add support for pulling values from arrays and slices. (#50)

* add support for pulling values from arrays and slices. Switch to stackerr for errors. Rename proteus.ProteusError to proteus.Error and add Unwrap() support.

* add readme info on nested access. Add test to validate that it works.

Author: jonbodner

README.md

@@ -71,6 +71,37 @@ For insert/updates, return types can be:
 - an int64 that indicates the number of rows affected
 - an int64 that indicates the number of rows affected and an error
 
+The `proq` struct tag stores the query. You place variable substitutions between `:` s. Proteus allows you
+to refer to fields in maps and structs, as well as elements in arrays or slices using `.` as a path separator. If you have a
+struct like this:
+
+```go
+type Person struct {
+    Name string
+    Address Address
+    Pets []Pet
+} 
+
+type Pet struct {
+    Name string
+    Species string
+}
+
+type Address struct {
+    Street string
+    City string
+    State string
+}
+```
+You can write a query like this:
+
+```
+insert into person(name, city, pet1_name, pet2_name) values (:p.Name:, :p.Address.City:, :p.Pets.0.Name:, :p.Pets.1.Name:)
+```
+
+Note that the index for an array or slice must be an int literal and the key for a map must be a string.
+
+
 2\. If you want to map response fields to a struct, define a struct with struct tags to indicate the mapping:
 
 ```go

builder.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/jonbodner/proteus/logger"
 	"github.com/jonbodner/proteus/mapper"
+	"github.com/jonbodner/stackerr"
 )
 
 func buildNameOrderMap(paramOrder string, startPos int) map[string]int {
@@ -87,7 +88,7 @@ func buildFixedQueryAndParamOrder(c context.Context, query string, nameOrderMap
 			if inVar {
 				if len(curVar) == 0 {
 					//error! must have a something
-					return nil, nil, fmt.Errorf("empty variable declaration at position %d", k)
+					return nil, nil, stackerr.Errorf("empty variable declaration at position %d", k)
 				}
 				curVarS := string(curVar)
 				id, err := validIdentifier(c, curVarS)
@@ -103,7 +104,7 @@ func buildFixedQueryAndParamOrder(c context.Context, query string, nameOrderMap
 				//if it's a slice, then we put in the slice template syntax instead.
 
 				//get just the first part of the name, before any .
-				path := strings.SplitN(id, ".", 2)
+				path := strings.Split(id, ".")
 				paramName := path[0]
 				if paramPos, ok := nameOrderMap[paramName]; ok {
 					//if the path has more than one part, make sure that the type of the function parameter is map or struct
@@ -113,7 +114,7 @@ func buildFixedQueryAndParamOrder(c context.Context, query string, nameOrderMap
 						case reflect.Map, reflect.Struct:
 							//do nothing
 						default:
-							return nil, nil, fmt.Errorf("query Parameter %s has a path, but the incoming parameter is not a map or a struct", paramName)
+							return nil, nil, stackerr.Errorf("query Parameter %s has a path, but the incoming parameter is not a map or a struct", paramName)
 						}
 					}
 					pathType, err := mapper.ExtractType(c, paramType, path)
@@ -129,7 +130,7 @@ func buildFixedQueryAndParamOrder(c context.Context, query string, nameOrderMap
 					}
 					paramOrder = append(paramOrder, paramInfo{id, paramPos, isSlice})
 				} else {
-					return nil, nil, fmt.Errorf("query Parameter %s cannot be found in the incoming parameters", paramName)
+					return nil, nil, stackerr.Errorf("query Parameter %s cannot be found in the incoming parameters", paramName)
 				}
 
 				inVar = false
@@ -146,7 +147,7 @@ func buildFixedQueryAndParamOrder(c context.Context, query string, nameOrderMap
 		}
 	}
 	if inVar {
-		return nil, nil, fmt.Errorf("missing a closing : somewhere: %s", query)
+		return nil, nil, stackerr.Errorf("missing a closing : somewhere: %s", query)
 	}
 
 	queryString := out.String()
@@ -230,7 +231,7 @@ func addSlice(sliceName string) string {
 
 func validIdentifier(c context.Context, curVar string) (string, error) {
 	if strings.Contains(curVar, ";") {
-		return "", fmt.Errorf("; is not allowed in an identifier: %s", curVar)
+		return "", stackerr.Errorf("; is not allowed in an identifier: %s", curVar)
 	}
 	curVarB := []byte(curVar)
 
@@ -251,7 +252,7 @@ loop:
 		switch tok {
 		case token.EOF:
 			if first || lastPeriod {
-				return "", fmt.Errorf("identifiers cannot be empty or end with a .: %s", curVar)
+				return "", stackerr.Errorf("identifiers cannot be empty or end with a .: %s", curVar)
 			}
 			break loop
 		case token.SEMICOLON:
@@ -260,15 +261,15 @@ loop:
 			continue
 		case token.IDENT:
 			if !first && !lastPeriod && !lastFloat {
-				return "", fmt.Errorf(". missing between parts of an identifier: %s", curVar)
+				return "", stackerr.Errorf(". missing between parts of an identifier: %s", curVar)
 			}
 			first = false
 			lastPeriod = false
 			lastFloat = false
 			identifier += lit
 		case token.PERIOD:
 			if first || lastPeriod {
-				return "", fmt.Errorf("identifier cannot start with . or have two . in a row: %s", curVar)
+				return "", stackerr.Errorf("identifier cannot start with . or have two . in a row: %s", curVar)
 			}
 			lastPeriod = true
 			identifier += "."
@@ -280,28 +281,35 @@ loop:
 				first = false
 				continue
 			}
-			return "", fmt.Errorf("invalid character found in identifier: %s", curVar)
+			return "", stackerr.Errorf("invalid character found in identifier: %s", curVar)
 		case token.INT:
-			if !dollar {
-				return "", fmt.Errorf("invalid character found in identifier: %s", curVar)
+			if !dollar || first {
+				return "", stackerr.Errorf("invalid character found in identifier: %s", curVar)
 			}
 			identifier += lit
-			dollar = false
+			if dollar {
+				dollar = false
+			}
 		case token.FLOAT:
 			//this is weird. If we have $1.NAME, it will think that there's a FLOAT token with value 1.
 			//due to float support for exponents, if we have an E after the decimal point, the FLOAT token
-			//will include the E and any subsequent digits. Obviously, only valid for $ notation
-			if !dollar {
-				return "", fmt.Errorf("invalid character found in identifier: %s", curVar)
+			//will include the E and any subsequent digits.
+			// also a problem when walking array or slice references (values.0 is the 0th element in array values). This
+			// returns .0 as the lit value
+			//Only valid for $ notation and array/slice references.
+			if first {
+				return "", stackerr.Errorf("invalid character found in identifier: %s", curVar)
 			}
 			identifier += lit
-			dollar = false
+			if dollar {
+				dollar = false
+			}
 			lastFloat = true
 			if lit[len(lit)-1] == '.' {
 				lastPeriod = true
 			}
 		default:
-			return "", fmt.Errorf("invalid character found in identifier: %s", curVar)
+			return "", stackerr.Errorf("invalid character found in identifier: %s", curVar)
 		}
 	}
 	return identifier, nil

go.mod

@@ -4,9 +4,10 @@ go 1.15
 
 require (
 	github.com/go-sql-driver/mysql v1.5.0
-	github.com/google/go-cmp v0.3.1
+	github.com/google/go-cmp v0.4.0
 	github.com/jonbodner/dbtimer v0.0.0-20170410163237-7002f3758ae1
 	github.com/jonbodner/multierr v0.0.0-20200223210354-ace728439446
+	github.com/jonbodner/stackerr v1.0.0
 	github.com/lib/pq v1.8.0
 	github.com/pkg/profile v1.5.0
 	github.com/rickar/props v0.0.0-20170718221555-0b06aeb2f037

go.sum

@@ -3,12 +3,14 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/go-sql-driver/mysql v1.5.0 h1:ozyZYNQW3x3HtqT1jira07DN2PArx2v7/mN66gGcHOs=
 github.com/go-sql-driver/mysql v1.5.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=
-github.com/google/go-cmp v0.3.1 h1:Xye71clBPdm5HgqGwUkwhbynsUJZhDbS20FvLhQ2izg=
-github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=
+github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/jonbodner/dbtimer v0.0.0-20170410163237-7002f3758ae1 h1:mgFL7UFb88FOlSVgVoIRGJ4yKlkfp8KcXHqy7no+lEU=
 github.com/jonbodner/dbtimer v0.0.0-20170410163237-7002f3758ae1/go.mod h1:PjOlFbeJKs+4b2CvuN9FFF8Ed8cZ6FHWPb5tLK2QKOM=
 github.com/jonbodner/multierr v0.0.0-20200223210354-ace728439446 h1:3JlpjXILq02AhL5iNC/T6M+UwkKvcKq7/h0LPYP+R44=
 github.com/jonbodner/multierr v0.0.0-20200223210354-ace728439446/go.mod h1:BN5BmT8XsFrnRDB/uErUiXlda9UQs2YhrlFFtf74JaM=
+github.com/jonbodner/stackerr v1.0.0 h1:rAe+Fh13cfC9IGuKE4YWiVCzwt9zce9Saldpc8fYEIM=
+github.com/jonbodner/stackerr v1.0.0/go.mod h1:In1ShJr570PDuDHbYfymEQle+H7PgY9KpT+alyk0nEM=
 github.com/konsorten/go-windows-terminal-sequences v1.0.3 h1:CE8S1cTafDpPvMhIxNJKvHsGVBgn1xWYf1NbHQhywc8=
 github.com/konsorten/go-windows-terminal-sequences v1.0.3/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/lib/pq v1.8.0 h1:9xohqzkUwzR4Ga4ivdTcawVS89YSDVxXMa3xJX3cGzg=
@@ -29,3 +31,5 @@ golang.org/x/sys v0.0.0-20190422165155-953cdadca894 h1:Cz4ceDQGXuKRnVBDTS23GTn/p
 golang.org/x/sys v0.0.0-20190422165155-953cdadca894/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200828161417-c663848e9a16 h1:54u1berWyLujz9htI1BHtZpcCEYaYNUSDFLXMNDd7To=
 golang.org/x/sys v0.0.0-20200828161417-c663848e9a16/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

mapper/extract.go

@@ -2,44 +2,52 @@ package mapper
 
 import (
 	"context"
-	"errors"
+	"database/sql/driver"
 	"fmt"
 	"reflect"
-
-	"database/sql/driver"
+	"strconv"
 
 	"github.com/jonbodner/proteus/logger"
+	"github.com/jonbodner/stackerr"
 )
 
 func ExtractType(c context.Context, curType reflect.Type, path []string) (reflect.Type, error) {
 	// error case path length == 0
 	if len(path) == 0 {
-		return nil, errors.New("cannot extract type; no path remaining")
+		return nil, stackerr.New("cannot extract type; no path remaining")
 	}
 	ss := fromPtrType(curType)
 	// base case path length == 1
 	if len(path) == 1 {
 		return ss, nil
 	}
 	// length > 1, find a match for path[1], and recurse
-	if ss.Kind() == reflect.Map {
+	switch ss.Kind() {
+	case reflect.Map:
 		//give up -- we can't figure out what's in the map, so just return the type of the value
 		return ss.Elem(), nil
+	case reflect.Struct:
+		//make sure the field exists
+		if f, exists := ss.FieldByName(path[1]); exists {
+			return ExtractType(c, f.Type, path[1:])
+		}
+		return nil, stackerr.New("cannot find the type; no such field " + path[1])
+	case reflect.Array, reflect.Slice:
+		// handle slices and arrays
+		_, err := strconv.Atoi(path[1])
+		if err != nil {
+			return nil, stackerr.Errorf("invalid index: %s :%w", path[1], err)
+		}
+		return ExtractType(c, ss.Elem(), path[1:])
+	default:
+		return nil, stackerr.New("cannot find the type for the subfield of anything other than a map, struct, slice, or array")
 	}
-	if ss.Kind() != reflect.Struct {
-		return nil, errors.New("Cannot find the type for the subfield of anything other than a struct.")
-	}
-	//make sure the field exists
-	if f, exists := ss.FieldByName(path[1]); exists {
-		return ExtractType(c, f.Type, path[1:])
-	}
-	return nil, errors.New("cannot find the type; no such field " + path[1])
 }
 
 func Extract(c context.Context, s interface{}, path []string) (interface{}, error) {
 	// error case path length == 0
 	if len(path) == 0 {
-		return nil, errors.New("cannot extract value; no path remaining")
+		return nil, stackerr.New("cannot extract value; no path remaining")
 	}
 	// base case path length == 1
 	if len(path) == 1 {
@@ -52,29 +60,38 @@ func Extract(c context.Context, s interface{}, path []string) (interface{}, erro
 	// length > 1, find a match for path[1], and recurse
 	ss := fromPtr(s)
 	sv := reflect.ValueOf(ss)
-	if sv.Kind() == reflect.Map {
+	switch sv.Kind() {
+	case reflect.Map:
 		if sv.Type().Key().Kind() != reflect.String {
-			return nil, errors.New("cannot extract value; map does not have a string key")
+			return nil, stackerr.New("cannot extract value; map does not have a string key")
 		}
 		logger.Log(c, logger.DEBUG, fmt.Sprintln(path[1]))
 		logger.Log(c, logger.DEBUG, fmt.Sprintln(sv.MapKeys()))
 		v := sv.MapIndex(reflect.ValueOf(path[1]))
 		logger.Log(c, logger.DEBUG, fmt.Sprintln(v))
 		if !v.IsValid() {
-			return nil, errors.New("cannot extract value; no such map key " + path[1])
+			return nil, stackerr.New("cannot extract value; no such map key " + path[1])
 		}
 		return Extract(c, v.Interface(), path[1:])
-	}
-	if sv.Kind() == reflect.Struct {
+	case reflect.Struct:
 		//make sure the field exists
 		if _, exists := sv.Type().FieldByName(path[1]); !exists {
-			return nil, errors.New("cannot extract value; no such field " + path[1])
+			return nil, stackerr.New("cannot extract value; no such field " + path[1])
 		}
 
 		v := sv.FieldByName(path[1])
 		return Extract(c, v.Interface(), path[1:])
+	case reflect.Array, reflect.Slice:
+		// handle slices and arrays
+		pos, err := strconv.Atoi(path[1])
+		if err != nil {
+			return nil, stackerr.Errorf("invalid index: %s :%w", path[1], err)
+		}
+		v := sv.Index(pos)
+		return Extract(c, v.Interface(), path[1:])
+	default:
+		return nil, stackerr.New("cannot extract value; only maps and structs can have contained values")
 	}
-	return nil, errors.New("cannot extract value; only maps and structs can have contained values")
 }
 
 func fromPtr(s interface{}) interface{} {

mapper/extract_test.go

@@ -2,13 +2,13 @@ package mapper
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"reflect"
 	"testing"
 
 	"github.com/jonbodner/proteus/cmp"
 	"github.com/jonbodner/proteus/logger"
+	"github.com/jonbodner/stackerr"
 )
 
 func TestExtractPointer(t *testing.T) {
@@ -124,7 +124,7 @@ func TestExtractFail(t *testing.T) {
 		if err == nil {
 			t.Errorf("Expected an error %s, got none", msg)
 		}
-		eExp := errors.New(msg)
+		eExp := stackerr.New(msg)
 		if !cmp.Errors(err, eExp) {
 			t.Errorf("Expected error %s, got %s", eExp, err)
 		}