER TABLE distributors DROP CONSTRAINT distributors_pkey,
    ADD CONSTRAINT distributors_pkey PRIMARY KEY USING INDEX dist_id_temp_idx;
```

we still get a warning.

Author: qoelet

linter/src/lib.rs

@@ -188,7 +188,7 @@ lazy_static! {
         func: prefer_robust_stmts,
         messages: vec![
             ViolationMessage::Help(
-                "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statment supports it.".into()
+                "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statement supports it.".into()
             ),
         ]
     },

linter/src/rules/adding_primary_key_constraint.rs

@@ -1,6 +1,6 @@
 use crate::violations::{RuleViolation, RuleViolationKind};
 use squawk_parser::ast::{
-    AlterTableCmds, AlterTableDef, ColumnDefConstraint, ConstrType, RootStmt, Stmt,
+    AlterTableCmds, AlterTableDef, AlterTableType, ColumnDefConstraint, ConstrType, RootStmt, Stmt,
 };
 
 #[must_use]
@@ -10,10 +10,26 @@ pub fn adding_primary_key_constraint(tree: &[RootStmt]) -> Vec<RuleViolation> {
         match &raw_stmt.stmt {
             Stmt::AlterTableStmt(stmt) => {
                 for AlterTableCmds::AlterTableCmd(cmd) in &stmt.cmds {
-                    match &cmd.def {
-                        Some(AlterTableDef::ColumnDef(def)) => {
+                    match (&cmd.def, &cmd.subtype) {
+                        (
+                            Some(AlterTableDef::Constraint(constraint)),
+                            AlterTableType::AddConstraint,
+                        ) => {
+                            if constraint.contype == ConstrType::Primary
+                                && constraint.indexname.is_none()
+                            {
+                                errs.push(RuleViolation::new(
+                                    RuleViolationKind::AddingSerialPrimaryKeyField,
+                                    raw_stmt.into(),
+                                    None,
+                                ));
+                            }
+                        }
+                        (Some(AlterTableDef::ColumnDef(def)), _) => {
                             for ColumnDefConstraint::Constraint(constraint) in &def.constraints {
-                                if constraint.contype == ConstrType::Primary {
+                                if constraint.contype == ConstrType::Primary
+                                    && constraint.indexname.is_none()
+                                {
                                     errs.push(RuleViolation::new(
                                         RuleViolationKind::AddingSerialPrimaryKeyField,
                                         raw_stmt.into(),
@@ -22,15 +38,6 @@ pub fn adding_primary_key_constraint(tree: &[RootStmt]) -> Vec<RuleViolation> {
                                 }
                             }
                         }
-                        Some(AlterTableDef::Constraint(constraint)) => {
-                            if constraint.contype == ConstrType::Primary {
-                                errs.push(RuleViolation::new(
-                                    RuleViolationKind::AddingSerialPrimaryKeyField,
-                                    raw_stmt.into(),
-                                    None,
-                                ));
-                            }
-                        }
                         _ => continue,
                     }
                 }

linter/src/rules/disallow_unique_constraint.rs

@@ -1,6 +1,8 @@
 use crate::rules::utils::tables_created_in_transaction;
 use crate::violations::{RuleViolation, RuleViolationKind};
-use squawk_parser::ast::{AlterTableCmds, AlterTableDef, ConstrType, RelationKind, RootStmt, Stmt};
+use squawk_parser::ast::{
+    AlterTableCmds, AlterTableDef, AlterTableType, ConstrType, RelationKind, RootStmt, Stmt,
+};
 
 #[must_use]
 pub fn disallow_unique_constraint(tree: &[RootStmt]) -> Vec<RuleViolation> {
@@ -12,8 +14,11 @@ pub fn disallow_unique_constraint(tree: &[RootStmt]) -> Vec<RuleViolation> {
                 let RelationKind::RangeVar(range) = &stmt.relation;
                 let tbl_name = &range.relname;
                 for AlterTableCmds::AlterTableCmd(cmd) in &stmt.cmds {
-                    match &cmd.def {
-                        Some(AlterTableDef::Constraint(constraint)) => {
+                    match (&cmd.def, &cmd.subtype) {
+                        (
+                            Some(AlterTableDef::Constraint(constraint)),
+                            AlterTableType::AddConstraint,
+                        ) => {
                             if !tables_created.contains(tbl_name)
                                 && constraint.contype == ConstrType::Unique
                                 && constraint.indexname.is_none()
@@ -54,6 +59,10 @@ mod test_rules {
     fn test_adding_unique_constraint() {
         let bad_sql = r#"
 ALTER TABLE table_name ADD CONSTRAINT field_name_constraint UNIQUE (field_name);
+   "#;
+
+        let ignored_sql = r#"
+ALTER TABLE table_name DROP CONSTRAINT field_name_constraint;
    "#;
 
         let ok_sql = r#"
@@ -63,15 +72,16 @@ ADD CONSTRAINT distributors_pkey PRIMARY KEY USING INDEX dist_id_temp_idx;
    "#;
 
         assert_debug_snapshot!(check_sql(bad_sql, &["prefer-robust-stmts".into()]));
+        assert_debug_snapshot!(check_sql(ignored_sql, &["prefer-robust-stmts".into()]));
         assert_debug_snapshot!(check_sql(ok_sql, &["prefer-robust-stmts".into()]));
     }
 
-    /// Creating a UNQIUE constraint from an existing index should be considered
+    /// Creating a UNIQUE constraint from an existing index should be considered
     /// safe
     #[test]
     fn test_unique_constraint_ok() {
         let sql = r#"
-CREATE UNIQUE INDEX CONCURRENTLY "legacy_questiongrouppg_mongo_id_1f8f47d9_uniq_idx" 
+CREATE UNIQUE INDEX CONCURRENTLY "legacy_questiongrouppg_mongo_id_1f8f47d9_uniq_idx"
     ON "legacy_questiongrouppg" ("mongo_id");
 ALTER TABLE "legacy_questiongrouppg" ADD CONSTRAINT "legacy_questiongrouppg_mongo_id_1f8f47d9_uniq" UNIQUE USING INDEX "legacy_questiongrouppg_mongo_id_1f8f47d9_uniq_idx";
         "#;

linter/src/rules/prefer_robust_stmts.rs

@@ -216,7 +216,7 @@ ALTER TABLE "core_foo" ADD COLUMN "answer_id" integer NULL;
                     },
                     messages: [
                         Help(
-                            "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statment supports it.",
+                            "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statement supports it.",
                         ),
                     ],
                 },
@@ -240,7 +240,7 @@ CREATE INDEX CONCURRENTLY "core_foo_idx" ON "core_foo" ("answer_id");
                     },
                     messages: [
                         Help(
-                            "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statment supports it.",
+                            "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statement supports it.",
                         ),
                     ],
                 },
@@ -264,7 +264,7 @@ CREATE TABLE "core_bar" ( "id" serial NOT NULL PRIMARY KEY, "bravo" text NOT NUL
                     },
                     messages: [
                         Help(
-                            "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statment supports it.",
+                            "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statement supports it.",
                         ),
                     ],
                 },
@@ -288,7 +288,7 @@ ALTER TABLE "core_foo" DROP CONSTRAINT "core_foo_idx";
                     },
                     messages: [
                         Help(
-                            "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statment supports it.",
+                            "Consider wrapping in a transaction or adding a IF NOT EXISTS clause if the statement supports it.",
                         ),
                     ],
                 },

linter/src/rules/snapshots/squawk_linter__rules__adding_primary_key_constraint__test_rules__plain_primary_key-2.snap

@@ -3,23 +3,5 @@ source: linter/src/rules/adding_primary_key_constraint.rs
 expression: "check_sql(ok_sql, &[\"prefer-robust-stmts\".into()])"
 ---
 Ok(
-    [
-        RuleViolation {
-            kind: AddingSerialPrimaryKeyField,
-            span: Span {
-                start: 0,
-                len: Some(
-                    75,
-                ),
-            },
-            messages: [
-                Note(
-                    "Adding a PRIMARY KEY constraint results in locks and table rewrites",
-                ),
-                Help(
-                    "Add the PRIMARY KEY constraint USING an index.",
-                ),
-            ],
-        },
-    ],
+    [],
 )

linter/src/rules/snapshots/squawk_linter__rules__disallow_unique_constraint__test_rules__adding_unique_constraint-2.snap

@@ -3,23 +3,5 @@ source: linter/src/rules/disallow_unique_constraint.rs
 expression: "check_sql(ok_sql, &[\"prefer-robust-stmts\".into()])"
 ---
 Ok(
-    [
-        RuleViolation {
-            kind: AddingSerialPrimaryKeyField,
-            span: Span {
-                start: 77,
-                len: Some(
-                    134,
-                ),
-            },
-            messages: [
-                Note(
-                    "Adding a PRIMARY KEY constraint results in locks and table rewrites",
-                ),
-                Help(
-                    "Add the PRIMARY KEY constraint USING an index.",
-                ),
-            ],
-        },
-    ],
+    [],
 )

linter/src/rules/snapshots/squawk_linter__rules__disallow_unique_constraint__test_rules__adding_unique_constraint-3.snap

@@ -0,0 +1,7 @@
+---
+source: linter/src/rules/disallow_unique_constraint.rs
+expression: "check_sql(ignored_sql, &[\"prefer-robust-stmts\".into()])"
+---
+Ok(
+    [],
+)