feat: implement if/then/else (#64)

Author: flrgh

lib/jsonschema.lua

@@ -1025,6 +1025,29 @@ generate_validator = function(ctx, schema)
     ctx:stmt('end')
   end
 
+  if schema['if'] then
+    ctx:stmt(          'do')
+    local validator = ctx:validator({ 'if' }, schema['if'])
+    ctx:stmt(sformat(  '  local matched = %s(%s)', validator, ctx:param(1)))
+    if schema['then'] then
+      ctx:stmt(        '  if matched then')
+      validator = ctx:validator({ 'then' }, schema['then'])
+      ctx:stmt(sformat('    if not %s(%s) then', validator, ctx:param(1)))
+      ctx:stmt(        '      return false, "then clause did not match"')
+      ctx:stmt(        '    end')
+      ctx:stmt(        '  end')
+    end
+    if schema['else'] then
+      ctx:stmt(        '  if not matched then')
+      validator = ctx:validator({ 'else' }, schema['else'])
+      ctx:stmt(sformat('    if not %s(%s) then', validator, ctx:param(1)))
+      ctx:stmt(        '      return false, "else clause did not match"')
+      ctx:stmt(        '    end')
+      ctx:stmt(        '  end')
+    end
+    ctx:stmt(          'end')
+  end
+
   if schema['not'] then
     local validator = ctx:validator({ 'not' }, schema['not'])
     ctx:stmt(sformat('if %s(%s) then', validator, ctx:param(1)))

t/draft7.lua

@@ -92,15 +92,13 @@ local supported = {
   'spec/JSON-Schema-Test-Suite/tests/draft7/format.json',
   'spec/JSON-Schema-Test-Suite/tests/draft7/const.json',
   'spec/JSON-Schema-Test-Suite/tests/draft7/contains.json',
+  'spec/JSON-Schema-Test-Suite/tests/draft7/if-then-else.json',
 
   -- ref
   'spec/JSON-Schema-Test-Suite/tests/draft7/ref.json',
   -- not support: an external resolver is required
   -- 'spec/JSON-Schema-Test-Suite/tests/draft7/refRemote.json',
   -- 'spec/JSON-Schema-Test-Suite/tests/draft7/definitions.json',
-
-  -- not support: todo
-  -- 'spec/JSON-Schema-Test-Suite/tests/draft7/if-then-else.json',
 }
 -- supported = {
 --   'spec/JSON-Schema-Test-Suite/tests/draft7/dependencies.json',